51
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Li Q, Popov VL. Adhesive contact of rough brushes. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2018; 9:2405-2412. [PMID: 30254835 PMCID: PMC6142746 DOI: 10.3762/bjnano.9.225] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 08/15/2018] [Indexed: 06/08/2023]
Abstract
The adhesive contact between a rough brush-like structure and an elastic half-space is numerically simulated using the fast Fourier transform (FFT)-based boundary element method and the mesh-dependent detachment criterion of Pohrt and Popov. The problem is of interest in light of the discussion of the role of contact splitting in the adhesion strength of gecko feet and structured biomimetic materials. For rigid brushes, the contact splitting does not enhance adhesion even if all pillars of the brush are positioned at the same height. Introducing statistical scatter of height leads to a further decrease of the maximum adhesive strength. At the same time, the pull-off force becomes dependent on the previously applied compression force and disappears completely at some critical roughness. For roughness with a subcritical value, the pressure dependence of the pull-off force qualitatively follows the known theory of Fuller and Tabor with moderate modification due to finite size effect of the brush.
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Affiliation(s)
- Qiang Li
- Berlin University of Technology, 10623 Berlin, Germany
| | - Valentin L Popov
- Berlin University of Technology, 10623 Berlin, Germany
- National Research Tomsk State University, 634050 Tomsk, Russia
- National Research Tomsk Polytechnic University, 634050 Tomsk, Russia
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52
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Kim JK, Varenberg M. Biomimetic wall-shaped adhesive microstructure for shear-induced attachment: the effects of pulling angle and preliminary displacement. J R Soc Interface 2018; 14:rsif.2017.0832. [PMID: 29237827 DOI: 10.1098/rsif.2017.0832] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 11/21/2017] [Indexed: 11/12/2022] Open
Abstract
To date, a handful of different gecko-like adhesives inspired by spatula-shaped attachment hairs have been suggested based on wedge and flap geometry of contact elements. However, while these surface designs have been shown to have directionality in adhesion, high friction, long lifetime and the ability to work in vacuum, an experimental verification of the very basic concept of the pulling angle effect has not yet been reported. To close this gap, here we use wall-shaped adhesive microstructures of three different flap heights to systematically study the effect of pulling angle on the normal and tangential components of the pull-off force tested at different preliminary tangential displacements. In accord with the prediction of the Kendall model for the normal component of peeling force, there is an optimal normal force that is required to detach the wall-shaped adhesive microstructure. The optimum is obtained at about half the distance needed to initiate sliding and at pulling angles that range within 60-90°, which suggests that the wall-shaped microstructure can tolerate relatively large inaccuracies in the loading direction. The increase of the attachment force with increasing flap height is found to correlate with the flap thickness, which decreased with increasing flap height.
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Affiliation(s)
- Jae-Kang Kim
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Michael Varenberg
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
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53
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Kizilkan E, Gorb SN. Bioinspired Further Enhanced Dry Adhesive by the Combined Effect of the Microstructure and Surface Free-Energy Increase. ACS APPLIED MATERIALS & INTERFACES 2018; 10:26752-26758. [PMID: 30010312 DOI: 10.1021/acsami.8b06686] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Silicone elastomers are known for having low surface free energies generally leading to poor adhesive performances. This surface characteristic can be enhanced by plasma treatments. The microstructured silicone elastomer surfaces can demonstrate superior adhesive performance that is more than 10 times higher in terms of pull-off forces, compared to their unstructured counterpart. Here, we have demonstrated that the combination of these two methods further enhances adhesive performance, especially when the surfaces are biomimetic micro/nanopatterned with, e.g., beetle-inspired mushroom-shaped adhesive microstructure (MSAMS). The plasma treatment time and pressure parameters were varied for the unstructured and MSAMS poly(vinylsiloxane) surfaces to find optimum parameters for maximum adhesion performance. Air plasma treatment induced average adhesive enhancement forces up to 30% on the unstructured surface, but the MSAMS surface demonstrated an enhancement of adhesive forces up to 91% higher than that of an untreated, microstructured control, despite the plasma-treated surface area of the structured surface being only 50% of that of the unstructured surface. High-speed video-recordings of individual microstructures in contact with a glass surface shows that the origin of the adhesion enhancement is due to the special detachment mechanism of individual microstructures that allows sustaining a wider contact area at detachment. We believe that this integration of the plasma treatment with MSAMS suggests a versatile way of functionalization that can further advance the adhesive ability of low-surface-energy polymer surfaces.
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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
| | - 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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54
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Rao P, Sun TL, Chen L, Takahashi R, Shinohara G, Guo H, King DR, Kurokawa T, Gong JP. Tough Hydrogels with Fast, Strong, and Reversible Underwater Adhesion Based on a Multiscale Design. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801884. [PMID: 29939425 DOI: 10.1002/adma.201801884] [Citation(s) in RCA: 151] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 04/30/2018] [Indexed: 06/08/2023]
Abstract
Hydrogels have promising applications in diverse areas, especially wet environments including tissue engineering, wound dressing, biomedical devices, and underwater soft robotics. Despite strong demands in such applications and great progress in irreversible bonding of robust hydrogels to diverse synthetic and biological surfaces, tough hydrogels with fast, strong, and reversible underwater adhesion are still not available. Herein, a strategy to develop hydrogels demonstrating such characteristics by combining macroscale surface engineering and nanoscale dynamic bonds is proposed. Based on this strategy, excellent underwater adhesion performance of tough hydrogels with dynamic ionic and hydrogen bonds, on diverse substrates, including hard glasses, soft hydrogels, and biological tissues is obtained. The proposed strategy can be generalized to develop other soft materials with underwater adhesion.
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Affiliation(s)
- Ping Rao
- Graduate School of Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Tao Lin Sun
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
- Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, 001-0021, Japan
- South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Liang Chen
- Graduate School of Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Riku Takahashi
- Graduate School of Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Gento Shinohara
- Department of Zoology, National Museum of Nature and Science, Tsukuba, 305-0005, Japan
| | - Hui Guo
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Daniel R King
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
- Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, 001-0021, Japan
| | - Takayuki Kurokawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
- Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, 001-0021, Japan
| | - Jian Ping Gong
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
- Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, 001-0021, Japan
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55
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Yang J, Włodarczyk-Biegun MK, Filippov A, Akerboom S, Dompé M, van Hees IA, Mocan M, Kamperman M. Functional Polymeric Materials Inspired by Geckos, Mussels, and Spider Silk. MACROMOL CHEM PHYS 2018. [DOI: 10.1002/macp.201800051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Juan Yang
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
| | | | - Alexei Filippov
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
| | - Sabine Akerboom
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
| | - Marco Dompé
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
| | - Ilse A. van Hees
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
| | - Merve Mocan
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
| | - Marleen Kamperman
- Physical Chemistry and Soft Matter; Wageningen University & Research; Stippeneng 4 6708 WE Wageningen The Netherlands
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56
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Brely L, Bosia F, Pugno NM. Emergence of the interplay between hierarchy and contact splitting in biological adhesion highlighted through a hierarchical shear lag model. SOFT MATTER 2018; 14:5509-5518. [PMID: 29923589 DOI: 10.1039/c8sm00507a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Contact unit size reduction is a widely studied mechanism as a means to improve adhesion in natural fibrillar systems, such as those observed in beetles or geckos. However, these animals also display complex structural features in the way the contact is subdivided in a hierarchical manner. Here, we study the influence of hierarchical fibrillar architectures on the load distribution over the contact elements of the adhesive system, and the corresponding delamination behaviour. We present an analytical model to derive the load distribution in a fibrillar system loaded in shear, including hierarchical splitting of contacts, i.e. a "hierarchical shear-lag" model that generalizes the well-known shear-lag model used in mechanics. The influence on the detachment process is investigated introducing a numerical procedure that allows the derivation of the maximum delamination force as a function of the considered geometry, including statistical variability of local adhesive energy. Our study suggests that contact splitting generates improved adhesion only in the ideal case of extremely compliant contacts. In real cases, to produce efficient adhesive performance, contact splitting needs to be coupled with hierarchical architectures to counterbalance high load concentrations resulting from contact unit size reduction, generating multiple delamination fronts and helping to avoid detrimental non-uniform load distributions. We show that these results can be summarized in a generalized adhesion scaling scheme for hierarchical structures, proving the beneficial effect of multiple hierarchical levels. The model can thus be used to predict the adhesive performance of hierarchical adhesive structures, as well as the mechanical behaviour of composite materials with hierarchical reinforcements.
