1
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Sameoto D. Beyond biomimicry - next generation applications of bioinspired adhesives from microfluidics to composites. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2024; 15:965-976. [PMID: 39136040 PMCID: PMC11318608 DOI: 10.3762/bjnano.15.79] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 07/11/2024] [Indexed: 08/15/2024]
Abstract
In this perspective article, Professor Dan Sameoto outlines his opinion on future opportunities in the field of biomimetic adhesives. Despite over twenty years of excellent academic work by groups all around the world in this subfield, the economic value and impact of these materials is somewhat underwhelming. The question for the field is whether it should have a scientific and engineering focus to create every greater performance and understanding of the materials and hope that "if we build it, they will come". Perhaps we should expand our concept on what could be the desirable end applications for such materials and focus efforts on finding better end applications in which these materials can truly shine; a few of those applications like microfluidics and composites are highlighted in this article. It is time for a next generation of research to look beyond biomimicry and look towards re-engineering applications to make use of these materials' unique properties in economically viable ways.
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Affiliation(s)
- Dan Sameoto
- Department of Mechanical Engineering, University of Alberta, Edmonton AB, T6G 1H9, Canada
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2
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Zhao J, Xia N, Zhang L. A review of bioinspired dry adhesives: from achieving strong adhesion to realizing switchable adhesion. BIOINSPIRATION & BIOMIMETICS 2024; 19:051003. [PMID: 38996419 DOI: 10.1088/1748-3190/ad62cf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 07/12/2024] [Indexed: 07/14/2024]
Abstract
In the early twenty-first century, extensive research has been conducted on geckos' ability to climb vertical walls with the advancement of microscopy technology. Unprecedented studies and developments have focused on the adhesion mechanism, structural design, preparation methods, and applications of bioinspired dry adhesives. Notably, strong adhesion that adheres to both the principles of contact splitting and stress uniform distribution has been discovered and proposed. The increasing popularity of flexible electronic skins, soft crawling robots, and smart assembly systems has made switchable adhesion properties essential for smart adhesives. These adhesives are designed to be programmable and switchable in response to external stimuli such as magnetic fields, thermal changes, electrical signals, light exposure as well as mechanical processes. This paper provides a comprehensive review of the development history of bioinspired dry adhesives from achieving strong adhesion to realizing switchable adhesion.
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Affiliation(s)
- Jinsheng Zhao
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin NT, Hong Kong Special Administrative Region of China 999077, People's Republic of China
| | - Neng Xia
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin NT, Hong Kong Special Administrative Region of China 999077, People's Republic of China
| | - Li Zhang
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin NT, Hong Kong Special Administrative Region of China 999077, People's Republic of China
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Li D, Li R, Yuan K, Chen A, Guo N, Xu C, Zhang W. In-Plane Combination of Micropillars with Distinct Aspect Ratios to Resist Overload-Induced Adhesion Failure. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2400972. [PMID: 38718307 PMCID: PMC11267270 DOI: 10.1002/advs.202400972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 04/10/2024] [Indexed: 07/25/2024]
Abstract
Bioinspired micropillar adhesives have shown broad application prospects in space capture and docking, due to their strong adhesion, good environmental adaptability, and reusability. However, when performing space missions, unavoidable contact collision with target objects may cause large deformation of the micropillars, resulting in the loss of adhesion ability. This study reports a novel micropillar adhesive through the in-plane combination of micropillars (IPCM) with different aspect ratios, consisting of small pillars for retaining strong adhesion and large ones for resisting overload-induced adhesion failure. It is demonstrated that the IPCM array can still maintain 85% of the adhesion peak after static large deformation compared to a general micropillar array composed of the same pillars. The impact of element size and layout of the IPCM, as well as detachment velocity on adhesion performance under high preload is discussed. Furthermore, finite element contact analysis qualitatively reproduces the experimentally observed micropillar deformations and attributes the overload-induced adhesion failure to the redistribution of surface normal stress. Finally, the potential application of the IPCM in dynamic capture is demonstrated on different objects. The proposed IPCM opens up new design concepts for practical applications of bioinspired adhesives in space capture and docking.
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Affiliation(s)
- Dongwu Li
- School of AstronauticsNorthwestern Polytechnical UniversityXi'an710072China
| | - Ruozhang Li
- State Key Laboratory of Mechanical System and VibrationSchool of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai200240China
| | - Kangbo Yuan
- School of MechanicsCivil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an710072China
| | - Ao Chen
- State Key Laboratory of Mechanical System and VibrationSchool of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai200240China
| | - Ning Guo
- School of AstronauticsNorthwestern Polytechnical UniversityXi'an710072China
| | - Chao Xu
- School of AstronauticsNorthwestern Polytechnical UniversityXi'an710072China
| | - Wenming Zhang
- State Key Laboratory of Mechanical System and VibrationSchool of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai200240China
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Zhu B, Tan D, Xiao K, Shi Z, Li G, Lei Y, Chen D, Liu S, Xue L. Micropillar with Radial Gradient Modulus Enables Robust Adhesion and Friction. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2310887. [PMID: 38409520 DOI: 10.1002/smll.202310887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 02/08/2024] [Indexed: 02/28/2024]
Abstract
The gradient modulus in beetle setae plays a critical role in allowing it to stand and walk on natural surfaces. Mimicking beetle setae to create a modulus gradient in microscale, especially in the direction of setae radius, can achieve reliable contact and thus strong adhesion. However, it remains highly challenging to achieve modulus gradient along radial directions in setae-like structures. Here, polydimethylsiloxane (PDMS) micropillar with radial gradient modulus, (termed GM), is successfully constructed by making use of the polymerization inhibitor in the photosensitive resin template. GM gains adhesion up to 84 kPa, which is 2.3 and 4.7 times of soft homogeneous micropillars (SH) and hard homogeneous micropillars (HH), respectively. The radial gradient modulus facilitates contact formation on various surfaces and shifts stress concentration from contact perimeter to the center, resulting in adhesion enhancement. Meanwhile, GM achieves strong friction of 8.1 mN, which is 1.2 and 2.6 times of SH and HH, respectively. Moreover, GM possesses high robustness, maintaining strong adhesion and friction after 400 cycles of tests. The work here not only provides a robust structure for strong adhesion and friction, but also establishes a strategy to create modulus gradient at micron-scale.
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Affiliation(s)
- Bo Zhu
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Di Tan
- Nanotechnology Center, School of Fashion and Textiles, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, 999077, China
| | - Kangjian Xiao
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Zhekun Shi
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Gang Li
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Yifeng Lei
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Daobing Chen
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Sheng Liu
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
| | - Longjian Xue
- The Institute of Technological Science, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China
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Luo C, Ma X, Zhang Y, Peng Y, Zhou Y, Zhao X, Zhang F. Multiscale Synergistic Gecko-Inspired Adhesive for Stable Adhesion under Varying Preload and Surface Roughness. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:9957-9964. [PMID: 38683042 DOI: 10.1021/acs.langmuir.4c00064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Abstract
Inspired by geckos, fibrillar microstructures hold great promise as controllable and reversible adhesives in the engineering field. However, enhancing the adhesion strength and stability of gecko-inspired adhesives (GIAs) under complex real-world contact conditions, such as rough surfaces and varying force fields, is crucial for its commercialization, yet further research is lacking. Here, we propose a hierarchically designed GIA, which features a silicone foam (SF) backing layer and a film-terminated fibrillar microstructure under a subtle multiscale design. This structure has been proven to have a "multiscale synergistic effect", allowing the material to maintain strong and stable adhesion to surfaces with changing normal pressures and roughness. Specifically, under a high load, the adhesive strength is 2 times more than that of conventional GIA, and it is 1.5 times stronger on rough surfaces compared to conventional GIA. Under high pressure and high surface roughness simultaneously, the adhesive strength is 3.3 times higher compared to conventional GIA. Our research demonstrates that the synergistic effect of multiscale biomimetic adhesion structures is highly effective in enhancing the adhesive strength of GIA under some harsh contact conditions.
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Affiliation(s)
- Chao Luo
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
| | - Xinguo Ma
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
- College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China
| | - Yaling Zhang
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
| | - Yan Peng
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
| | - Yi Zhou
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
| | - Xiuli Zhao
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
| | - Fengshun Zhang
- Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621900, Sichuan, China
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Kumar R, Rezapourian M, Rahmani R, Maurya HS, Kamboj N, Hussainova I. Bioinspired and Multifunctional Tribological Materials for Sliding, Erosive, Machining, and Energy-Absorbing Conditions: A Review. Biomimetics (Basel) 2024; 9:209. [PMID: 38667221 PMCID: PMC11048303 DOI: 10.3390/biomimetics9040209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 04/28/2024] Open
Abstract
Friction, wear, and the consequent energy dissipation pose significant challenges in systems with moving components, spanning various domains, including nanoelectromechanical systems (NEMS/MEMS) and bio-MEMS (microrobots), hip prostheses (biomaterials), offshore wind and hydro turbines, space vehicles, solar mirrors for photovoltaics, triboelectric generators, etc. Nature-inspired bionic surfaces offer valuable examples of effective texturing strategies, encompassing various geometric and topological approaches tailored to mitigate frictional effects and related functionalities in various scenarios. By employing biomimetic surface modifications, for example, roughness tailoring, multifunctionality of the system can be generated to efficiently reduce friction and wear, enhance load-bearing capacity, improve self-adaptiveness in different environments, improve chemical interactions, facilitate biological interactions, etc. However, the full potential of bioinspired texturing remains untapped due to the limited mechanistic understanding of functional aspects in tribological/biotribological settings. The current review extends to surface engineering and provides a comprehensive and critical assessment of bioinspired texturing that exhibits sustainable synergy between tribology and biology. The successful evolving examples from nature for surface/tribological solutions that can efficiently solve complex tribological problems in both dry and lubricated contact situations are comprehensively discussed. The review encompasses four major wear conditions: sliding, solid-particle erosion, machining or cutting, and impact (energy absorbing). Furthermore, it explores how topographies and their design parameters can provide tailored responses (multifunctionality) under specified tribological conditions. Additionally, an interdisciplinary perspective on the future potential of bioinspired materials and structures with enhanced wear resistance is presented.
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Affiliation(s)
- Rahul Kumar
- Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia; (M.R.); (H.S.M.); (N.K.); (I.H.)
| | - Mansoureh Rezapourian
- Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia; (M.R.); (H.S.M.); (N.K.); (I.H.)
| | - Ramin Rahmani
- CiTin–Centro de Interface Tecnológico Industrial, 4970-786 Arcos de Valdevez, Portugal;
- proMetheus–Instituto Politécnico de Viana do Castelo (IPVC), 4900-347 Viana do Castelo, Portugal
| | - Himanshu S. Maurya
- Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia; (M.R.); (H.S.M.); (N.K.); (I.H.)
- Department of Engineering Sciences and Mathematics, Luleå University of Technology, 97187 Luleå, Sweden
| | - Nikhil Kamboj
- Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia; (M.R.); (H.S.M.); (N.K.); (I.H.)