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Affiliation(s)
- Lucas Brely
- Department of Physics and "Nanostructured Interfaces and Surfaces" Inter-Departmental Centre, Università di Torino, Via P. Giuria 1, 10125, Torino, Italy
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57
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Kizilkan E, Gorb SN. Combined Effect of the Microstructure and Underlying Surface Curvature on the Performance of Biomimetic Adhesives. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1704696. [PMID: 29280284 DOI: 10.1002/adma.201704696] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 11/13/2017] [Indexed: 06/07/2023]
Abstract
The importance of the geometry of the micro-/nanosized attachment elements for adhesive characteristics of gecko-inspired microstructured surfaces has been comprehensively discussed in recent years. Due to the complex hierarchical structure of these systems, they possess a broad range of adhesion control capabilities by either passive or active adaptability of their underlying structures to the specific substrate and/or behavioral situation. Here, the influence of macroscopic geometry of backing layers hosting biomimetic microstructured surfaces is examined. The flat, convex, and concave macroscopic configurations of the bioinspired microstructured adhesive surfaces are examined on their adhesive performance under varying degrees of curvature and preloads. Microstructured surfaces demonstrated an adhesion range differing by up to a factor of 2 alone through varying backing layer configuration. The results can aid in understanding the influence of curvature geometry on hierarchically structured adhesive systems and the implementation of biomimetic structured surfaces in applications such as robots and grippers optimized for different sized objects.
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Affiliation(s)
- Emre Kizilkan
- Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, 24118, Kiel, Germany
| | - Stanislav N Gorb
- Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, 24118, Kiel, Germany
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58
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van Assenbergh P, Meinders E, Geraedts J, Dodou D. Nanostructure and Microstructure Fabrication: From Desired Properties to Suitable Processes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1703401. [PMID: 29573546 DOI: 10.1002/smll.201703401] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 11/30/2017] [Indexed: 05/25/2023]
Abstract
When designing a new nanostructure or microstructure, one can follow a processing-based manufacturing pathway, in which the structure properties are defined based on the processing capabilities of the fabrication method at hand. Alternatively, a performance-based pathway can be followed, where the envisioned performance is first defined, and then suitable fabrication methods are sought. To support the latter pathway, fabrication methods are here reviewed based on the geometric and material complexity, resolution, total size, geometric and material diversity, and throughput they can achieve, independently from processing capabilities. Ten groups of fabrication methods are identified and compared in terms of these seven moderators. The highest resolution is obtained with electron beam lithography, with feature sizes below 5 nm. The highest geometric complexity is attained with vat photopolymerization. For high throughput, parallel methods, such as photolithography (≈101 m2 h-1 ), are needed. This review offers a decision-making tool for identifying which method to use for fabricating a structure with predefined properties.
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Affiliation(s)
- Peter van Assenbergh
- Department of BioMechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Mekelweg 2, 2628, CD, Delft, The Netherlands
| | - Erwin Meinders
- AMSYSTEMS Center, De Lismortel 31, 5612, AR, Eindhoven, The Netherlands
| | - Jo Geraedts
- Faculty of Industrial Design Engineering, Delft University of Technology, Landbergstraat 15, 2628, CE, Delft, The Netherlands
| | - Dimitra Dodou
- Department of BioMechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Mekelweg 2, 2628, CD, Delft, The Netherlands
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59
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Cho Y, Minsky HK, Jiang Y, Yin K, Turner KT, Yang S. Shear Adhesion of Tapered Nanopillar Arrays. ACS APPLIED MATERIALS & INTERFACES 2018; 10:11391-11397. [PMID: 29570269 DOI: 10.1021/acsami.8b02303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Tapered nanopillars with various cross sections, including cone-shaped, stepwise, and pencil-like structures (300 nm in diameter at the base of the pillars and 1.1 μm in height), are prepared from epoxy resin templated by nanoporous anodic aluminum oxide (AAO) membranes. The effect of pillar geometry on the shear adhesion behavior of these nanopillar arrays is investigated via sliding experiments in a nanoindentation system. In a previous study of arrays with the same geometry, it was shown that cone-shaped nanopillars exhibit the highest adhesion under normal loading while stepwise and pencil-like nanopillars exhibit lower normal adhesion strength due to significant deformation of the pillars that occurs with increasing indentation depth. Contrary to the previous studies, here, we show that pencil-like nanopillars exhibit the highest shear adhesion strength at all indentation depths among three types of nanopillar arrays and that the shear adhesion increases with greater indentation depth due to the higher bending stiffness and closer packing of the pencil-like nanopillar array. Finite element simulations are used to elucidate the deformation of the pillars during the sliding experiments and agree with the nanoindentation-based sliding measurements. The experiments and finite element simulations together demonstrate that the shape of the nanopillars plays a key role in shear adhesion and that the mechanism is quite different from that of adhesion under normal loading.
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Affiliation(s)
- Younghyun Cho
- Department of Materials Science and Engineering , University of Pennsylvania , 3231 Walnut Street , Philadelphia , Pennsylvania 19104 , United States
- Energy Efficiency and Materials Research Division , Korea Institute of Energy Research , 152 Gajeong-ro, Yuseong-gu , Daejeon 305-343 , Republic of Korea
| | - Helen K Minsky
- Department of Mechanical Engineering and Applied Mechanics , University of Pennsylvania , 220 South 33rd Street , Philadelphia , Pennsylvania 19104 , United States
| | - Yijie Jiang
- Department of Mechanical Engineering and Applied Mechanics , University of Pennsylvania , 220 South 33rd Street , Philadelphia , Pennsylvania 19104 , United States
| | - Kaiyang Yin
- Department of Materials Science and Engineering , University of Pennsylvania , 3231 Walnut Street , Philadelphia , Pennsylvania 19104 , United States
| | - Kevin T Turner
- Department of Mechanical Engineering and Applied Mechanics , University of Pennsylvania , 220 South 33rd Street , Philadelphia , Pennsylvania 19104 , United States
| | - Shu Yang
- Department of Materials Science and Engineering , University of Pennsylvania , 3231 Walnut Street , Philadelphia , Pennsylvania 19104 , United States
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60
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Alizadehyazdi V, Modabberifar M, Mahmoudzadeh Akherat SMJ, Spenko M. Electrostatic self-cleaning gecko-like adhesives. J R Soc Interface 2018; 15:20170714. [PMID: 29695604 PMCID: PMC5938576 DOI: 10.1098/rsif.2017.0714] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 03/29/2018] [Indexed: 11/12/2022] Open
Abstract
This paper describes the use of the electrostatic element of an electrostatic/gecko-like adhesive to repel dust particles, which have been shown to significantly affect adhesion and reliability. The result is a non-destructive, non-contact cleaning method that can be used in conjunction with other cleaning techniques, many of which rely on physical contact between the fibrillar adhesive and substrate. The paper focuses on experimental evaluation of the repulsion of 100 μm glass beads as a function of wave shape, frequency, phase number and electrode direction in relation to the gecko-like features. Results show that a two-phase square wave with the lowest practically feasible frequency can remove 100 μm glass beads from a directional gecko-like adhesive with up to 70% efficiency. Finally, using the optimized electrostatic cleaning properties, results show an approximately 25% recovery in shear stress on a rough glass for three contaminated directional gecko-like adhesives after contact with a dusty table.
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Affiliation(s)
- Vahid Alizadehyazdi
- Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Mehdi Modabberifar
- Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak 38156-88849, Iran
| | | | - Matthew Spenko
- Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA
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61
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Patil S, Deshpande T, Chaudhari N, Singh YRG, Raut J, Joshi YM, Sharma A. Making Nonsticky Surfaces of Sticky Materials: Self-Organized Microtexturing of Viscoelastic Elastomeric Layers by Tearing. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:3767-3774. [PMID: 29505263 DOI: 10.1021/acs.langmuir.7b04389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fabrication of large area, multiscale microtextured surfaces engineered for antiadhesion properties remains a challenge. Compared to an elastic surface, viscoelastic solids show much higher surface stickiness, tack, and adhesion owing to the increased contact area and energy dissipation. Here, we show a simple, low cost, large-area and high throughput method with roll-to-roll compatibility to fabricate multiscale, rough microstructures resistant to adhesion in a viscoelastic layer by controlled tearing of viscous film. Even a high adhesive strength viscoelastic solid layer, such as partially cured PDMS, is made nonsticky simply by its controlled tearing. The torn surface shows a fracture induced, self-organized leaflike micropattern resistant to sticking. The topography and adhesion strength of these structures are readily tuned by changing the tearing speed and the film thickness. The microtexture displays a springlike recovery, low adhesive strength, and easy release properties even under the high applied loads.
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Affiliation(s)
- Sandip Patil
- Department of Chemical Engineering , Indian Institute of Technology , Kanpur - 208016 , U.P. , India
| | - Tushar Deshpande
- Department of Chemical Engineering , Indian Institute of Technology , Kanpur - 208016 , U.P. , India
| | - Nayantika Chaudhari
- Department of Chemical Engineering , Indian Institute of Technology , Kanpur - 208016 , U.P. , India
| | - Yogesh R G Singh
- Department of Chemical Engineering , Indian Institute of Technology , Kanpur - 208016 , U.P. , India
| | - Janhavi Raut
- Unilever R&D , 64 Main Road, Whitefield , Bangalore 560066 , India
| | - Yogesh M Joshi
- Department of Chemical Engineering , Indian Institute of Technology , Kanpur - 208016 , U.P. , India
| | - Ashutosh Sharma
- Department of Chemical Engineering , Indian Institute of Technology , Kanpur - 208016 , U.P. , India
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62
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Amador GJ, Endlein T, Sitti M. Soiled adhesive pads shear clean by slipping: a robust self-cleaning mechanism in climbing beetles. J R Soc Interface 2018. [PMID: 28637914 DOI: 10.1098/rsif.2017.0134] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Animals using adhesive pads to climb smooth surfaces face the problem of keeping their pads clean and functional. Here, a self-cleaning mechanism is proposed whereby soiled feet would slip on the surface due to a lack of adhesion but shed particles in return. Our study offers an in situ quantification of self-cleaning performance in fibrillar adhesives, using the dock beetle as a model organism. After beetles soiled their pads by stepping into patches of spherical beads, we found that their gait was significantly affected. Specifically, soiled pads slipped 10 times further than clean pads, with more particles deposited for longer slips. Like previous studies, we found that particle size affected cleaning performance. Large (45 μm) beads were removed most effectively, followed by medium (10 μm) and small (1 μm). Consistent with our results from climbing beetles, force measurements on freshly severed legs revealed larger detachment forces of medium particles from adhesive pads compared to a flat surface, possibly due to interlocking between fibres. By contrast, dock leaves showed an overall larger affinity to the beads and thus reduced the need for cleaning. Self-cleaning through slippage provides a mechanism robust to particle size and may inspire solutions for artificial adhesives.
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Affiliation(s)
- Guillermo J Amador
- Department of Physical Intelligence, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Thomas Endlein
- Department of Physical Intelligence, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Metin Sitti
- Department of Physical Intelligence, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
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63
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Wang Z. Slanted Functional Gradient Micropillars for Optimal Bioinspired Dry Adhesion. ACS NANO 2018; 12:1273-1284. [PMID: 29357229 DOI: 10.1021/acsnano.7b07493] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
For biologically inspired dry adhesives, the fibrillar structure of the surface requires sufficient flexibility to form contacts and meanwhile high rigidity to maintain stability. This fundamental conflict has greatly hindered the advance of synthetic adhesives toward mass-scale and practical applications, where adhesion is desired to be simultaneously strong, durable, directional, and roughness-adaptive. In this work, we overcome such a long-term challenge by developing fibrillar structures that combine both slanted geometry and gradient material of micropillars. The termed slanted functional gradient pillars (s-FGPs), fabricated by a magnetically assisted mold replication technique, exhibit flexible tips for contacts, gradually stiffened stalks for reinforcement, slanted structure to give rise to anisotropy, and high aspect ratio (AR) to facilitate surface adaptation. We demonstrate that the material and structure of the s-FGPs complement each other, synergetic effects of which result in a multifunctional combination of adhesion properties including high strength (∼9 N/cm2 in shear), ultradurability (over 200 cycles of attachment/detachment without adhesion degradation), super anisotropy (anisotropic ratio of ∼7), and good adaptability to rough surfaces. The s-FGPs not only step forward the bioinspired adhesion toward optimized designs and performances for practical applications but may also open up other concepts for various high-AR and structurally stable fibrillar surfaces with emerging functionalities and applications in the fields of self-cleaning, superhydrophobicity, biosensors, energy harvesting, etc.
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Affiliation(s)
- Zhengzhi Wang
- Department of Engineering Mechanics, School of Civil Engineering, Wuhan University , Wuhan, Hubei 430072, China
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64
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Kundan KK, Ghatak A. The effect of shape on the fracture of a soft elastic gel subjected to shear load. SOFT MATTER 2018; 14:1365-1374. [PMID: 29383364 DOI: 10.1039/c7sm02392h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
For brittle solids, the fracture energy is the energy required to create a unit area of new surface through the process of division. For crosslinked materials, it is a function of the intrinsic properties like crosslinking density and bond strength of the crosslinks. Here we show that the energy released due to fracture can depend also on the shape of a joint made of this material. Our experiment involves two gel blocks connected via a thin gel disk. The disk is formed into different regular and exotic shapes, but with identical areas of cross-section. When one of the blocks is sheared with respect to the other, the shear load increases with vertical displacement, eventually causing a fracture at a threshold load. The maximum fracture load is different for different disks and among different regularly shaped disks, it is at a maximum for pentagon and hexagon shapes. The fracture energy release rate of the joint depends also on the aspect ratio (height/width) of the shapes. Our experiments also throw light on possible reasons for such a dependence on the shape of the joints.
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Affiliation(s)
- Krishna Kant Kundan
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, UP 208016, India.
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65
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Gecko Adhesion. Biomimetics (Basel) 2018. [DOI: 10.1007/978-3-319-71676-3_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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66
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Barreau V, Yu D, Hensel R, Arzt E. Elevated temperature adhesion of bioinspired polymeric micropatterns to glass. J Mech Behav Biomed Mater 2017; 76:110-118. [DOI: 10.1016/j.jmbbm.2017.04.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 04/04/2017] [Accepted: 04/05/2017] [Indexed: 11/16/2022]
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67
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Abdel-Aal HA. Surface structure and tribology of legless squamate reptiles. J Mech Behav Biomed Mater 2017; 79:354-398. [PMID: 29352677 DOI: 10.1016/j.jmbbm.2017.11.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 10/26/2017] [Accepted: 11/03/2017] [Indexed: 10/18/2022]
Abstract
Squamate reptiles (around 10,000 species of snakes and lizards) comprise a myriad of distinct terrestrial vertebrates. The diversity within this biological group offers a great opportunity for customized bio-inspired solutions that address a variety of current technological problems especially within the realm of surface engineering and tribology. One subgroup within squamata is of interest in that context, namely the legless reptiles (mainly snakes and few lizards). The promise of that group lies within their functional adaptation as manifested in optimized surface designs and locomotion that is distinguished by economy of effort even when functioning within hostile tribological environments. Legless reptiles are spread over a wide range in the planet, this geographical diversity demands customized response to local habitats. Customization, in turn, is facilitated through specialized surface design features. In legless reptiles, micro elements of texture, their geometry and topological layout advance mitigation of frictional effects both in locomotion and in general function. Lately, the synergy between functional traits and intrinsic surface features has emerged as focus of research across disciplines. Many investigations have sought to characterize the structural as well as the tribological response of legless species from an engineering point of view. Despite the sizable amount of data that have accumulated in the literature over the past two decades or so, no effort to review the available information, whence this review. This manuscript, therefore, endeavors to assess available data on surface metrology and tribological behavior of legless reptiles and to define aspects of that performance necessary to formulate an advanced paradigm for bio-inspired surface engineering.
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68
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Wolff JO, Wells D, Reid CR, Blamires SJ. Clarity of objectives and working principles enhances the success of biomimetic programs. BIOINSPIRATION & BIOMIMETICS 2017; 12:051001. [PMID: 28820140 DOI: 10.1088/1748-3190/aa86ff] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Biomimetics, the transfer of functional principles from living systems into product designs, is increasingly being utilized by engineers. Nevertheless, recurring problems must be overcome if it is to avoid becoming a short-lived fad. Here we assess the efficiency and suitability of methods typically employed by examining three flagship examples of biomimetic design approaches from different disciplines: (1) the creation of gecko-inspired adhesives; (2) the synthesis of spider silk, and (3) the derivation of computer algorithms from natural self-organizing systems. We find that identification of the elemental working principles is the most crucial step in the biomimetic design process. It bears the highest risk of failure (e.g. losing the target function) due to false assumptions about the working principle. Common problems that hamper successful implementation are: (i) a discrepancy between biological functions and the desired properties of the product, (ii) uncertainty about objectives and applications, (iii) inherent limits in methodologies, and (iv) false assumptions about the biology of the models. Projects that aim for multi-functional products are particularly challenging to accomplish. We suggest a simplification, modularisation and specification of objectives, and a critical assessment of the suitability of the model. Comparative analyses, experimental manipulation, and numerical simulations followed by tests of artificial models have led to the successful extraction of working principles. A searchable database of biological systems would optimize the choice of a model system in top-down approaches that start at an engineering problem. Only when biomimetic projects become more predictable will there be wider acceptance of biomimetics as an innovative problem-solving tool among engineers and industry.