- Department of Mechanical and Materials Engineering, University of Turku, 20500 Turku, Finland
- TCBC–Turku Clinical Biomaterials Centre, Department of Biomaterials Science, Faculty of Medicine, Institute of Dentistry, University of Turku, 20014 Turku, Finland
| | - Irina Hussainova
- Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia; (M.R.); (H.S.M.); (N.K.); (I.H.)
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Liu Y, Wang H, Li J, Li P, Li S. Gecko-Inspired Controllable Adhesive: Structure, Fabrication, and Application. Biomimetics (Basel) 2024; 9:149. [PMID: 38534834 DOI: 10.3390/biomimetics9030149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 02/18/2024] [Accepted: 02/24/2024] [Indexed: 03/28/2024] Open
Abstract
The gecko can achieve flexible climbing on various vertical walls and even ceilings, which is closely related to its unique foot adhesion system. In the past two decades, the mechanism of the gecko adhesion system has been studied in-depth, and a verity of gecko-inspired adhesives have been proposed. In addition to its strong adhesion, its easy detachment is also the key to achieving efficient climbing locomotion for geckos. A similar controllable adhesion characteristic is also key to the research into artificial gecko-inspired adhesives. In this paper, the structures, fabrication methods, and applications of gecko-inspired controllable adhesives are summarized for future reference in adhesive development. Firstly, the controllable adhesion mechanism of geckos is introduced. Then, the control mechanism, adhesion performance, and preparation methods of gecko-inspired controllable adhesives are described. Subsequently, various successful applications of gecko-inspired controllable adhesives are presented. Finally, future challenges and opportunities to develop gecko-inspired controllable adhesive are presented.
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Affiliation(s)
- Yanwei Liu
- Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Ministry of Education, Xi'an University of Technology, Xi'an 710048, China
- School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China
| | - Hao Wang
- Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Ministry of Education, Xi'an University of Technology, Xi'an 710048, China
- School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China
| | - Jiangchao Li
- Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Ministry of Education, Xi'an University of Technology, Xi'an 710048, China
- School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China
| | - Pengyang Li
- Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Ministry of Education, Xi'an University of Technology, Xi'an 710048, China
- School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China
| | - Shujuan Li
- Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Ministry of Education, Xi'an University of Technology, Xi'an 710048, China
- School of Mechanical and Precision Instrument Engineering, Xi'an University of Technology, Xi'an 710048, China
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Li J, Yin F, Tian Y. Biomimetic Structure and Surface for Grasping Tasks. Biomimetics (Basel) 2024; 9:144. [PMID: 38534829 DOI: 10.3390/biomimetics9030144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 03/28/2024] Open
Abstract
Under water, on land, or in the air, creatures use a variety of grasping methods to hunt, avoid predators, or carry food. Numerous studies have been conducted to construct a bionic surface for grasping tasks. This paper reviews the typical biomimetic structures and surfaces (wedge-shaped surface, suction cup surface and thorn claw surface) for grasping scenarios. Initially, progress in gecko-inspired wedge-shaped adhesive surfaces is reviewed, encompassing the underlying mechanisms that involve tuning the contact area and peeling behavior. The applications of grippers utilizing this adhesive technology are also discussed. Subsequently, the suction force mechanisms and applications of surfaces inspired by octopus and remora suction cups are outlined. Moreover, this paper introduces the applications of robots incorporating the principles of beetle-inspired and bird-inspired thorn claw structures. Lastly, inspired by remoras' adhesive discs, a composite biomimetic adhesive surface is proposed. It integrates features from wedge-shaped, suction cup, and claw thorn surfaces, potentially surpassing the adaptability of basic bioinspired surfaces. This surface construction method offers a potential avenue to enhance adhesion capabilities with superior adaptability to surface roughness and curvature.
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Affiliation(s)
- Jingyang Li
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Fujie Yin
- Xingjian College, Tsinghua University, Beijing 100084, China
| | - Yu Tian
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
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Tan L, Chen Y, Fu W, Tian J, Wang Y, Li X, Zhou Y, Xia S, Liang M, Zou H. Bioinspired Microadhesives with Greatly Enhanced Reversible Adhesion Fabricated by Synthesized Silicone Elastomer with Increasing Phenyl Contents. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:13068-13075. [PMID: 37678181 DOI: 10.1021/acs.langmuir.3c01382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
We present a facile chemical method for fabricating bioinspired microadhesives with significant improved reversible adhesion strength. Four kinds of polysiloxane with gradient varying phenyl contents were synthesized and used to fabricate microadhesives. The chemical structures and mechanical properties, as well as surface properties of the four microadhesives, were confirmed and characterized by ATR-FTIR, DSC, XPS, low-field NMR, tensile tests, and SEM, respectively. The macroadhesion test results revealed that phenyl contents showed remarkable and positive impacts on the macroadhesion performance of microadhesives. The pull-off adhesion strength of microadhesives with 90% phenyl content (0.851 N/cm2) was nearly 300% higher than that of pure PDMS (0.309 N/cm2). The macroadhesion mechanism analysis demonstrates that a larger bulk energy dissipation caused by massive π-π interaction, as well as the hydrophobic interaction and van der Waals forces at the interface synergistically resulted in a significant enhancement of the adhesion performance. Our results demonstrate the remarkable impact of chemical structures on the adhesion of microadhesives, and it is conducive to the further improvement of adhesion properties of bioinspired microadhesives.
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Affiliation(s)
- Lei Tan
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Yukun Chen
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Wenxin Fu
- Key Laboratory of Science and Technology on High-tech Polymer Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Jinfeng Tian
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Yuan Wang
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Xiaohui Li
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Yilin Zhou
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Shuang Xia
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Mei Liang
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
| | - Huawei Zou
- The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China
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Zhang Z, He B, Han Q, He R, Ding Y, Han B, Ma ZC. Femtosecond Laser Direct Writing of Gecko-Inspired Switchable Adhesion Interfaces on a Flexible Substrate. MICROMACHINES 2023; 14:1742. [PMID: 37763905 PMCID: PMC10534918 DOI: 10.3390/mi14091742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 08/31/2023] [Accepted: 09/04/2023] [Indexed: 09/29/2023]
Abstract
Biomimetic switchable adhesion interfaces (BSAIs) with dynamic adhesion states have demonstrated significant advantages in micro-manipulation and bio-detection. Among them, gecko-inspired adhesives have garnered considerable attention due to their exceptional adaptability to extreme environments. However, their high adhesion strength poses challenges in achieving flexible control. Herein, we propose an elegant and efficient approach by fabricating three-dimensional mushroom-shaped polydimethylsiloxane (PDMS) micropillars on a flexible PDMS substrate to mimic the bending and stretching of gecko footpads. The fabrication process that employs two-photon polymerization ensures high spatial resolution, resulting in micropillars with exquisite structures and ultra-smooth surfaces, even for tip/stem ratios exceeding 2 (a critical factor for maintaining adhesion strength). Furthermore, these adhesive structures display outstanding resilience, enduring 175% deformation and severe bending without collapse, ascribing to the excellent compatibility of the micropillar's composition and physical properties with the substrate. Our BSAIs can achieve highly controllable adhesion force and rapid manipulation of liquid droplets through mechanical bending and stretching of the PDMS substrate. By adjusting the spacing between the micropillars, precise control of adhesion strength is achieved. These intriguing properties make them promising candidates for various applications in the fields of microfluidics, micro-assembly, flexible electronics, and beyond.
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Affiliation(s)
- Zhiang Zhang
- Department of Automation, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Bingze He
- Institute of Medical Robotics, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qingqing Han
- Department of Automation, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ruokun He
- Department of Automation, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yuxuan Ding
- Institute of Medical Robotics, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Bing Han
- Institute of Medical Robotics, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Zhuo-Chen Ma
- Department of Automation, Shanghai Jiao Tong University, Shanghai 200240, China
- Institute of Medical Robotics, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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Wang D, Hu H, Li S, Tian H, Fan W, Li X, Chen X, Taylor AC, Shao J. Sensing-triggered stiffness-tunable smart adhesives. SCIENCE ADVANCES 2023; 9:eadf4051. [PMID: 36921055 PMCID: PMC10017039 DOI: 10.1126/sciadv.adf4051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
Artificial dry adhesives have exhibited great potential in the field of robotics. However, there is still a wide gap between bioinspired adhesives and living tissues, especially regarding the surface adaptability and switching ability of attachment/detachment. Here, we propose a sensing-triggered stiffness-tunable smart adhesive material, combining the functions of muscle tissues and sensing nerves rather than traditional biomimetic adhesive strategy that only focuses on structural geometry. Authorized by real-time perception of the interface contact state, conformal contact, shape locking, and active releasing are achieved by adjusting the stiffness based on the magnetorheological effect. Because of the fast switching of the magnetic field, a millisecond-level attachment/detachment response is successfully achieved, breaking the bottleneck of adhesive materials for high-speed manipulation. The innovative design can be applied to any toe's surface structure, opening up a previously unknown avenue for the development of adhesive materials.
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Affiliation(s)
- Duorui Wang
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
- Frontier Institute of Science and Technology (FIST), Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Hong Hu
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
- Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Shuai Li
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Hongmiao Tian
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Wei Fan
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Xiangming Li
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
- Frontier Institute of Science and Technology (FIST), Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Xiaoliang Chen
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
- Frontier Institute of Science and Technology (FIST), Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
| | - Ambrose C. Taylor
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Jinyou Shao
- Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
- Frontier Institute of Science and Technology (FIST), Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
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12
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Shi Z, Zhu B, Wang Z, Xiao K, Wang Y, Xue L. Robust and Elevated Adhesion and Anisotropic Friction in a Bioinspired Bridged Micropillar Array. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3784-3791. [PMID: 36848498 DOI: 10.1021/acs.langmuir.3c00033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Bioinspired structured adhesives have promising applications in the fields of robotics, electronics, medical engineering, and so forth. The strong adhesion and friction as well as the durability of bioinspired hierarchical fibrillar adhesives are essential for their applications, which require fine submicrometer structures to stay stable during repeated use. Here, we develop a bioinspired bridged micropillars array (BP), which realizes a 2.18-fold adhesion and a 2.02-fold friction as compared to that of poly(dimethylsiloxane) (PDMS) original micropillar arrays. The aligned bridges offer BP strong anisotropic friction. The adhesion and friction of BP can be finely regulated by changing the modulus of the bridges. Moreover, BP shows strong adaptability to surface curvature (ranging from 0 to 800 m-1), excellent durability over 500 repeating cycles of attachment/detachment, and self-cleaning ability. This study presents a novel approach for designing robust structured adhesives with strong and anisotropic friction, which may find applications in areas such as climbing robots and cargo transportation.