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Affiliation(s)
- Jonas O Wolff
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia
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Drotlef DM, Amjadi M, Yunusa M, Sitti M. Bioinspired Composite Microfibers for Skin Adhesion and Signal Amplification of Wearable Sensors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1701353. [PMID: 28523760 DOI: 10.1002/adma.201701353] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 03/31/2017] [Indexed: 05/26/2023]
Abstract
A facile approach is proposed for superior conformation and adhesion of wearable sensors to dry and wet skin. Bioinspired skin-adhesive films are composed of elastomeric microfibers decorated with conformal and mushroom-shaped vinylsiloxane tips. Strong skin adhesion is achieved by crosslinking the viscous vinylsiloxane tips directly on the skin surface. Furthermore, composite microfibrillar adhesive films possess a high adhesion strength of 18 kPa due to the excellent shape adaptation of the vinylsiloxane tips to the multiscale roughness of the skin. As a utility of the skin-adhesive films in wearable-device applications, they are integrated with wearable strain sensors for respiratory and heart-rate monitoring. The signal-to-noise ratio of the strain sensor is significantly improved to 59.7 because of the considerable signal amplification of microfibrillar skin-adhesive films.
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Affiliation(s)
- Dirk-M Drotlef
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
| | - Morteza Amjadi
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
- Max Planck-ETH Center for Learning Systems, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
| | - Muhammad Yunusa
- 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
- Max Planck-ETH Center for Learning Systems, Max Planck Institute for Intelligent Systems, Stuttgart, 70569, Germany
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70
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Wang X, Tan D, Zhang X, Lei Y, Xue L. Effective Elastic Modulus of Structured Adhesives: From Biology to Biomimetics. Biomimetics (Basel) 2017; 2:E10. [PMID: 31105173 PMCID: PMC6352679 DOI: 10.3390/biomimetics2030010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/24/2017] [Accepted: 06/24/2017] [Indexed: 11/16/2022] Open
Abstract
Micro- and nano-hierarchical structures (lamellae, setae, branches, and spatulae) on the toe pads of many animals play key roles for generating strong but reversible adhesion for locomotion. The hierarchical structure possesses significantly reduced, effective elastic modulus (Eeff), as compared to the inherent elastic modulus (Einh) of the corresponding biological material (and therefore contributes to a better compliance with the counterpart surface). Learning from nature, three types of hierarchical structures (namely self-similar pillar structure, lamella⁻pillar hybrid structure, and porous structure) have been developed and investigated.
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Affiliation(s)
- Xin Wang
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan 430072, China.
| | - Di Tan
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan 430072, China.
| | - Xinyu Zhang
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan 430072, China.
| | - Yifeng Lei
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan 430072, China.
| | - Longjian Xue
- School of Power and Mechanical Engineering, Wuhan University, South Donghu Road 8, Wuhan 430072, China.
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71
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Gorumlu S, Aksak B. Sticking to rough surfaces using functionally graded bio-inspired microfibres. ROYAL SOCIETY OPEN SCIENCE 2017; 4:161105. [PMID: 28680663 PMCID: PMC5493905 DOI: 10.1098/rsos.161105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 05/09/2017] [Indexed: 06/07/2023]
Abstract
Synthetic fibrillar adhesives inspired by nature, most commonly by the gecko lizard, have been shown to strongly and repeatedly attach to smooth surfaces. These adhesives, mostly of monolithic construction, perform on par with their natural analogues on smooth surfaces but exhibit far inferior adhesive performance on rough surfaces. In this paper, we report on the adhesive performance of functionally graded microfibrillar adhesives based on a microfibre with a divergent end and a thin soft distal layer on rough surfaces. Monolithic and functionally graded fibre arrays were fabricated from polyurethanes and their adhesive performance on surfaces of varying roughness were quantified from force-distance data obtained using a custom adhesion measurement system. Average pull-off stress declined significantly with increasing roughness for the monolithic fibre array, dropping from 77 kPa on the smoothest (54 nm RMS roughness) to 19 kPa on the roughest (408 nm RMS roughness) testing surface. In comparison, pull-off stresses of 81 kPa and 63 kPa were obtained on the same respective smooth and rough surfaces with a functionally graded fibre array, which represents a more than threefold increase in adhesion to the roughest adhering surface. These results show that functionally graded fibrillar adhesives perform similar on all the testing surfaces unlike monolithic arrays and show potential as repeatable and reusable rough surface adhesives.
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Affiliation(s)
| | - Burak Aksak
- Author for correspondence: Burak Aksak e-mail:
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72
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Minsky HK, Turner KT. Composite Microposts with High Dry Adhesion Strength. ACS APPLIED MATERIALS & INTERFACES 2017; 9:18322-18327. [PMID: 28440627 DOI: 10.1021/acsami.7b01491] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Interfaces with enhanced and tunable adhesion have applications in a broad range of fields, including microtransfer printing of semiconductors, grippers on robots, and component handling in manufacturing. Here, a composite post structure with a stiff core and a compliant shell is used to achieve an enhanced adhesion under normal loading. Loading the composite structure in shear significantly reduces the effective adhesion strength, thus providing tunability. The composite posts can be used as stamps in microtransfer printing processes or as building blocks of large-area tunable surfaces composed of arrays of posts. Experimental measurements on composite posts with diameters of 200 μm show a peak adhesion strength of 1.5 MPa, a 9 times enhancement in adhesion relative to a homogeneous post under normal loading, and also that the adhesion can be reduced by nearly a factor of 7 through the application of shear. The adhesion behavior of these composite structures was also examined using finite element analysis, which provides an understanding of the mechanics of detachment. Finally, the composite adhesive posts were used as stamps in a microtransfer printing process in which 5 μm thick silicon membranes were retrieved and subsequently printed.
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Affiliation(s)
- H K Minsky
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania , Philadelphia 19104, United States
| | - Kevin T Turner
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania , Philadelphia 19104, United States
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73
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Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces. Proc Natl Acad Sci U S A 2017; 114:E4344-E4353. [PMID: 28507143 DOI: 10.1073/pnas.1620344114] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.
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74
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A Review of the State of Dry Adhesives: Biomimetic Structures and the Alternative Designs They Inspire. MICROMACHINES 2017. [PMCID: PMC6189926 DOI: 10.3390/mi8040125] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Robust and inexpensive dry adhesives would have a multitude of potential applications, but replicating the impressive adhesive organs of many small animals has proved challenging. A substantial body of work has been produced in recent years which has illuminated the many mechanical processes influencing a dry adhesive interface. The especially potent footpads of the tokay gecko have inspired researchers to develop and examine an impressive and diverse collection of artificial fibrillar dry adhesives, though study of tree frogs and insects demonstrate that successful adhesive designs come in many forms. This review discusses the current theoretical understanding of dry adhesive mechanics, including the observations from biological systems and the lessons learned by recent attempts to mimic them. Attention is drawn in particular to the growing contingent of work exploring ideas which are complimentary to or an alternative for fibrillar designs. The fundamentals of compliance control form a basis for dry adhesives made of composite and “smart,” stimuli-responsive materials including shape memory polymers. An overview of fabrication and test techniques, with a sampling of performance results, is provided.
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75
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Hu H, Tian H, Shao J, Li X, Wang Y, Wang Y, Tian Y, Lu B. Discretely Supported Dry Adhesive Film Inspired by Biological Bending Behavior for Enhanced Performance on a Rough Surface. ACS APPLIED MATERIALS & INTERFACES 2017; 9:7752-7760. [PMID: 28186403 DOI: 10.1021/acsami.6b14951] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Biologically inspired dry adhesion has recently become a research hot topic because of its practical significance in scientific research and instrumental technology. Yet, most of the current studies merely focus on borrowing the concept from some finer biological contact elements but lose sight of the foundation ones that play an equally important role in the adhesion functionality. Inspired by the bending behavior of the flexible foundation element of a gecko (lamellar skin) in attachment motion, in this study, a new type of dry adhesive structure was proposed, wherein a mushroom-shaped micropillar array behaving as a strongly adhesive layer was engineered on a discretely supported thin film. We experimentally observed and analytically modeled the structural deformation and found that the energy penalty could be largely reduced because of the partial shift from pillar bending to film bending. Such behavior is very analogous in functionality to the lamellar skin in a gecko's pads and is helpful in effectively limiting the damage of the contact interface, thus generating enhanced adhesion even on a rough surface.
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Affiliation(s)
- Hong Hu
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Hongmiao Tian
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Jinyou Shao
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Xiangming Li
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Yue Wang
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Yan Wang
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Yu Tian
- State Key Laboratory of Tribology, Tsinghua University , Beijing 10084, China
| | - Bingheng Lu
- Micro/Nanotechnology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
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76
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Suzuki H, Mitsuno K, Shiroguchi K, Tsugane M, Okano T, Dohi T, Tsuji T. One-step micromolding of complex 3D microchambers for single-cell analysis. LAB ON A CHIP 2017; 17:647-652. [PMID: 28150829 DOI: 10.1039/c6lc01313a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Herein we examined the extent of replicability of the PDMS microchamber device transferred from the master mold with complex 3D structures fabricated via micro stereolithography. Due to the elastomeric properties of PDMS, the reversely tapered micromold, with the diameter ratio of ∼5 from the largest to the narrowest part, was precisely transferred without breaking. We obtained the mathematical model to estimate the stress exerted on the mold during the demolding process. Finally, we tested the applicability of this unusual microchamber for single-cell trapping and an enzyme assay.
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Affiliation(s)
- Hiroaki Suzuki
- Department of Precision Mechanics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan.
| | - Kenta Mitsuno
- Department of Precision Mechanics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan.
| | - Katsuyuki Shiroguchi
- Laboratory for Integrative Omics, RIKEN Quantitative Biology Center (QBiC), 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan and Laboratory for Immunogenetics, RIKEN Center for Integrative Medical Sciences (IMS), 1-7-22, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan and JST PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Mamiko Tsugane
- Department of Precision Mechanics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan. and JSPS, 5-3-1, Kojimachi, Chiyoda-ku, Tokyo, 102-0083, Japan
| | - Taiji Okano
- Department of Precision Mechanics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan.
| | - Tetsuji Dohi
- Department of Precision Mechanics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan.
| | - Tomoaki Tsuji
- Department of Precision Mechanics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan.
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77
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Wang Y, Lehmann S, Shao J, Sameoto D. Adhesion Circle: A New Approach To Better Characterize Directional Gecko-Inspired Dry Adhesives. ACS APPLIED MATERIALS & INTERFACES 2017; 9:3060-3067. [PMID: 28038311 DOI: 10.1021/acsami.6b11708] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The number of different designs of directional gecko-inspired adhesives has proliferated over the past 15 years, but some basic characterization tools are still nonstandardized, which can make direct comparisons of different adhesives in the literature difficult. By far the most common type of test for directional adhesives, the load-drag-pull (LDP) test is useful but can miss substantial information on the exact behavior of gecko-inspired adhesives in a variety of loading conditions. Other test techniques, including angled approaches and pull-offs, have been employed by a few groups but they are not as widely adopted; peel tests can be employed but require a larger amount of adhesive material to use in the test, which is not always practical given some current manufacturing constraints. Very few tests have looked at the effect of off-main axis loads on the performance of directional adhesives, however, and this quality of performance may be very important in applications where direct control over displacements or angle of pull-off in pitch and yaw of the peeling interface may not be practical or possible. To address this overlooked area of characterization, we introduce a new test concept for anisotropic adhesives, the adhesion circle, and also compare how the radial normal adhesion performance is altered depending on whether the pull-off comes after a displacement drag or when pulled at a constant angle from vertical after a preload. Testing directional adhesive designs made with different geometries shows that unexpected behaviors at pull-off angles not in the direction of the strong-weak axis can sometimes be seen. The complete adhesion circle tests should help better design directional adhesives for scaled up performance, and can be completed with relatively simple hardware that is typically used in most current directional adhesive tests.
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Affiliation(s)
- Yue Wang
- Department of Mechanical Engineering, University of Alberta 10-203 Donadeo Innovation Centre for Engineering , 9211 116 St. NW, Edmonton, AB Canada , T6G 1H9
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Samuel Lehmann
- Department of Mechanical Engineering, University of Alberta 10-203 Donadeo Innovation Centre for Engineering , 9211 116 St. NW, Edmonton, AB Canada , T6G 1H9
| | - Jinyou Shao
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China
| | - Dan Sameoto
- Department of Mechanical Engineering, University of Alberta 10-203 Donadeo Innovation Centre for Engineering , 9211 116 St. NW, Edmonton, AB Canada , T6G 1H9
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78
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Shahsavan H, Salili SM, Jákli A, Zhao B. Thermally Active Liquid Crystal Network Gripper Mimicking the Self-Peeling of Gecko Toe Pads. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 27859776 DOI: 10.1002/adma.201604021] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 09/25/2016] [Indexed: 05/12/2023]
Abstract
Self-peeling of gecko toes is mimicked by integration of film-terminated fibrillar adhesives to hybrid nematic liquid crystal network (LCN) cantilevers. A soft gripper is developed based on the gecko-inspired attachment/detachment mechanism. Performance of the fabricated gripper for transportation of thin delicate objects is evaluated by the optimum mechanical strength of the LCN and the maximum size of the adhesive patch.
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Affiliation(s)
- Hamed Shahsavan
- Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Institute for Polymer Research, and Centre for Bioengineering and Biotechnology, 200 University Avenue W, Waterloo, ON, N2L 3G1, Canada
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH, 44242, USA
| | - Seyyed Muhammad Salili
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH, 44242, USA
| | - Antal Jákli
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH, 44242, USA
- Complex Fluids Group, Wigner Research Centre, H-1121, Budapest, Hungary
| | - Boxin Zhao
- Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Institute for Polymer Research, and Centre for Bioengineering and Biotechnology, 200 University Avenue W, Waterloo, ON, N2L 3G1, Canada
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79
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Pendyala P, Grewal HS, Kim HN, Cho IJ, Yoon ES. Individual Role of the Physicochemical Characteristics of Nanopatterns on Tribological Surfaces. ACS APPLIED MATERIALS & INTERFACES 2016; 8:30590-30600. [PMID: 27739687 DOI: 10.1021/acsami.6b10123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Nanoscale patterns have dimensions that are comparable to the length scales affected by intermolecular and surface forces. In this study, we systematically investigated the individual roles of curvature, surface energy, lateral stiffness, material, and pattern density in the adhesion and friction of nanopatterns. We fabricated cylindrical and mushroom-shaped polymer pattern geometries containing flat- and round-topped morphologies using capillary force lithography and nanodrawing techniques. We showed that the curvature, surface energy, and density of the patterns predominantly influenced the adhesive interactions, whereas lateral stiffness dominated friction by controlling the geometrical interaction between the indenter and pillar during sliding. Interestingly, in contrast to previous studies, cylindrical and mushroom-shaped pillars showed similar adhesion characteristics but very different frictional properties. Using fracture mechanics analysis, we showed that this phenomenon is due to a larger ratio of the mushroom flange thickness (t) to the radius of the pillar stem (ρ), and we proposed a design criterion for mushroom patterns to exhibit a geckolike effect. The most important result of our work is the discovery of a linear master curve in the graph of adhesion versus friction for pillars with similar lateral stiffness values that is independent of curvature, material, surface energy, and pattern density. These results will aid in the identification of simple pattern parameters that can be scaled to tune adhesion and friction and will help broaden the understanding of nanoscale topographical interactions.
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Affiliation(s)
- Prashant Pendyala
- Center for BioMicrosystems, Korea Institute of Science and Technology (KIST) , Seoul 02792, Republic of Korea
| | - Harpreet S Grewal
- Department of Mechanical Engineering, School of Engineering, Shiv Nadar University , Uttar Pradesh 201314, India
| | - Hong Nam Kim
- Center for BioMicrosystems, Korea Institute of Science and Technology (KIST) , Seoul 02792, Republic of Korea
| | - Il-Joo Cho
- Center for BioMicrosystems, Korea Institute of Science and Technology (KIST) , Seoul 02792, Republic of Korea
| | - Eui-Sung Yoon
- Center for BioMicrosystems, Korea Institute of Science and Technology (KIST) , Seoul 02792, Republic of Korea
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80
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Chaudhary OJ, Calius EP, Kennedy JV, Dickinson M, Loho T, Travas-Sejdic J. Poly(dimethylsiloxane) grafted with adhesive polymeric chains provide a route towards cost effective dry adhesives. Eur Polym J 2016. [DOI: 10.1016/j.eurpolymj.2016.08.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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81
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Im HS, Kim JU, Han S, Kim TI. Process, Design and Materials for Unidirectionally Tilted Polymeric Micro/Nanohairs and Their Adhesion Characteristics. Polymers (Basel) 2016; 8:polym8090326. [PMID: 30974600 PMCID: PMC6431841 DOI: 10.3390/polym8090326] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/18/2016] [Accepted: 08/29/2016] [Indexed: 11/16/2022] Open
Abstract
Recent research in the field of gecko-inspired dry adhesive has focused on modifying the material and structural properties of polymer-based nanohairs. Polymers such as polystyrene (PS), high-density polyethylene (HDPE), ultraviolet curable epoxy (SU-8), polyurethane acrylate (PUA), polycarbonate (PC), and polydimethyl siloxane (PDMS) can fulfill many mechanical property requirements, are easily tunable, and can be produced via large-scale fabrication. However, the fabrication process for tilted structure remains challenging. The tilted structure is a crucial factor in high-degree conformal contact, which facilitates high adhesion, low effective modulus, and directional adhesion properties. Recent studies have attempted to create a tilted structure by applying beam irradiation, mechanical and thermal stress, and magnetic fields. This review provides a comprehensive investigation into advanced strategies for producing tilted polymeric nanostructures and their potential applications in the near future.