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Affiliation(s)
- Zhekun Shi
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, Wuhan 430072, China
| | - Bo Zhu
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, Wuhan 430072, China
| | - Zhuo Wang
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, Wuhan 430072, China
| | - Kangjian Xiao
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, Wuhan 430072, China
| | - Yan Wang
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, Wuhan 430072, China
| | - Longjian Xue
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, Wuhan 430072, China
- Hubei Yangtze Memory Laboratories, Wuhan 430205, China
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13
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Duan W, Yu Z, Cui W, Zhang Z, Zhang W, Tian Y. Bio-inspired switchable soft adhesion for the boost of adhesive surfaces and robotics applications: A brief review. Adv Colloid Interface Sci 2023; 313:102862. [PMID: 36848868 DOI: 10.1016/j.cis.2023.102862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 02/10/2023] [Accepted: 02/17/2023] [Indexed: 02/22/2023]
Abstract
In nature, millions of creatures, such as geckos, tree frogs, octopuses, etc., have evolved fantastic switchable adhesion capabilities to climb swiftly on vertical even inverted surfaces or hunt for prey easily, adapting to harsh and unpredictable environments. Notably, these fascinating adhesive behaviors depend on interfacial forces (friction, van der Waals force, capillary force, vacuum suction, etc.), which primarily originate from the interactions between the soft micro/nanostructures evolved in the natural creatures and objects. Over the past few decades, these biological switchable adhesives have inspired scientists to explore and engineer desirable artificial adhesives. In this review, we summarized the state-of-the-art research on the ultra-fast adhesive motion of three types of biological organisms (gecko, tree frog, and octopus). Firstly, the basic adhesion principles in the three representative organisms, including micro/nanostructures, interfacial forces, and fundamental adhesion models, are reviewed. Then, we discussed the adhesion mechanisms of the prominent organisms from the perspective of soft contacts between micro/nanostructures and the substrates. Later, the mechanics-guided design principles of artificial adhesive surfaces, as well as the smart adhesion strategies, are summarized. The applications of these bio-inspired switchable adhesives are demonstrated, including wearable electronic devices, soft grippers, and climbing robots. The challenges and opportunities in this fast-growing field are also discussed.
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Affiliation(s)
- Weiwang Duan
- School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Zhilin Yu
- School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Wenhui Cui
- School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Zengxin Zhang
- School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Wenling Zhang
- School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
| | - Yu Tian
- State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
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14
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Sudersan P, Kappl M. Mechanisms of detachment in fibrillar adhesive systems. J Theor Biol 2023; 557:111315. [PMID: 36332666 DOI: 10.1016/j.jtbi.2022.111315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 09/24/2022] [Accepted: 10/10/2022] [Indexed: 11/07/2022]
Abstract
Several creatures can climb on smooth surfaces with the help of hairy adhesive pads on their legs. A rapid change from strong attachment to effortless detachment of the leg is enabled by the asymmetric geometry of the tarsal hairs. In this study, we propose mechanisms by which the hairy pad can be easily detached, even when the hairs possess no asymmetry. Here, we examine the possible function of the tibia-tarsus leg joint and the claws. Based on a spring-based model, we consider three modes of detachment: vertically pulling the pad while maintaining either a (1) fixed or a (2) free joint, or by (3) flexing the pad about the claw. We show that in all cases, the adhesion force can be significantly reduced due to elastic forces when the hairs deform non-uniformly across the array. Our proposed model illustrates the design advantage of such fibrillar adhesive systems, that not only provide strong adhesion, but also allow easy detachment, making them suitable as organs for fast locomotion and reliable hold. The presented approaches can be potentially used to switch the adhesion state in bio-inspired fibrillar adhesives, by incorporating artificial joints and claws into their design, without the need of asymmetric or stimuli-responsive fibrillar structures.
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Affiliation(s)
- Pranav Sudersan
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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15
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Gecko-Inspired Adhesive Mechanisms and Adhesives for Robots—A Review. ROBOTICS 2022. [DOI: 10.3390/robotics11060143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Small living organisms such as lizards possess naturally built functional surface textures that enable them to walk or climb on versatile surface topographies. Bio-mimicking the surface characteristics of these geckos has enormous potential to improve the accessibility of modern robotics. Therefore, gecko-inspired adhesives have significant industrial applications, including robotic endoscopy, bio-medical cleaning, medical bandage tapes, rock climbing adhesives, tissue adhesives, etc. As a result, synthetic adhesives have been developed by researchers, in addition to dry fibrillary adhesives, elastomeric adhesives, electrostatic adhesives, and thermoplastic adhesives. All these adhesives represent significant contributions towards robotic grippers and gloves, depending on the nature of the application. However, these adhesives often exhibit limitations in the form of fouling, wear, and tear, which restrict their functionalities and load-carrying capabilities in the natural environment. Therefore, it is essential to summarize the state of the art attributes of contemporary studies to extend the ongoing work in this field. This review summarizes different adhesion mechanisms involving gecko-inspired adhesives and attempts to explain the parameters and limitations which have impacts on adhesion. Additionally, different novel adhesive fabrication techniques such as replica molding, 3D direct laser writing, dip transfer processing, fused deposition modeling, and digital light processing are encapsulated.
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16
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An H, Jia N, Wang S, Peng Z, Chen S. Enhanced self-cleaning performance of bio-inspired micropillar-arrayed surface by shear. BIOINSPIRATION & BIOMIMETICS 2022; 17:066005. [PMID: 35931044 DOI: 10.1088/1748-3190/ac877b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 08/05/2022] [Indexed: 06/15/2023]
Abstract
Inspired by the sliding behavior of gecko feet during climbing, the contribution of the shear effect to the self-cleaning performance of a bio-inspired micropillar-arrayed surface is studied through a load-shear-pull contact process. It is found that self-cleaning efficiency can be enhanced significantly by shear. The efficiency also depends on microparticle size. For the case of relatively large and small microparticles, self-cleaning efficiency increases first and then almost keeps a constant with the increase of shear distance at different preloads. For medium microparticles, shear can effectively improve self-cleaning efficiency only when the preload is small. The mechanical mechanism under such enhancement is mainly due to the varying contact states between microparticles and micropillars with the shear distance. When the shear distance is large enough, the final self-cleaning efficiency is not sensitive to shear distance anymore because the contact state reaches dynamic equilibrium. Based on such a self-cleaning mechanism of large microparticles, a simple and effective manipulator that can efficiently transfer solid particles is further proposed.
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Affiliation(s)
- Huazhen An
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Beijing Key Laboratory of Lightweight Multi-Functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Ning Jia
- Department of Applied Mechanics, University of Science and Technology Beijing, Beijing 100083, People's Republic of China
| | - Shuai Wang
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029,People's Republic of China
| | - Zhilong Peng
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Beijing Key Laboratory of Lightweight Multi-Functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Shaohua Chen
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Beijing Key Laboratory of Lightweight Multi-Functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, People's Republic of China
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17
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Kim S, Liu N, Shestopalov AA. Contact Printing of Multilayered Thin Films with Shape Memory Polymers. ACS NANO 2022; 16:6134-6144. [PMID: 35353499 PMCID: PMC9047662 DOI: 10.1021/acsnano.1c11607] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 03/28/2022] [Indexed: 06/14/2023]
Abstract
This study describes a method for transfer printing microarrays of multilayered organic-inorganic thin films using shape memory printing stamps and microstructured donor substrates. By applying the films on the microstructured donor substrates during physical vapor deposition and modulating the interfacial adhesion using a shape memory elastomer during printing, this method achieves (1) high lateral and feature-edge resolution and (2) high transfer efficiency from the donor to the receiver substrate. For demonstration, polyurethane-acrylate stamps and silicon/silicon oxide donor substrates were used in the large-area transfer printing of organic-inorganic thin-film stacks with micrometer lateral dimensions and sub-200 nm thickness.
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18
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Wang Y, Hensel R, Arzt E. Attachment of bioinspired microfibrils in fluids: transition from a hydrodynamic to hydrostatic mechanism. J R Soc Interface 2022; 19:20220050. [PMID: 35382580 PMCID: PMC8984370 DOI: 10.1098/rsif.2022.0050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/10/2022] [Indexed: 11/12/2022] Open
Abstract
Reversible and switchable adhesion of elastomeric microstructures has attracted significant interest in the development of grippers for object manipulation. Their applications, however, have often been limited to dry conditions and adhesion of such deformable microfibrils in the fluid environment is less understood. In the present study, we performed adhesion tests in silicone oil using single cylindrical microfibrils of a flat-punch shape with a radius of 80 µm. Stiff fibrils were created using three-dimensional printing of an elastomeric resin with an elastic modulus of 500 MPa, and soft fibrils, with a modulus of 3.3 MPa, were moulded in polyurethane. Our results suggest that adhesion is dominated by hydrodynamic forces, which can be maximized by stiff materials and high retraction velocities, in line with theoretical predictions. The maximum pull-off stress of stiff cylindrical fibrils is 0.6 MPa, limited by cavitation and viscous fingering, occurring at retraction velocities greater than 2 µm s-1. Next, we add a mushroom cap to the microfibrils, which, in the case of the softer material, deforms upon retraction and leads to a transition to a hydrostatic suction regime with higher pull-off stresses ranging from 0.7 to 0.9 MPa. The effects of elastic modulus, fibril size and viscosity for underwater applications are illustrated in a mechanism map to provide guidance for design optimization.
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Affiliation(s)
- Yue Wang
- INM – Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - René Hensel
- INM – Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - Eduard Arzt
- INM – Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
- Department of Materials Science and Engineering, Saarland University, Campus D2 2, 66123 Saarbrücken, Germany
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19
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Blelloch ND, Yarbrough HJ, Mirica KA. Stimuli-responsive temporary adhesives: enabling debonding on demand through strategic molecular design. Chem Sci 2021; 12:15183-15205. [PMID: 34976340 PMCID: PMC8635214 DOI: 10.1039/d1sc03426j] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 10/07/2021] [Indexed: 11/24/2022] Open
Abstract
Stimuli-responsive temporary adhesives constitute a rapidly developing class of materials defined by the modulation of adhesion upon exposure to an external stimulus or stimuli. Engineering these materials to shift between two characteristic properties, strong adhesion and facile debonding, can be achieved through design strategies that target molecular functionalities. This perspective reviews the recent design and development of these materials, with a focus on the different stimuli that may initiate debonding. These stimuli include UV light, thermal energy, chemical triggers, and other potential triggers, such as mechanical force, sublimation, electromagnetism. The conclusion discusses the fundamental value of systematic investigations of the structure-property relationships within these materials and opportunities for unlocking novel functionalities in future versions of adhesives.