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Affiliation(s)
- Hyeon Seong Im
- Center for Neuroscience Imaging Research (CNIR), Institute of Basic Science, Suwon 440-746, Korea.
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Korea.
| | - Jong Uk Kim
- Center for Neuroscience Imaging Research (CNIR), Institute of Basic Science, Suwon 440-746, Korea.
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Korea.
| | - Sungwon Han
- Department of Chemistry, Sungkyunkwan University (SKKU), Suwon 440-746, Korea.
| | - Tae-Il Kim
- Center for Neuroscience Imaging Research (CNIR), Institute of Basic Science, Suwon 440-746, Korea.
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Korea.
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82
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Brodoceanu D, Bauer CT, Kroner E, Arzt E, Kraus T. Hierarchical bioinspired adhesive surfaces-a review. BIOINSPIRATION & BIOMIMETICS 2016; 11:051001. [PMID: 27529743 DOI: 10.1088/1748-3190/11/5/051001] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The extraordinary adherence and climbing agility of geckos on rough surfaces has been attributed to the multiscale hierarchical structures on their feet. Hundreds of thousands of elastic hairs called setae, each of which split into several spatulae, create a large number of contact points that generate substantial adhesion through van der Waals interactions. The hierarchical architecture provides increased structural compliance on surfaces with roughness features ranging from micrometers to millimeters. We review synthetic adhesion surfaces that mimic the naturally occurring hierarchy with an emphasis on microfabrication strategies, material choice and the adhesive performance achieved.
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Affiliation(s)
- D Brodoceanu
- INM-Leibniz Institute for New Materials, Campus D2 2, D-66123, Saarbrücken, Germany
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83
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Fischer SC, Levy O, Kroner E, Hensel R, Karp JM, Arzt E. Bioinspired polydimethylsiloxane-based composites with high shear resistance against wet tissue. J Mech Behav Biomed Mater 2016; 61:87-95. [DOI: 10.1016/j.jmbbm.2016.01.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 01/18/2016] [Indexed: 11/25/2022]
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84
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Neubauer JW, Xue L, Erath J, Drotlef DM, Campo AD, Fery A. Monitoring the Contact Stress Distribution of Gecko-Inspired Adhesives Using Mechano-Sensitive Surface Coatings. ACS APPLIED MATERIALS & INTERFACES 2016; 8:17870-17877. [PMID: 27327111 DOI: 10.1021/acsami.6b05327] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The contact geometry of microstructured adhesive surfaces is of high relevance for adhesion enhancement. Theoretical considerations indicate that the stress distribution in the contact zone is crucial for the detachment mechanism, but direct experimental evidence is missing so far. In this work, we propose a method that allows, for the first time, the detection of local stresses at the contact area of biomimetic adhesive microstructures during contact formation, compression and detachment. We use a mechano-sensitive polymeric layer, which turns mechanical stresses into changes of fluorescence intensity. The biomimetic surface is brought into contact with this layer in a well-defined fashion using a microcontact printer, while the contact area is monitored with fluorescence microscopy in situ. Thus, changes in stress distribution across the contact area during compression and pull-off can be visualized with a lateral resolution of 1 μm. We apply this method to study the enhanced adhesive performance of T-shaped micropillars, compared to flat punch microstructures. We find significant differences in the stress distribution of the both differing contact geometries during pull-off. In particular, we find direct evidence for the suppression of crack nucleation at the edge of T-shaped pillars, which confirms theoretical models for the superior adhesive properties of these structures.
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Affiliation(s)
- Jens W Neubauer
- Leibniz-Institut für Polymerforschung Dresden e.V. , Hohe Str. 6, 01069 Dresden, Germany
- Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany
| | - Longjian Xue
- School of Power and Mechanical Engineering, Wuhan University , South Donghu Road 8, 430072 Wuhan, China
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Johann Erath
- Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany
| | - Dirk-M Drotlef
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Aránzazu Del Campo
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
- INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany
- Chemistry Department, Saarland University , 66123 Saarbrücken, Germany
| | - Andreas Fery
- Leibniz-Institut für Polymerforschung Dresden e.V. , Hohe Str. 6, 01069 Dresden, Germany
- Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany
- Cluster of Excellence Centre for Advancing Electronics Dresden (cfaed), Technische Universität Dresden , 01062 Dresden, Germany
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85
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Izadi H, Dogra N, Perreault F, Schwarz C, Simon S, Vanderlick TK. Removal of Particulate Contamination from Solid Surfaces Using Polymeric Micropillars. ACS APPLIED MATERIALS & INTERFACES 2016; 8:16967-16978. [PMID: 27101206 DOI: 10.1021/acsami.5b09154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This Research Article describes a novel method for removal of particulate contamination, loosely referred to as dust, from solid surfaces using polymeric micropillars. In this Research Article, we illustrate for the first time that polymeric microfibrils of controlled interfacial and geometrical properties can effectively remove micrometric and submicrometric contaminant particles from a solid surface without damaging the underlying substrate. Once these microfibrils are brought into contact with a contaminated surface, because of their their soft and flexible structure, they develop intimate contact with both the surface contaminants and the substrate. While these intrinsically nonsticky micropillars have minimal interfacial interactions with the substrate, we show that they produce strong interfacial interactions with the contaminant particles, granting the detachment of the particles from the surface upon retraction of the cleaning material. The origin and strength of the interfacial interactions at the interfaces between a contaminant particle and both the substrate and the cleaning materials are thoroughly discussed. Unlike flat substrates of the same material, using microfibrillar structures of controlled interfacial and geometrical properties also allows the elimination of the adsorbed particles from the contact interface. Here we demonstrate that by moving the adsorbed particles from the tip to the side of the fibrils and consequently removing them from the contact interface, polymeric microfibrils can clean all contaminant particles from the surface. The effects of the geometrical and interfacial properties of polymeric micropillars on removing the adsorbed particles from the tips of the pillars are fully discussed. This research is not only important in terms of introducing a novel method which can offer a new paradigm for thorough yet nondestructive cleaning of dust particles from solid surfaces, but also it is of fundamental significance for researchers with interests in exploiting the benefits offered by microstructured surfaces in development of interfacially active materials and devices.
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Affiliation(s)
- Hadi Izadi
- Department of Chemical and Environmental Engineering, Yale University , 10 Hillhouse Avenue, New Haven, Connecticut 06520, United States
| | - Navneet Dogra
- Department of Chemical and Environmental Engineering, Yale University , 10 Hillhouse Avenue, New Haven, Connecticut 06520, United States
| | - François Perreault
- Department of Chemical and Environmental Engineering, Yale University , 10 Hillhouse Avenue, New Haven, Connecticut 06520, United States
| | - Cynthia Schwarz
- Yale University Art Gallery, Yale University , 1111 Chapel Street, New Haven, Connecticut 06510, United States
| | - Stefan Simon
- Institute for the Preservation of Cultural Heritage, Yale University , 300 Heffernan Drive, West Haven, Connecticut 06516, United States
| | - T Kyle Vanderlick
- Department of Chemical and Environmental Engineering, Yale University , 10 Hillhouse Avenue, New Haven, Connecticut 06520, United States
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86
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Xue L, Pham JT, Iturri J, Del Campo A. Stick-Slip Friction of PDMS Surfaces for Bioinspired Adhesives. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:2428-35. [PMID: 26903477 DOI: 10.1021/acs.langmuir.6b00513] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Friction plays an important role in the adhesion of many climbing organisms, such as the gecko. During the shearing between two surfaces, periodic stick-slip behavior is often observed and may be critical to the adhesion of gecko setae and gecko-inspired adhesives. Here, we investigate the influence of short oligomers and pendent chains on the stick-slip friction of polydimethylsiloxane (PDMS), a commonly used material for bioinspired adhesives. Three different stick-slip patterns were observed on these surfaces (flat or microstructured) depending on the presence or absence of oligomers and their ability to diffuse out of the material. After washing samples to remove any untethered oligomeric chains, or after oxygen plasma treatment to convert the surface to a thin layer of silica, we decouple the contributions of stiffness, oligomers, and pendant chains to the stick-slip behavior. The stick phase is mainly controlled by the stiffness while the amount of untethered oligomers and pendant chains available at the contact interface defines the slip phase. A large amount of oligomers and pendant chains resulted in a large slip time, dominating the period of stick-slip motion.