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Affiliation(s)
- Nicholas D Blelloch
- Burke Laboratory, Department of Chemistry, Dartmouth College Hanover New Hampshire 03755 USA http://www.miricagroup.com
| | - Hana J Yarbrough
- Burke Laboratory, Department of Chemistry, Dartmouth College Hanover New Hampshire 03755 USA http://www.miricagroup.com
| | - Katherine A Mirica
- Burke Laboratory, Department of Chemistry, Dartmouth College Hanover New Hampshire 03755 USA http://www.miricagroup.com
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20
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Dayan CB, Chun S, Krishna-Subbaiah N, Drotlef DM, Akolpoglu MB, Sitti M. 3D Printing of Elastomeric Bioinspired Complex Adhesive Microstructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2103826. [PMID: 34396591 DOI: 10.1002/adma.202103826] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/16/2021] [Indexed: 06/13/2023]
Abstract
Bioinspired elastomeric structural adhesives can provide reversible and controllable adhesion on dry/wet and synthetic/biological surfaces for a broad range of commercial applications. Shape complexity and performance of the existing structural adhesives are limited by the used specific fabrication technique, such as molding. To overcome these limitations by proposing complex 3D microstructured adhesive designs, a 3D elastomeric microstructure fabrication approach is implemented using two-photon-polymerization-based 3D printing. A custom aliphatic urethane-acrylate-based elastomer is used as the 3D printing material. Two designs are demonstrated with two combined biological inspirations to show the advanced capabilities enabled by the proposed fabrication approach and custom elastomer. The first design focuses on springtail- and gecko-inspired hybrid microfiber adhesive, which has the multifunctionalities of side-surface liquid super-repellency, top-surface liquid super-repellency, and strong reversible adhesion features in a single fiber array. The second design primarily centers on octopus- and gecko-inspired hybrid adhesive, which exhibits the benefits of both octopus- and gecko-inspired microstructured adhesives for strong reversible adhesion on both wet and dry surfaces, such as skin. This fabrication approach could be used to produce many other 3D complex elastomeric structural adhesives for future real-world applications.
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Affiliation(s)
- Cem Balda Dayan
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Sungwoo Chun
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
- Department of Electronics and Information Engineering, Korea University, Sejong, 30019, Republic of Korea
| | - Nagaraj Krishna-Subbaiah
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Dirk-Michael Drotlef
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Mukrime Birgul Akolpoglu
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Metin Sitti
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
- Institute for Biomedical Engineering, ETH Zürich, Zürich, 8092, Switzerland
- School of Medicine and College of Engineering, Koç University, Istanbul, 34450, Turkey
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21
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Son D, Liimatainen V, Sitti M. Machine Learning-Based and Experimentally Validated Optimal Adhesive Fibril Designs. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2102867. [PMID: 34414656 DOI: 10.1002/smll.202102867] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Indexed: 06/13/2023]
Abstract
Setae, fibrils located on a gecko's feet, have been an inspiration of synthetic dry microfibrillar adhesives in the last two decades for a wide range of applications due to unique properties: residue-free, repeatable, tunable, controllable and silent adhesion; self-cleaning; and breathability. However, designing dry fibrillar adhesives is limited by a template-based-design-approach using a pre-determined bioinspired T- or wedge-shaped mushroom tip. Here, a machine learning-based computational approach to optimize designs of adhesive fibrils is shown, exploring a much broader design space. A combination of Bayesian optimization and finite element methods creates novel optimal designs of adhesive fibrils, which are fabricated by two-photon-polymerization-based 3D microprinting and double-molding-based replication out of polydimethylsiloxane. Such optimal elastomeric fibril designs outperform previously proposed designs by maximum 77% in the experiments of dry adhesion performance on smooth surfaces. Furthermore, finite-element-analyses reveal that the adhesion of the fibrils is sensitive to the 3D fibril stem shape, tensile deformation, and fibril microfabrication limits, which contrast with the previous assumptions that mostly neglect the deformation of the fibril tip and stem, and focus only on the fibril tip geometry. The proposed computational fibril design could help design future optimal fibrils with less help from human intuition.
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Affiliation(s)
- Donghoon Son
- School of Mechanical Engineering, Pusan National University, Busan, 46241, South Korea
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Ville Liimatainen
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
- Okmetic Oy, Vantaa, 01510, Finland
| | - Metin Sitti
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
- Institute for Biomedical Engineering, ETH Zurich, Zurich, 8092, Switzerland
- School of Medicine and College of Engineering, Koç University, Istanbul, 34450, Turkey
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22
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Li S, Liu H, Tian H, Wang C, Wang D, Wu Y, Shao J. Dytiscus lapponicus-Inspired Structure with High Adhesion in Dry and Underwater Environments. ACS APPLIED MATERIALS & INTERFACES 2021; 13:42287-42296. [PMID: 34455771 DOI: 10.1021/acsami.1c13604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The epidermal adhesive structure of many animals generates reliable adhesion on their engaged surfaces. However, current bio-inspired adhesion structures are difficult to function well in dry and underwater environments simultaneously. Interestingly, the male Dytiscus lapponicus attaches firmly to the rough shell of the female D. lapponicus in both dry and underwater conditions owing to the adhesive setae of its forelegs, and to the best of our knowledge, designing adhesive structures on multienvironments has never been reported. Here, a D. lapponicus-inspired adhesion structure (DIAS) is proposed and fabricated using double-exposure-fill molding technology accompanied with the material curing shrinkage, in which different structural features could be achieved by varying curing shrinkage ratios, elastic moduli, and back exposure time. The DIAS offered high, reversible, and repeatable strength in dry and underwater conditions with values of 205 and 133 kPa, respectively. By comparing the adhesion properties of different shapes via testing experiments and numerical analysis, a structural feature with an inclination of 15° was found to be optimal. Finally, the potential application of the DIAS in flexible electronic smart skin-attachable devices was demonstrated on a pig skin, paving the way for further bio-inspired adhesive designs for both dry and wet scenarios.
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Affiliation(s)
- Shuai Li
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Haoran Liu
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Hongmiao Tian
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Chunhui Wang
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Duorui Wang
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Yihang Wu
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Jinyou Shao
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
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23
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An H, Wang S, Li D, Peng Z, Chen S. Self-Cleaning Performance of the Micropillar-Arrayed Surface and Its Micro-Scale Mechanical Mechanism. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10079-10088. [PMID: 34375529 DOI: 10.1021/acs.langmuir.1c01398] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The exceptional adhesive ability of geckos remains almost uninfluenced by contaminated surfaces, showing that the adhesion system of geckos has self-cleaning properties. Although there have been several studies on the self-cleaning performance of geckos and gecko-inspired synthetic adhesives, the microscale mechanical mechanism of self-cleaning is still unclear. In the present study, a micropillar-arrayed surface is fabricated using a template molding method to investigate its self-cleaning performance in a load-pull contact process. The effects of preload, microparticle size on self-cleaning properties are studied. The self-cleaning efficiency of the micropillar-arrayed surface is found to increase with an increase in the microparticle size. For large and small microparticles, self-cleaning efficiency increases with an increase in the preload. For medium microparticles, self-cleaning efficiency first increases and then decreases as the preload increases. The mechanical mechanism underlying such self-cleaning performance is further elucidated; it is mainly attributed to the competition among the elastic energy stored in the micropillars induced by the bending deformation, the interfacial adhesion energy between the microparticles and the deformed micropillars, and the interfacial adhesion energy between the microparticles and substrate, as well as the varying contact states between the microparticles and the deformed micropillars. The preload can not only change the contact states between the microparticles and the micropillar-arrayed surface but also influence the bending elastic energy stored in the micropillars. The results obtained in the present study can help deeply understand the self-cleaning mechanism of micropillar-arrayed surfaces as well as provide a guideline for designing functional surfaces with high self-cleaning efficiency.
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Affiliation(s)
- Huazhen An
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, China
- Beijing Key Laboratory of Lightweight Multi-functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, China
| | - Shuai Wang
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Dawei Li
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, China
- Beijing Key Laboratory of Lightweight Multi-functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, China
| | - Zhilong Peng
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, China
- Beijing Key Laboratory of Lightweight Multi-functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, China
| | - Shaohua Chen
- Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, China
- Beijing Key Laboratory of Lightweight Multi-functional Composite Materials and Structures, Beijing Institute of Technology, Beijing 100081, China
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24
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Lazarus BS, Chadha C, Velasco-Hogan A, Barbosa JD, Jasiuk I, Meyers MA. Engineering with keratin: A functional material and a source of bioinspiration. iScience 2021; 24:102798. [PMID: 34355149 PMCID: PMC8319812 DOI: 10.1016/j.isci.2021.102798] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Keratin is a highly multifunctional biopolymer serving various roles in nature due to its diverse material properties, wide spectrum of structural designs, and impressive performance. Keratin-based materials are mechanically robust, thermally insulating, lightweight, capable of undergoing reversible adhesion through van der Waals forces, and exhibit structural coloration and hydrophobic surfaces. Thus, they have become templates for bioinspired designs and have even been applied as a functional material for biomedical applications and environmentally sustainable fiber-reinforced composites. This review aims to highlight keratin's remarkable capabilities as a biological component, a source of design inspiration, and an engineering material. We conclude with future directions for the exploration of keratinous materials.
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Affiliation(s)
- Benjamin S. Lazarus
- Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
| | - Charul Chadha
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - Audrey Velasco-Hogan
- Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
| | | | - Iwona Jasiuk
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - Marc A. Meyers
- Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
- Department of Mechanical and Aerospace Engineering, University of California San Diego, San Diego, CA, USA
- Department of Nanoengineering, University of California San Diego, San Diego, CA, USA
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25
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Adhesive performance enhancement of the mushroom-shaped microstructured elastomer by atmospheric plasma treatment. Biointerphases 2021; 16:041004. [PMID: 34301148 DOI: 10.1116/6.0000999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Bioinspired reversible adhesives that have been developed in the course of recent years have found several applications in robotics, transportation, and marine applications. One of their prominent features is strong reversible static adhesion. To fulfill the requirements of various applications, the static adhesive performance of these materials can be enhanced by modifying the material and surface properties. In this work, the mushroom-shaped adhesive microstructured surface was functionalized by atmospheric plasma treatment to enhance its adhesive performances. Through optimizing the duration of the treatment, the pull-off force increase of up to 60% can be reached after the treatment in comparison to the measurements performed on the same mushroom-shaped microstructured sample before the treatment. In comparison to the microstructured samples, the attachment of the unstructured sample made of the same silicone elastomer was enhanced by 16% after plasma treatment. The strong adhesion enhancement on the microstructured sample was attributed to the combination of the changed effective elastic modulus of the material and the specific detachment behavior of microstructures. These results are anticipated to contribute to the further development of bioinspired dry adhesives and may potentially widen their usage in various technological applications.