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Affiliation(s)
- Longjian Xue
- School of Power and Mechanical Engineering, Wuhan University , South Donghu Road 8, 430072 Wuhan, China
- Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - Jonathan T Pham
- Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - Jagoba Iturri
- Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - Aránzazu Del Campo
- Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
- INM- Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany
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87
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Wang Y, Li X, Tian H, Hu H, Tian Y, Shao J, Ding Y. Rectangle-capped and tilted micropillar array for enhanced anisotropic anti-shearing in biomimetic adhesion. J R Soc Interface 2016; 12:rsif.2015.0090. [PMID: 25808338 DOI: 10.1098/rsif.2015.0090] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dry adhesion observed in the feet of various small creatures has attracted considerable attention owing to the unique advantages such as self-cleaning, adaptability to rough surfaces along with repeatable and reversible adhesiveness. Among these advantages, for practical applications, proper detachability is critical for dry adhesives with artificial microstructures. In this study, we present a microstructured array consisting of both asymmetric rectangle-capped tip and tilted shafts, which produce an orthogonal anisotropy of the shearing strength along the long and short dimensions of the tip, with a maximum anti-shearing in the two directions along the longer dimension. Meanwhile, the tilt feature can enhance anisotropic shearing adhesion by increasing shearing strength in the forward shearing direction and decreasing strength in the reverse shearing direction along the short dimension of the tip, leading to a minimum anti-shearing in only one of the two directions along the shorter dimension of the rectangular tip. Such a microstructured adhesive with only one weak shearing direction, leading to well-controlled attachment and detachment of the adhesive, is created in our experiment by conventional double-sided exposure of a photoresist followed by a moulding process.
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Affiliation(s)
- Yue Wang
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Xiangming 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
| | - Hong Hu
- Micro- and Nano-technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Yu Tian
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, 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
| | - Yucheng Ding
- 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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88
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Frost SJ, Mawad D, Hook J, Lauto A. Micro- and Nanostructured Biomaterials for Sutureless Tissue Repair. Adv Healthc Mater 2016; 5:401-14. [PMID: 26725593 DOI: 10.1002/adhm.201500589] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/23/2015] [Indexed: 01/01/2023]
Abstract
Sutureless procedures for wound repair and closure have recently integrated nanostructured devices to improve their effectiveness and clinical outcome. This review highlights the major advances in gecko-inspired bioadhesives that relies mostly on van der Waals bonding forces. These are challenged by the moist environment of surgical settings that weaken adherence to tissue. The incorporation of nanoparticles in biomatrices and their role in tissue repair and drug delivery is also reviewed with an emphasis on procedures involving adhesives that are laser-activated. Nanostructured adhesive devices have the advantage of being minimally invasive to tissue, can seal wounds, and deliver drugs in situ. All these tasks are very difficult to accomplish by sutures or staples that are invasive to host organs and often cause scarring.
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Affiliation(s)
- Samuel J. Frost
- School of Science and Health; University of Western Sydney; Penrith NSW 2751 Australia
| | - D. Mawad
- Department of Materials; Imperial College London; SW7 2AZ UK
- School of Materials Science and Engineering; University of New South Wales; Sydney 2052 Australia
| | - J. Hook
- School of Chemistry; University of New South Wales; Sydney 2052 Australia
| | - Antonio Lauto
- School of Science and Health; University of Western Sydney; Penrith NSW 2751 Australia
- The Biomedical Engineering and Neuroscience (BENS) Research Group; The MARCS Institute; Penrith NSW 2751 Australia
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89
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Gecko Adhesion. Biomimetics (Basel) 2016. [DOI: 10.1007/978-3-319-28284-8_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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90
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Labonte D, Federle W. Scaling and biomechanics of surface attachment in climbing animals. Philos Trans R Soc Lond B Biol Sci 2015; 370:20140027. [PMID: 25533088 PMCID: PMC4275900 DOI: 10.1098/rstb.2014.0027] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Attachment devices are essential adaptations for climbing animals and valuable models for synthetic adhesives. A major unresolved question for both natural and bioinspired attachment systems is how attachment performance depends on size. Here, we discuss how contact geometry and mode of detachment influence the scaling of attachment forces for claws and adhesive pads, and how allometric data on biological systems can yield insights into their mechanism of attachment. Larger animals are expected to attach less well to surfaces, due to their smaller surface-to-volume ratio, and because it becomes increasingly difficult to distribute load uniformly across large contact areas. In order to compensate for this decrease of weight-specific adhesion, large animals could evolve overproportionally large pads, or adaptations that increase attachment efficiency (adhesion or friction per unit contact area). Available data suggest that attachment pad area scales close to isometry within clades, but pad efficiency in some animals increases with size so that attachment performance is approximately size-independent. The mechanisms underlying this biologically important variation in pad efficiency are still unclear. We suggest that switching between stress concentration (easy detachment) and uniform load distribution (strong attachment) via shear forces is one of the key mechanisms enabling the dynamic control of adhesion during locomotion.
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Affiliation(s)
- David Labonte
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Walter Federle
- Department of Zoology, University of Cambridge, Cambridge, UK
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91
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Cho Y, Kim G, Cho Y, Lee SY, Minsky H, Turner KT, Gianola DS, Yang S. Orthogonal Control of Stability and Tunable Dry Adhesion by Tailoring the Shape of Tapered Nanopillar Arrays. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:7788-93. [PMID: 26488215 DOI: 10.1002/adma.201503347] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Revised: 08/25/2015] [Indexed: 05/06/2023]
Abstract
Tapered nanopillar structures of different cross-sectional geometries including cone-, pencil-like, and stepwise are prepared from anodized aluminum oxide templates. The shape effect on the adhesion strength is investigated in experiments and simulation. Cone-shaped nanopillars are highly bendable under load and can recover after unloading, thus, warranting high adhesion strength, 34 N cm(-2) . The pencil-like and stepwise nano-pillars are, however, easily fractured and are not recoverable under the same conditions.
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Affiliation(s)
- Younghyun Cho
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA
| | - Gyuseok Kim
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA
| | - Yigil Cho
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA
| | - Su Yeon Lee
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA
| | - Helen Minsky
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA, 19104, USA
| | - Kevin T Turner
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 220 South 33rd Street, Philadelphia, PA, 19104, USA
| | - Daniel S Gianola
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA
| | - Shu Yang
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA
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92
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Biswas S, Chakrabarti A, Chateauminois A, Wandersman E, Prevost AM, Chaudhury MK. Soft Lithography Using Nectar Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:13155-13164. [PMID: 26563988 DOI: 10.1021/acs.langmuir.5b03829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In spite of significant advances in replication technologies, methods to produce well-defined three-dimensional structures are still at its infancy. Such a limitation would be evident if we were to produce a large array of simple and, especially, compound convex lenses, also guaranteeing that their surfaces would be molecularly smooth. Here, we report a novel method to produce such structures by cloning the 3D shape of nectar drops, found widely in nature, using conventional soft lithography.The elementary process involves transfer of a thin patch of the sugar solution coated on a glass slide onto a hydrophobic substrate on which this patch evolves into a microdroplet. Upon the absorption of water vapor, such a microdroplet grows linearly with time, and its final size can be controlled by varying its exposure time to water vapor. At any stage of the evolution of the size of the drop, its shape can be cloned onto a soft elastomer by following the well-known methods of molding and cross-linking the same. A unique new science that emerges in our attempt to understand the transfer of the sugar patch and its evolution to a spherical drop is the elucidation of the mechanics underlying the contact of a deformable sphere against a solid support intervening a thin liquid film. A unique aspect of this work is to demonstrate that higher level structures can also be generated by transferring even smaller nucleation sites on the surface of the primary lenses and then allowing them to grow by absorption of water vapor. What results at the end is either a well-controlled distribution of smooth hemispherical lenses or compound structures that could have potential applications in the fundamental studies of contact mechanics, wettability, and even in optics.