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Zhou T, Ruan B, Che J, Li H, Chen X, Jiang Z. Gecko-Inspired Biomimetic Surfaces with Annular Wedge Structures Fabricated by Ultraprecision Machining and Replica Molding. ACS OMEGA 2021; 6:6757-6765. [PMID: 33748589 PMCID: PMC7970495 DOI: 10.1021/acsomega.0c05804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/23/2021] [Indexed: 06/12/2023]
Abstract
The current research on gecko-inspired dry adhesives is focused on micropillar arrays with different terminal shapes, such as flat, spherical, mushroom, and spatula tips. The corresponding processing methods are mostly chemical methods, including lithography, etching, and deposition, which not only are complex, expensive, and environmentally unfriendly, but also cannot completely ensure microstructural integrity or performance stability. The present study demonstrates a high-precision, high-efficiency, and green method for the fabrication of a gecko-inspired surface, which can promote its application in dexterous robot hands and mechanical grippers. Based on the bendable lamellar structures of the gecko, annular wedge adhesive surfaces that stick to the finger surfaces of dexterous robot hands to improve their load capacity are proposed and fabricated via a suitable combined processing method of ultraprecision machining and replica molding. The greater the width, the higher the replication integrity, and when the minimum width is 20 μm, the replication error is less than 5.5% due to the superior processing performance of the nickel-phosphorus (Ni-P) plating of the master mold. The fabricated annular wedge structures with an optimized width of 20 μm not only exhibit a strong friction force of up to 35.48 mN under a preload of 20 mN in the GCr15/poly(dimethylsiloxane) (PDMS) friction pair but also demonstrate an obviously improved anisotropic friction characteristic of up to λ = 1.36, as the molecular force exhibits a stronger increase as compared to the decrease of the mechanical force of the structure with a small width.
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Affiliation(s)
- Tianfeng Zhou
- School
of Mechanical Engineering and School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Benshuai Ruan
- School
of Mechanical Engineering and School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Jiangtao Che
- School
of Mechanical Engineering and School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Hui Li
- School
of Mechanical Engineering and School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Xi Chen
- School
of Mechanical Engineering and School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Zhihong Jiang
- School
of Mechanical Engineering and School of Mechatronic Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
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He Z, Liu Z, Li M, Hui CY, Jagota A. Meso-scale dislocations and friction of shape-complementary soft interfaces. J R Soc Interface 2021; 18:20200940. [PMID: 33530861 DOI: 10.1098/rsif.2020.0940] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The interface between two surfaces patterned with complementary shapes such as arrays of ridge-channel structures or pillars accommodates relative misorientation and lattice mismatch by spontaneous production of dislocation arrays. Here, we show that the relative sliding of such an interface is accomplished by dislocation glide on the interfacial plane. An exception is the singular case where the lattices are perfectly matched across the sample dimension, in which case sliding is accompanied by motion of edge-nucleated defects. These are meso-scale analogues of molecular sliding friction mechanisms between crystalline interfaces. The dislocations, in addition to the long-range elastic energy associated with their Burgers vectors, also cause significant out-of-plane dilation, which props open the interface locally. For this reason, the sliding friction is strongly pressure dependent; it also depends on the relative orientation of the patterns. Sliding friction can be strongly enhanced compared with a control, showing that shape-complementary interfaces can be engineered for strongly enhanced pressure- and orientation-dependent frictional properties in soft solids.
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Affiliation(s)
- Zhenping He
- Department of Bioengineering, Lehigh University, Bethlehem, PA, USA
| | - Zezhou Liu
- Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA
| | - Meng Li
- Department of Bioengineering, Lehigh University, Bethlehem, PA, USA.,College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China
| | - Chung-Yuen Hui
- Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA
| | - Anand Jagota
- Department of Bioengineering, Lehigh University, Bethlehem, PA, USA.,Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, USA
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Kizilkan E, Strueben J, Staubitz A, Gorb SN. Bioinspired photocontrollable microstructured transport device. Sci Robot 2021; 2:2/2/eaak9454. [PMID: 33157866 DOI: 10.1126/scirobotics.aak9454] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Accepted: 12/15/2016] [Indexed: 11/02/2022]
Abstract
Geckos, which can walk upside down on vertical and underneath horizontal surfaces, owe this ability to the hierarchical structures under their toes. These structures are responsible for substantial adhesion and, at the same time, for quick detachment by mechanical stimulus through leg movements. Inspired by such stimuli-responsive systems in nature, we developed an artificial, photocontrollable microstructured transport device. Through tunable ultraviolet light illumination, the adhesive ability of this bioinspired transport device is reduced up to a factor of 2.7 in terms of adhesive forces and is quickly recovered when the light stimulus ceases. This bioinspired photocontrollable device has been used in a pick-up and drop-down system for transporting planar and three-dimensional solid objects.
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Affiliation(s)
- Emre Kizilkan
- Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, 24118 Kiel, Germany.
| | - Jan Strueben
- Otto Diels Institute for Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, 24118 Kiel, Germany.,Institute for Organic and Analytical Chemistry, University of Bremen, Leobener Straße NW 2 C, 28359 Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstraße 1, 28359 Bremen, Germany
| | - Anne Staubitz
- Otto Diels Institute for Organic Chemistry, Kiel University, Otto-Hahn-Platz 4, 24118 Kiel, Germany. .,Institute for Organic and Analytical Chemistry, University of Bremen, Leobener Straße NW 2 C, 28359 Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstraße 1, 28359 Bremen, Germany
| | - Stanislav N Gorb
- Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, 24118 Kiel, Germany.
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Liu Q, Tan D, Meng F, Yang B, Shi Z, Wang X, Li Q, Nie C, Liu S, Xue L. Adhesion Enhancement of Micropillar Array by Combining the Adhesive Design from Gecko and Tree Frog. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2005493. [PMID: 33369100 DOI: 10.1002/smll.202005493] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/13/2020] [Indexed: 06/12/2023]
Abstract
It has long been demonstrated the gecko-inspired micropillar array with T-shape tips possesses the best adhesion performance of a given material. The further enhancement of the adhesion performances of T-shape micropillars can offer redundant adhesion to compensate for the inevitable improper contacts. Here, the array of T-shape polydimethylsiloxane (PDMS) micropillars is incorporated with gradient dispersed calcium carbonate nanoparticles in the micropillar stalk, termed as T-shape gradient micropillars (TG), possessing the modulus gradient with stiff tip and soft root. The gradient modulus in TG facilitates the contact formation and regulates the stress at the detaching interface, resulting in a 4.6 times adhesion and 2.4 times friction as compared with the pure PDMS T-shape micropillar arrays. The study here provides a new design strategy for the super-strong structured dry adhesives.
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Affiliation(s)
- Quan Liu
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Di Tan
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Fandong Meng
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Baisong Yang
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Zhekun Shi
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Xin Wang
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Qian Li
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Chang Nie
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Sheng Liu
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
| | - Longjian Xue
- School of Power and Mechanical Engineering, The Institute of Technological Science, Wuhan University, South Donghu Road 8, Wuhan, 430072, China
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30
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Dong X, Zhao H, Li J, Tian Y, Zeng H, Ramos MA, Hu TS, Xu Q. Progress in Bioinspired Dry and Wet Gradient Materials from Design Principles to Engineering Applications. iScience 2020; 23:101749. [PMID: 33241197 PMCID: PMC7672307 DOI: 10.1016/j.isci.2020.101749] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Nature does nothing in vain. Through millions of years of revolution, living organisms have evolved hierarchical and anisotropic structures to maximize their survival in complex and dynamic environments. Many of these structures are intrinsically heterogeneous and often with functional gradient distributions. Understanding the convergent and divergent gradient designs in the natural material systems may lead to a new paradigm shift in the development of next-generation high-performance bio-/nano-materials and devices that are critically needed in energy, environmental remediation, and biomedical fields. Herein, we review the basic design principles and highlight some of the prominent examples of gradient biological materials/structures discovered over the past few decades. Interestingly, despite the anisotropic features in one direction (i.e., in terms of gradient compositions and properties), these natural structures retain certain levels of symmetry, including point symmetry, axial symmetry, mirror symmetry, and 3D symmetry. We further demonstrate the state-of-the-art fabrication techniques and procedures in making the biomimetic counterparts. Some prototypes showcase optimized properties surpassing those seen in the biological model systems. Finally, we summarize the latest applications of these synthetic functional gradient materials and structures in robotics, biomedical, energy, and environmental fields, along with their future perspectives. This review may stimulate scientists, engineers, and inventors to explore this emerging and disruptive research methodology and endeavors.
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Affiliation(s)
- Xiaoxiao Dong
- State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China
| | - Hong Zhao
- State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China
| | - Jiapeng Li
- State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China
| | - Yu Tian
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Melvin A Ramos
- Department of Mechanical Engineering, California State University, Los Angeles, CA 90032, USA
| | - Travis Shihao Hu
- Department of Mechanical Engineering, California State University, Los Angeles, CA 90032, USA
| | - Quan Xu
- State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China
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31
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Bowen LK, Johannes K, Zuetell E, Calahan KN, Edmundowicz SA, Long R, Rentschler ME. Patterned enteroscopy balloon design factors influence tissue anchoring. J Mech Behav Biomed Mater 2020; 111:103966. [PMID: 32810654 DOI: 10.1016/j.jmbbm.2020.103966] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/27/2020] [Accepted: 06/30/2020] [Indexed: 12/22/2022]
Abstract
Balloon-assisted enteroscopy procedures allow visualization and intervention in the small intestine. These balloons anchor an endoscope and/or overtube to the small intestine, allowing endoscopists to plicate the small intestine over the overtube. This procedure can extend examination deeper into the small intestine than the length of the endoscope would allow with direct examination. However, procedures are often prolonged or incomplete due to balloon slippage. Enteroscopy balloons are pressure-limited to ensure patient safety and thus, improving anchoring without increasing pressure is essential. Patterning balloon exteriors with discrete features may enhance anchoring at the tissue-balloon interface. Here, the pattern design space is explored to determine factors that influence tissue anchoring. The anchoring ability of smooth versus balloons with patterned features is investigated by experimentally measuring a peak force required to induce slippage of an inflated balloon inside ex-vivo porcine small intestine. Stiffer materials, low aspect-ratio features, and pattern area/location on the balloons significantly increase peak force compared to smooth silicone balloons. Smooth latex balloons, used for standard enteroscopy, have the lowest peak force. This work demonstrates both a method to pattern curved surfaces and that a balloon with patterned features improves anchoring against a deformable, lubricated tissue interface.
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Affiliation(s)
- Leah K Bowen
- Department of Mechanical Engineering, ECME 114, 1111 Engineering Drive, University of Colorado Boulder, Boulder, CO, 80309, USA; Medical Scientist Training Program, 12631 E. 17th Avenue, AO1 Room 2601, Mail Stop B176, University of Colorado, Anschutz Medical Campus, Aurora, CO, 80045, USA.
| | - Karl Johannes
- Department of Mechanical Engineering, ECME 114, 1111 Engineering Drive, University of Colorado Boulder, Boulder, CO, 80309, USA.
| | - Emily Zuetell
- Department of Mechanical Engineering, ECME 114, 1111 Engineering Drive, University of Colorado Boulder, Boulder, CO, 80309, USA.
| | - Kristin N Calahan
- Department of Mechanical Engineering, ECME 114, 1111 Engineering Drive, University of Colorado Boulder, Boulder, CO, 80309, USA; BioFrontiers Institute, University of Colorado Boulder, UCB 596, Boulder, CO, 80309, USA.
| | - Steven A Edmundowicz
- Department of Medicine, Gastroenterology, University of Colorado, Anschutz Medical Campus, 12631 E. 17th Ave. B158, Aurora, CO, 80045, USA.
| | - Rong Long
- Department of Mechanical Engineering, ECME 114, 1111 Engineering Drive, University of Colorado Boulder, Boulder, CO, 80309, USA.
| | - Mark E Rentschler
- Department of Mechanical Engineering, ECME 114, 1111 Engineering Drive, University of Colorado Boulder, Boulder, CO, 80309, USA; Department of Surgery, University of Colorado Anschutz Medical Campus, 12631 E 17th Ave #6117, Aurora, CO, 80045, USA.
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32
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Geikowsky E, Aksak B. Bioinspired fibrillar adhesives with shape-controlled off-center caps for switchable and directional adhesion. BIOINSPIRATION & BIOMIMETICS 2020; 15:056007. [PMID: 32697767 DOI: 10.1088/1748-3190/ab98dd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Most natural fibrillar adhesive structures feature spatula-shaped caps as a common adhesive element. The spatula-shaped tips endow adhesive fiber arrays with on demand adhesion, allowing them to maximize adhesion in a given direction and facilitate effortless detachment. Replication of off-center spatula ends synthetically, a key contributor to directional adhesion, remains a fabrication challenge. In this work, a method to feature synthetic microfiber adhesives with off-center caps is proposed. This new method decouples the shape and placement dependency between the cap and the stem, providing endless possibilities in positioning of the tip with respect to the stem and the two-dimensional shape and the material of both the cap and the stem. Experiments of directional adhesion were carried out to demonstrate switchable adhesion relevant for pick & place type applications, and the ability to generate high friction and easy removal. Fibers with off-center caps were shown to promote easy detachment after strong adhesion in both straight and bent stalks. Straight fibers with off-center caps showed 3-to-5-fold reduction in adhesion when pulled diagonally instead of vertically from the adhering surface. Bent fibers on the other hand provided up to 3 times more maximum shear than adhesion, when fibers are dragged laterally against the cap overhang. These results show the versatility and the potential of the proposed fabrication method in designing application specific directional and switchable adhesives.
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Affiliation(s)
- E Geikowsky
- Mechanical Engineering, Texas Tech University, Lubbock, TX 79409-1021, United States of America. Departamento de Ingeniería Metalúrgica y de Materiales, Universidad Técnica Federico Santa María, Valparaíso, Chile
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Mohammadi Nasab A, Luo A, Sharifi S, Turner KT, Shan W. Switchable Adhesion via Subsurface Pressure Modulation. ACS APPLIED MATERIALS & INTERFACES 2020; 12:27717-27725. [PMID: 32449361 DOI: 10.1021/acsami.0c05367] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Materials and devices with tunable dry adhesion have many applications, including transfer printing, climbing robots, and gripping in pick-and-place processes. In this paper, a novel soft device to achieve dynamically tunable dry adhesion via modulation of subsurface pneumatic pressure is introduced. Specifically, a cylindrical elastomer pillar with a mushroom-shaped cap and annular chamber that can be pressurized to tune the adhesion is investigated. Finite element-based mechanics models and experiments are used to design, understand, and demonstrate the adhesion of the device. Specifically, the device is designed using mechanics modeling such that the pressure applied inside the annular chamber significantly alters the stress distribution at the adhered interface and thus changes the effective adhesion strength. Devices made of polydimethylsiloxane (PDMS) with different elastic moduli were tested against glass, silicon, and aluminum substrates. Adhesion strengths (σ0) ranging from ∼37 kPa (between PDMS and glass) to ∼67 kPa (between PDMS and polished aluminum) are achieved for the nonpressurized state. For all cases, regardless of the material and roughness of the substrates, the adhesion strength dropped to 40% of the strength of the nonpressurized state (equivalent to a 2.5× adhesion switching ratio) by increasing the chamber pressure from 0.3σ0 to 0.6σ0. Furthermore, the strength drops to 20% of the unpressurized strength (equivalent to a 5× adhesion switching ratio) when the chamber pressure is increased to σ0.
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Affiliation(s)
- Amir Mohammadi Nasab
- Mechanical Engineering Department, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States
| | - Aoyi Luo
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, United States
| | - Siavash Sharifi
- Mechanical Engineering Department, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States
- Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, New York 13244, United States
| | - Kevin T Turner
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, United States
| | - Wanliang Shan
- Mechanical Engineering Department, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States
- Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, New York 13244, United States
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Kim Y, Yang C, Kim Y, Gu GX, Ryu S. Designing an Adhesive Pillar Shape with Deep Learning-Based Optimization. ACS APPLIED MATERIALS & INTERFACES 2020; 12:24458-24465. [PMID: 32374994 DOI: 10.1021/acsami.0c04123] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Over the past decades, significant effort has been made to improve the adhesive properties of adhesive pillars, by searching for pillar shapes with optimized interfacial stress distribution. However, the shape optimizations in the previous studies are conducted by considering specific pillar forms with a few parameters, hence with limited design space. In this study, we present a framework to find a free-form optimized adhesive pillar shape out of extensive design space. We generate 200 000 different shapes of adhesive pillars based on the Bézier curve with a few control points by considering two distinct edge shapes, sharp and truncated edges, to account for the limitation in the realistic manufacturing resolution. The resulting interfacial stress distributions from numerical simulations are used to train deep neural networks for each edge type. Our deep learning model shows greater than 99% classification accuracy on a limited data set with orders of magnitude speedup in computation time compared to finite element analyses. On the basis of the trained neural network, we conduct genetic optimization by maximizing a fitness function that prefers the uniform interfacial stress distribution with neither stress peak nor singularity. The optimized adhesive pillar shape is composed of smoothly mixed convex and concave parts and shows improved uniformity in the interfacial stress distribution. Our study also demonstrates that the deep learning can be used for nonparametric curve optimization task with diverse fitness function.
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Affiliation(s)
- Yongtae Kim
- Department of Mechanical Engineering & KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Charles Yang
- Department of Mechanical Engineering, University of California, Berkeley, California 94720, United States
| | - Youngsoo Kim
- Department of Mechanical Engineering & KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Grace X Gu
- Department of Mechanical Engineering, University of California, Berkeley, California 94720, United States
| | - Seunghwa Ryu
- Department of Mechanical Engineering & KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
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Liimatainen V, Drotlef DM, Son D, Sitti M. Liquid-Superrepellent Bioinspired Fibrillar Adhesives. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2000497. [PMID: 32239584 DOI: 10.1002/adma.202000497] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/20/2020] [Accepted: 03/09/2020] [Indexed: 06/11/2023]
Abstract
Bioinspired elastomeric fibrillar surfaces have significant potential as reversible dry adhesives, but their adhesion performance is sensitive to the presence of liquids at the contact interface. Like their models in nature, many artificial mimics can effectively repel water, but fail when low-surface-tension liquids are introduced at the contact interface. A bioinspired fibrillar adhesive surface that is liquid-superrepellent even toward ultralow-surface-tension liquids while retaining its adhesive properties is proposed herein. This surface combines the effective adhesion principle of mushroom-shaped fibrillar arrays with liquid repellency based on double re-entrant fibril tip geometry. The adhesion performance of the proposed microfibril structures is retained even when low-surface-tension liquids are added to the contact interface. The extreme liquid repellency enables real-world applications of fibrillar adhesives for surfaces covered with water, oil, and other liquids. Moreover, fully elastomeric liquid-superrepellent surfaces are mechanically not brittle, highly robust against physical contact, and highly deformable and stretchable, which can increase the real-world uses of such antiwetting surfaces.
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Affiliation(s)
- Ville Liimatainen
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
| | - Dirk-Michael Drotlef
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
| | - Donghoon Son
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
| | - Metin Sitti
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
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Abstract
SummaryThis paper describes the development of a gecko-inspired robotic gripper for grasping flat objects using Scott–Russell mechanisms. Compared to previously reported grippers that utilize gecko-like adhesives, the one presented here produces higher normal adhesion and has robustness and controllability advantages. To verify the applicability of proposed gripper, a mechanical model and experimental results on a variety of substrates are presented. The experimental results demonstrated a 19.6% and 50% increase in normal adhesion using a preload of <15 and <30 N, respectively, compared to previously reported results under similar testing parameters and conditions.
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37
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Stark AY, Mitchell CT. Stick or Slip: Adhesive Performance of Geckos and Gecko-Inspired Synthetics in Wet Environments. Integr Comp Biol 2019; 59:214-226. [PMID: 30873552 DOI: 10.1093/icb/icz008] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The gecko adhesive system has inspired hundreds of synthetic mimics principally focused on replicating the strong, reversible, and versatile properties of the natural system. For geckos native to the tropics, versatility includes the need to remain attached to substrates that become wet from high humidity and frequent rain. Paradoxically, van der Waals forces, the principal mechanism responsible for gecko adhesion, reduce to zero when two contacting surfaces separate even slightly by entrapped water layers. A series of laboratory studies show that instead of slipping, geckos maintain and even improve their adhesive performance in many wet conditions (i.e., on wet hydrophobic substrates, on humid substrates held at low temperatures). The mechanism for this is not fully clarified, and likely ranges in scale from the chemical and material properties of the gecko's contact structures called setae (e.g., setae soften and change surface confirmation when exposed to water), to their locomotor biomechanics and decision-making behavior when encountering water on a substrate in their natural environment (e.g., some geckos tend to run faster and stop more frequently on misted substrates than dry). Current work has also focused on applying results from the natural system to gecko-inspired synthetic adhesives, improving their performance in wet conditions. Gecko-inspired synthetic adhesives have also provided a unique opportunity to test hypotheses about the natural system in semi-natural conditions replicated in the laboratory. Despite many detailed studies focused on the role of water and humidity on gecko and gecko-inspired synthetic adhesion, there remains several outstanding questions: (1) what, if any, role does capillary or capillary-like adhesion play on overall adhesive performance of geckos and gecko-inspired synthetics, (2) how do chemical and material changes at the surface and in the bulk of gecko setae and synthetic fibrils change when exposed to water, and what does this mean for adhesive performance, and (3) how much water do geckos encounter in their native environment, and what is their corresponding behavioral response? This review will detail what we know about gecko adhesion in wet environments, and outline the necessary next steps in biological and synthetic system investigations.
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Affiliation(s)
- Alyssa Y Stark
- Department of Biology, Villanova University, 800 East Lancaster Avenue, Villanova, PA 19085, USA
| | - Christopher T Mitchell
- Department of Biology, Villanova University, 800 East Lancaster Avenue, Villanova, PA 19085, USA
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Drotlef DM, Dayan CB, Sitti M. Bio-inspired Composite Microfibers for Strong and Reversible Adhesion on Smooth Surfaces. Integr Comp Biol 2019; 59:227-235. [PMID: 30895297 PMCID: PMC6650614 DOI: 10.1093/icb/icz009] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A novel approach for high-performance gecko-inspired adhesives for strong and reversible adhesion to smooth surfaces is proposed. The composite patterns comprising elastomeric mushroom-shaped microfibers decorated with an extremely soft and thin terminal layer of pressure sensitive adhesive. Through the optimal tip shape and improved load sharing, the adhesion performance was greatly enhanced. A high adhesion strength of 300 kPa together with superior durability on smooth surfaces are achieved, outperforming monolithic fibers by 35 times. Our concept of composite microfibrillar adhesives provides significant benefits for real world applications including wearable medical devices, transfer printing systems, and robotic manipulation.
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Affiliation(s)
- D-M Drotlef
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart 70569, Germany
| | - C B Dayan
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart 70569, Germany
| | - M Sitti
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart 70569, Germany
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Li B, Kappl M, Han L, Cui J, Zhou F, Del Campo A. Goosebumps-Inspired Microgel Patterns with Switchable Adhesion and Friction. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1902376. [PMID: 31310426 DOI: 10.1002/smll.201902376] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 06/21/2019] [Indexed: 05/18/2023]
Abstract
A substrate mimicking the surface topography and temperature sensitivity of skin goosebumps is fabricated. Close-packed arrays of thermoresponsive microgel particles undergo topographical changes in response to temperature changes between 25 and 37 °C, resembling the goosebump structure that human skin develops in response to temperature changes or other circumstances. Specifically, positively charged poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes serve as an anchoring substrate for negatively charged poly(NIPAm-co-AA) microgels. The packing density and particle morphology can be tuned by brush layer thickness and pH of the microgel suspension. For brush layer thickness below 50 nm, particle monolayers are observed, with slightly flattened particle morphology at pH 3 and highly collapsed particles at pH above 7. Polymer brush films with thickness above 50 nm lead to the formation of particle multilayers. The temperature responsiveness of the monolayer assemblies allows reversible changes in the film morphology, which in turn affects underwater adhesion and friction at 25 and 37 °C. These results are promising for the design of new functional materials and may also serve as a model for biological structures and processes.
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Affiliation(s)
- Bin Li
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123, Saarbrücken, Germany
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Lu Han
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123, Saarbrücken, Germany
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, 610054, Chengdu, China
| | - Jiaxi Cui
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123, Saarbrücken, Germany
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, 610054, Chengdu, China
| | - Feng Zhou
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 730000, Lanzhou, China
| | - Aránzazu Del Campo
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123, Saarbrücken, Germany
- Chemistry Department, Saarland University, 66123, Saarbrücken, Germany
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40
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Meng F, Liu Q, Wang X, Tan D, Xue L, Barnes WJP. Tree frog adhesion biomimetics: opportunities for the development of new, smart adhesives that adhere under wet conditions. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20190131. [PMID: 31177956 PMCID: PMC6562351 DOI: 10.1098/rsta.2019.0131] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 04/05/2019] [Indexed: 05/31/2023]
Abstract
Enlarged adhesive toe pads on the tip of each digit allow tree frogs to climb smooth vertical and overhanging surfaces, and are effective in generating reversible adhesion under both dry and wet conditions. In this review, we discuss the complexities of the structure of tree frog toe pads in relation to their function and review their biomimetic potential. Of particular importance are the (largely) hexagonal epithelial cells surrounded by deep channels that cover the surface of each toe pad and the array of nanopillars on their surface. Fluid secreted by the pads covers the surface of each pad, so the pads adhere by wet adhesion, involving both capillarity and viscosity-dependent forces. The fabrication and testing of toe pad mimics are challenging, but valuable both for testing hypotheses concerning tree frog toe pad function and for developing toe pad mimics. Initial mimics involved the fabrication of hexagonal pillars mimicking the toe pad epithelial structure. More recent ones additionally replicate the nanostructures on their surface. Finally we describe some of the biomimetic applications that have been developed from toe pad mimics, which include both bioinspired adhesives and friction-generating devices. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.
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Affiliation(s)
- Fandong Meng
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan, People's Republic of China
| | - Quan Liu
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan, People's Republic of China
| | - Xin Wang
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan, People's Republic of China
| | - Di Tan
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan, People's Republic of China
| | - Longjian Xue
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan, People's Republic of China
| | - W. Jon. P. Barnes
- Centre for Cell Engineering, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, UK
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41
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Booth JA, Tinnemann V, Hensel R, Arzt E, McMeeking RM, Foster KL. Statistical properties of defect-dependent detachment strength in bioinspired dry adhesives. J R Soc Interface 2019; 16:20190239. [PMID: 31362613 DOI: 10.1098/rsif.2019.0239] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dry adhesives using surface microstructures inspired by climbing animals have been recognized for their potentially novel capabilities, with relevance to a range of applications including pick-and-place handling. Past work has suggested that performance may be strongly dependent on variability in the critical defect size among fibrillar sub-contacts. However, it has not been directly verified that the resulting adhesive strength distribution is well described by the statistical theory of fracture used. Using in situ contact visualization, we characterize adhesive strength on a fibril-by-fibril basis for a synthetic fibrillar adhesive. Two distinct detachment mechanisms are observed. The fundamental, design-dependent mechanism involves defect propagation from within the contact. The secondary mechanism involves defect propagation from fabrication imperfections at the perimeter. The existence of two defect populations complicates characterization of the statistical properties. This is addressed by using the mean order ranking method to isolate the fundamental mechanism. The statistical properties obtained are subsequently used within a bimodal framework, allowing description of the secondary mechanism. Implications for performance are discussed, including the improvement of strength associated with elimination of fabrication imperfections. This statistical analysis of defect-dependent detachment represents a more complete approach to the characterization of fibrillar adhesives, offering new insight for design and fabrication.
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Affiliation(s)
- Jamie A Booth
- Mechanical Engineering Department, University of California, Santa Barbara, CA 93106, USA
| | - Verena Tinnemann
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - René Hensel
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - Eduard Arzt
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.,Department of Materials Science and Engineering, Saarland University, Saarbrücken, Germany
| | - Robert M McMeeking
- Mechanical Engineering Department, University of California, Santa Barbara, CA 93106, USA.,INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.,Materials Department, University of California, Santa Barbara, CA 93106, USA.,School of Engineering, University of Aberdeen, King's College, Aberdeen AB24 3UE, UK
| | - Kimberly L Foster
- Mechanical Engineering Department, University of California, Santa Barbara, CA 93106, USA.,School of Science and Engineering, Tulane University, New Orleans, LA 70118, USA
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Wang Y, Kang V, Arzt E, Federle W, Hensel R. Strong Wet and Dry Adhesion by Cupped Microstructures. ACS APPLIED MATERIALS & INTERFACES 2019; 11:26483-26490. [PMID: 31241296 PMCID: PMC6660100 DOI: 10.1021/acsami.9b07969] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 06/26/2019] [Indexed: 06/09/2023]
Abstract
Recent advances in bio-inspired microfibrillar adhesives have resulted in technologies that allow reliable attachment to a variety of surfaces. Because capillary and van der Waals forces are considerably weakened underwater, fibrillar adhesives are however far less effective in wet environments. Although various strategies have been proposed to achieve strong reversible underwater adhesion, strong adhesives that work both in air and underwater without additional surface treatments have yet to be developed. In this study, we report a novel design-cupped microstructures (CM)-that generates strong controllable adhesion in air and underwater. We measured the adhesive performance of cupped polyurethane microstructures with three different cup angles (15, 30, and 45°) and the same cup diameter of 100 μm in dry and wet conditions in comparison to standard mushroom-shaped microstructures (MSMs) of the same dimensions. In air, 15°CM performed comparably to the flat MSM of the same size with an adhesion strength (force per real contact area) of up to 1.3 MPa, but underwater, 15°CM achieved 20 times stronger adhesion than MSM (∼1 MPa versus ∼0.05 MPa). Furthermore, the cupped microstructures exhibit self-sealing properties, whereby stronger pulls lead to longer stable attachment and much higher adhesion through the formation of a better seal.
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Affiliation(s)
- Yue Wang
- INM − Leibniz Institute for New Materials, Campus D2 2, Saarbrücken 66123, Germany
| | - Victor Kang
- Department
of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Eduard Arzt
- INM − Leibniz Institute for New Materials, Campus D2 2, Saarbrücken 66123, Germany
- Department
of Materials Science and Engineering, Saarland
University, Campus D2
2, Saarbrücken 66123, Germany
| | - Walter Federle
- Department
of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - René Hensel
- INM − Leibniz Institute for New Materials, Campus D2 2, Saarbrücken 66123, Germany
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43
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Simaite A, Spenko M. Evaluation of silicone elastomers as structural materials for microstructured adhesives. BIOINSPIRATION & BIOMIMETICS 2019; 14:046005. [PMID: 31075783 DOI: 10.1088/1748-3190/ab20e6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Microstructured (sometimes referred to as gecko-like) adhesives have numerous advantages over flat films, especially for practical applications on non-ideal surfaces that may be uneven or contaminated with dust. However, due to interdependence among material surface and bulk properties, the best material to fabricate such adhesives is still unknown. In this work, we analyzed eleven commercially available silicone elastomers to evaluate their use as flat and microstructured adhesives to address multiple material related questions that may impact the choice of the 'best' material for microstructured dry adhesives. To illustrate the applicability of the measured properties to modeling microstructured surfaces, we use stalk-shaped microstructures, whose contact mechanics are well understood. We demonstrate that there is no correlation between the adhesion strength of flat and microstructured adhesives; while bulk dissipation is the most important factor influencing the adhesion strength of flat elastomers, after microstructurization, interface toughness becomes more important. Therefore, microstructured elastomers loaded with high surface energy additives may demonstrate higher adhesion than their flat counterparts. We also compare the adhesion of flat and microstructured silicone elastomers on rough substrates. In this case, we show that while flat elastomer adhesion decreases with increasing substrate roughness, microstructured silicone adhesion actually increases with increasing roughness up to 0.19 [Formula: see text]m. This is the first time an increase in adhesion strength on rough surfaces is reported for materials stiffer than 1.0 MPa.
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Affiliation(s)
- Aiva Simaite
- Illinois Institute of Technology, Mechanical, Materials and Aerospace Engineering, Chicago, IL 60616, United States of America
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44
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Alizadehyazdi V, Simaite A, Spenko M. Evaluation of Material Properties for Practical Microstructured Adhesives: Low Dust Adhesion and High Shear Strength. ACS APPLIED MATERIALS & INTERFACES 2019; 11:8654-8666. [PMID: 30715840 DOI: 10.1021/acsami.8b19895] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The development of microstructure (gecko-like) adhesives has focused almost solely on their adhesive strength. However, for practical applications, especially in real-world environments, the adhesive's long-term performance is arguably equally important. One impediment to long-term viability is the adhesive's susceptibility to contamination. It is a challenge to develop an adhesive that can both adhere to a substrate while not becoming contaminated with dust and debris. In response, this paper experimentally explores the effect of modulus of elasticity, work of separation, and work of adhesion (adhesion energy) on the shear stress and particle detachment capabilities of wedge-shaped, directional microstructured adhesives. Particle removal is evaluated using both noncontact cleaning methods (centripetal force and electrostatic particle repulsion) and a dry contact cleaning method (load-drag-unload test). Results show that for a material with a high work of separation, high elastic modulus, and low work of adhesion, it is possible to create a microstructured adhesive with both high shear stress strength and low adhesion to dust particles. Results also show that, for dry contact cleaning, shear stress recovery mostly stems from particle rolling and not particle sliding. Moreover, shear test results show that augmenting the microstructured adhesive with electrostatic adhesion can reduce the negative effects on adhesion of a high elastic modulus materials' conformability to a substrate by providing a preload to the microstructured elements. Last, this paper is the first to report on a electrostatic/gecko-like adhesive that uses its electrostatic elements for both adhesion and dust repulsion; they were reported separately before.
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Affiliation(s)
- Vahid Alizadehyazdi
- Mechanical, Materials, and Aerospace Engineering , Illinois Institute of Technology , Chicago , Illinois 60616 , United States
| | - Aiva Simaite
- Mechanical, Materials, and Aerospace Engineering , Illinois Institute of Technology , Chicago , Illinois 60616 , United States
| | - Matthew Spenko
- Mechanical, Materials, and Aerospace Engineering , Illinois Institute of Technology , Chicago , Illinois 60616 , United States
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45
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van Assenbergh P, Fokker M, Langowski J, van Esch J, Kamperman M, Dodou D. Pull-off and friction forces of micropatterned elastomers on soft substrates: the effects of pattern length scale and stiffness. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2019; 10:79-94. [PMID: 30680281 PMCID: PMC6334791 DOI: 10.3762/bjnano.10.8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 12/11/2018] [Indexed: 06/09/2023]
Abstract
The adhesiveness of biological micropatterned adhesives primarily relies on their geometry (e.g., feature size, architecture) and material properties (e.g., stiffness). Over the last few decades, researchers have been mimicking the geometry and material properties of biological micropatterned adhesives. The performance of these biomimetic micropatterned adhesives is usually tested on hard substrates. Much less is known about the effect of geometry, feature size, and material properties on the performance of micropatterned adhesives when the substrate is deformable. Here, micropatterned adhesives of two stiffness degrees (Young's moduli of 280 and 580 kPa) were fabricated from poly(dimethylsiloxane) (PDMS) and tested on soft poly(vinyl alcohol) (PVA) substrates of two stiffness degrees (12 and 18 kPa), and on hard glass substrates as a reference. An out-of-the-cleanroom colloidal lithographic approach was successfully expanded to fabricate adhesives with two geometries, namely dimples with and without a terminal layer. Dimples without a terminal layer were fabricated on two length scales, namely with sub-microscale and microscale dimple diameters. The cross section of samples with a terminal layer showed voids with a spherical shape, separated by hourglass-shaped walls. These voids penetrate the terminal layer, resulting in an array of holes at the surface. We found that on soft substrates, generally, the size of the dimples did not affect pull-off forces. The positive effects of sub-microscale features on pull-off and friction forces, such as defect control and crack trapping, as reported in the literature for hard substrates, seem to disappear on soft substrates. The dimple geometry with a terminal layer generated significantly higher pull-off forces compared to other geometries, presumably due to interlocking of the soft substrate into the holes of the terminal layer. Pull-off from soft substrates increased with the substrate stiffness for all tested geometries. Friction forces on soft substrates were the highest for microscale dimples without a terminal layer, likely due to interlocking of the soft substrate between the dimples.
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Affiliation(s)
- Peter van Assenbergh
- Biomechanical Engineering Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
| | - Marike Fokker
- Biomechanical Engineering Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
| | - Julian Langowski
- Experimental Zoology Group, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, The Netherlands
| | - Jan van Esch
- Chemical Engineering Department, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Marleen Kamperman
- Polymer Science, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Dimitra Dodou
- Biomechanical Engineering Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
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Yu D, Beckelmann D, Opsölder M, Schäfer B, Moh K, Hensel R, de Oliveira PW, Arzt E. Roll-to-Roll Manufacturing of Micropatterned Adhesives by Template Compression. MATERIALS 2018; 12:ma12010097. [PMID: 30597944 PMCID: PMC6337371 DOI: 10.3390/ma12010097] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 12/19/2018] [Accepted: 12/21/2018] [Indexed: 12/04/2022]
Abstract
For the next generation of handling systems, reversible adhesion enabled by micropatterned dry adhesives exhibits high potential. The versatility of polymeric micropatterns in handling objects made from various materials has been demonstrated by several groups. However, specimens reported in most studies have been restricted to the laboratory scale. Upscaling the size and quantity of micropatterned adhesives is the next step to enable successful technology transfer. Towards this aim, we introduce a continuous roll-to-roll replication process for fabrication of high-performance, mushroom-shaped micropatterned dry adhesives. The micropatterns were made from UV-curable polyurethane acrylates. To ensure the integrity of the complex structure during the fabrication process, flexible templates were used. The compression between the template and the wet prepolymer coating was investigated to optimize replication results without structural failures, and hence, to improve adhesion. As a result, we obtained micropatterned adhesive tapes, 10 cm in width and several meters in length, with adhesion strength about 250 kPa to glass, suitable for a wide range of applications.
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Affiliation(s)
- Dan Yu
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
| | - Dirk Beckelmann
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
| | - Michael Opsölder
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
| | - Bruno Schäfer
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
| | - Karsten Moh
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
| | - René Hensel
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
| | | | - Eduard Arzt
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
- Department of Materials Science and Engineering, Saarland University, 66123 Saarbrücken, Germany.
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47
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Velasco-Hogan A, Xu J, Meyers MA. Additive Manufacturing as a Method to Design and Optimize Bioinspired Structures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1800940. [PMID: 30133816 DOI: 10.1002/adma.201800940] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 05/11/2018] [Indexed: 06/08/2023]
Abstract
Additive manufacturing (AM) is a current technology undergoing rapid development that is utilized in a wide variety of applications. In the field of biological and bioinspired materials, additive manufacturing is being used to generate intricate prototypes to expand our understanding of the fundamental structure-property relationships that govern nature's spectacular mechanical performance. Herein, recent advances in the use of AM for improving the understanding of the structure-property relationship in biological materials and for the production of bioinspired materials are reviewed. There are four essential components to this work: a) extracting defining characteristics of biological designs, b) designing 3D-printed prototypes, c) performing mechanical testing on 3D-printed prototypes to understand fundamental mechanisms at hand, and d) optimizing design for tailorable performance. It is intended to highlight how the various types of additive manufacturing methods are utilized, to unravel novel discoveries in the field of biological materials. Since AM processing techniques have surpassed antiquated limitations, especially with respect to spatial scales, there has been a surge in their demand as an integral tool for research. In conclusion, current challenges and the technical perspective for further development of bioinspired materials using AM are discussed.
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Affiliation(s)
| | - Jun Xu
- Department of Automotive Engineering, School of Transportation Science and Engineering, Advanced Vehicle Research Center (AVRC), Beihang University, Beijing, 100191, China
| | - Marc A Meyers
- University of California, San Diego, La Jolla, CA, 92093, USA
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48
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Li M, Dai Q, Huang W, Wang X. Pillar versus dimple patterned surfaces for wettability and adhesion with varying scales. J R Soc Interface 2018; 15:rsif.2018.0681. [PMID: 30429264 DOI: 10.1098/rsif.2018.0681] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 10/17/2018] [Indexed: 11/12/2022] Open
Abstract
Inspired by biological topographical surfaces, micropatterned elastomeric surfaces with square pillars and dimples of different geometry scales were fabricated. Their wettability and adhesion properties with various liquids were systematically investigated and compared with flat surfaces. Interesting results were obtained in the case of silicone oil (the toe-pad-like wetting case) in that the scale-dependent wettability and adhesion performed inversely for pillars and dimples. Micropillars significantly enhanced the surface wettability with a geometry scale dependence, whereas the dimples suppressed the wettability independent of the geometry scale. The adhesion force of the micropillars increased with an increase of the geometry scale. However, in the case of the micro-dimples, the adhesion force obviously decreased with an increase of the geometry scale. This behaviour was attributed to the fact that pillars are 'open' to oil but dimples are 'close' to oil, presenting different orientations to the solid-liquid interface.
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Affiliation(s)
- Meng Li
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, People's Republic of, China
| | - Qingwen Dai
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, People's Republic of, China
| | - Wei Huang
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, People's Republic of, China
| | - Xiaolei Wang
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, People's Republic of, China
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49
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Qiao S, Wang L, Ha KH, Lu N. Suction effects of craters under water. SOFT MATTER 2018; 14:8509-8520. [PMID: 30349915 DOI: 10.1039/c8sm01601a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Octopus-inspired cratered surfaces have recently emerged as a new class of reusable physical adhesives. Preload-dependent adhesion and enhanced adhesion under water distinguish them from the well-studied gecko-inspired pillared surfaces. Despite growing experimental evidence, modeling frameworks and mechanistic understanding of cratered surfaces are still very limited. We recently developed a framework to evaluate suction forces produced by isolated craters in air. In this paper, we focus on underwater craters. The suction force-preload relation predicted by this framework has been validated by experiments carried out with an incompressible fluid under small and moderate preloads. Our model breaks down under a large preload due to multiple possible reasons including liquid vaporization. A direct comparison between liquid and air-filled craters has been carried out and the dependence on the depth of water has been revealed. We find that the suction forces generated by underwater craters scale with the specimen modulus but exhibit non-monotonic dependence on the aspect ratio of the craters.
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Affiliation(s)
- Shutao Qiao
- Center for Mechanics of Solids, Structures and Materials, Department of Aerospace Engineering and Engineering Mechanics, the University of Texas at Austin, 210 E. 24th St, Austin, TX 78712, USA.
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50
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Tunable Adhesion for Bio-Integrated Devices. MICROMACHINES 2018; 9:mi9100529. [PMID: 30424462 PMCID: PMC6215118 DOI: 10.3390/mi9100529] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 10/14/2018] [Accepted: 10/16/2018] [Indexed: 02/03/2023]
Abstract
With the rapid development of bio-integrated devices and tissue adhesives, tunable adhesion to soft biological tissues started gaining momentum. Strong adhesion is desirable when used to efficiently transfer vital signals or as wound dressing and tissue repair, whereas weak adhesion is needed for easy removal, and it is also the essential step for enabling repeatable use. Both the physical and chemical properties (e.g., moisture level, surface roughness, compliance, and surface chemistry) vary drastically from the skin to internal organ surfaces. Therefore, it is important to strategically design the adhesive for specific applications. Inspired largely by the remarkable adhesion properties found in several animal species, effective strategies such as structural design and novel material synthesis were explored to yield adhesives to match or even outperform their natural counterparts. In this mini-review, we provide a brief overview of the recent development of tunable adhesives, with a focus on their applications toward bio-integrated devices and tissue adhesives.
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