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Affiliation(s)
- Saheli Biswas
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Aditi Chakrabarti
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Antoine Chateauminois
- Soft Matter Science and Engineering Laboratory (SIMM), CNRS/UPMC Univ Paris 6, UMR 7615, ESPCI, F-75005 Paris, France
| | - Elie Wandersman
- CNRS, Sorbonne Universités, UPMC Univ Paris 06, UMR 8237, Laboratoire Jean Perrin (LJP), F-75005, Paris, France
| | - Alexis M Prevost
- CNRS, Sorbonne Universités, UPMC Univ Paris 06, UMR 8237, Laboratoire Jean Perrin (LJP), F-75005, Paris, France
| | - Manoj K Chaudhury
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
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93
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Purtov J, Frensemeier M, Kroner E. Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives. ACS APPLIED MATERIALS & INTERFACES 2015; 7:24127-35. [PMID: 26457864 PMCID: PMC4642880 DOI: 10.1021/acsami.5b07287] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 10/12/2015] [Indexed: 05/26/2023]
Abstract
Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm(2) provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects.
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Affiliation(s)
- Julia Purtov
- Department
of Materials Science and Engineering, Saarland
University, Campus D2 2, 66123 Saarbrücken, Germany
- INM − Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - Mareike Frensemeier
- Department
of Materials Science and Engineering, Saarland
University, Campus D2 2, 66123 Saarbrücken, Germany
- INM − Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - Elmar Kroner
- INM − Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
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94
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Bauer CT, Kroner E, Fleck NA, Arzt E. Hierarchical macroscopic fibrillar adhesives: in situ study of buckling and adhesion mechanisms on wavy substrates. BIOINSPIRATION & BIOMIMETICS 2015; 10:066002. [PMID: 26496128 DOI: 10.1088/1748-3190/10/6/066002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Nature uses hierarchical fibrillar structures to mediate temporary adhesion to arbitrary substrates. Such structures provide high compliance such that the flat fibril tips can be better positioned with respect to asperities of a wavy rough substrate. We investigated the buckling and adhesion of hierarchically structured adhesives in contact with flat smooth, flat rough and wavy rough substrates. A macroscopic model for the structural adhesive was fabricated by molding polydimethylsiloxane into pillars of diameter in the range of 0.3-4.8 mm, with up to three different hierarchy levels. Both flat-ended and mushroom-shaped hierarchical samples buckled at preloads one quarter that of the single level structures. We explain this behavior by a change in the buckling mode; buckling leads to a loss of contact and diminishes adhesion. Our results indicate that hierarchical structures can have a strong influence on the degree of adhesion on both flat and wavy substrates. Strategies are discussed that achieve highly compliant substrates which adhere to rough substrates.
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Affiliation(s)
- Christina T Bauer
- INM-Leibniz Institute for New Materials, Campus D2 2, D-66123 Saarbrücken, Germany. Saarland University, Campus D2 2, D-66123 Saarbrücken, Germany
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95
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Miller DR, Das S, Huang KY, Han S, Israelachvili JN, Waite JH. Mussel Coating Protein-Derived Complex Coacervates Mitigate Frictional Surface Damage. ACS Biomater Sci Eng 2015; 1:1121-1128. [PMID: 26618194 PMCID: PMC4642218 DOI: 10.1021/acsbiomaterials.5b00252] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 09/14/2015] [Indexed: 12/01/2022]
Abstract
![]()
The role of friction in the functional
performance of biomaterial
interfaces is widely reckoned to be critical and complicated but poorly
understood. To better understand friction forces, we investigated
the natural adaptation of the holdfast or byssus of mussels that live
in high-energy surf habitats. As the outermost covering of the byssus,
the cuticle deserves particular attention for its adaptations to frictional
wear under shear. In this study, we coacervated one of three variants
of a key cuticular component, mussel foot protein 1, mfp-1 [(1) Mytilus californianus mcfp-1, (2) rmfp-1, and (3) rmfp-1-Dopa],
with hyaluronic acid (HA) and investigated the wear protection capabilities
of these coacervates to surfaces (mica) during shear. Native mcfp-1/HA
coacervates had an intermediate coefficient of friction (μ ∼0.3)
but conferred excellent wear protection to mica with no damage from
applied loads, F⊥, as high as 300
mN (pressure, P, > 2 MPa). Recombinant rmfp-1/HA
coacervates exhibited a comparable coefficient of friction (μ
∼0.3); however, wear protection was significantly inferior
(damage at F⊥ > 60 mN) compared
with that of native protein coacervates. Wear protection of rmfp-1/HA
coacervates increased 5-fold upon addition of the surface adhesive
group 3,4-dihydroxyphenylalanine, (Dopa). We propose a Dopa-dependent
wear protection mechanism to explain the differences in wear protection
between coacervates. Our results reveal a significant untapped potential
for coacervates in applications that require adhesion, lubrication,
and wear protection. These applications include artificial joints,
contact lenses, dental sealants, and hair and skin conditioners.
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Affiliation(s)
- Dusty Rose Miller
- Biomolecular Science and Engineering Program, University of California , Santa Barbara, California 93106-9611, United States
| | - Saurabh Das
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106-5080, United States
| | - Kuo-Ying Huang
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9625, United States
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9625, United States
| | - Jacob N Israelachvili
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106-5080, United States
| | - J Herbert Waite
- Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106-9625, United States
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96
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Das S, Cadirov N, Chary S, Kaufman Y, Hogan J, Turner KL, Israelachvili JN. Stick-slip friction of gecko-mimetic flaps on smooth and rough surfaces. J R Soc Interface 2015; 12:20141346. [PMID: 25589569 DOI: 10.1098/rsif.2014.1346] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The discovery and understanding of gecko 'frictional-adhesion' adhering and climbing mechanism has allowed researchers to mimic and create gecko-inspired adhesives. A few experimental and theoretical approaches have been taken to understand the effect of surface roughness on synthetic adhesive performance, and the implications of stick-slip friction during shearing. This work extends previous studies by using a modified surface forces apparatus to quantitatively measure and model frictional forces between arrays of polydimethylsiloxane gecko footpad-mimetic tilted microflaps against smooth and rough glass surfaces. Constant attachments and detachments occur between the surfaces during shearing, as described by an avalanche model. These detachments ultimately result in failure of the adhesion interface and have been characterized in this study. Stick-slip friction disappears with increasing velocity when the flaps are sheared against a smooth silica surface; however, stick-slip was always present at all velocities and loads tested when shearing the flaps against rough glass surfaces. These results demonstrate the significance of pre-load, shearing velocity, shearing distances, commensurability and shearing direction of gecko-mimetic adhesives and provide us a simple model for analysing and/or designing such systems.
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Affiliation(s)
- Saurabh Das
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Nicholas Cadirov
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Sathya Chary
- Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Yair Kaufman
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Jack Hogan
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Kimberly L Turner
- Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Jacob N Israelachvili
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
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97
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Marvi H, Song S, Sitti M. Experimental Investigation of Optimal Adhesion of Mushroomlike Elastomer Microfibrillar Adhesives. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:10119-10124. [PMID: 26322396 DOI: 10.1021/acs.langmuir.5b02415] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Optimal fiber designs for the maximal pull-off force have been indispensable for increasing the attachment performance of recently introduced gecko-inspired reversible micro/nanofibrillar adhesives. There are several theoretical studies on such optimal designs; however, due to the lack of three-dimensional (3D) fabrication techniques that can fabricate such optimal designs in 3D, there have not been many experimental investigations on this challenge. In this study, we benefitted from recent advances in two-photon lithography techniques to fabricate mushroomlike polyurethane elastomer fibers with different aspect ratios of tip to stalk diameter (β) and tip wedge angles (θ) to investigate the effect of these two parameters on the pull-off force. We found similar trends to those predicted theoretically. We found that β has an impact on the slope of the force-displacement curve while both β and θ play a role in the stress distribution and crack propagation. We found that these effects are coupled and the optimal set of parameters also depends on the fiber material. This is the first experimental verification of such optimal designs proposed for mushroomlike microfibers. This experimental approach could be used to evaluate a wide range of complex microstructured adhesive designs suggested in the literature and optimize them.
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Affiliation(s)
- Hamidreza Marvi
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Arizona State University , Tempe, Arizona 85287, United States
| | - Sukho Song
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Max-Planck Institute for Intelligent Systems , Stuttgart 70569, Germany
| | - Metin Sitti
- Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
- Max-Planck Institute for Intelligent Systems , Stuttgart 70569, Germany
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98
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Akerboom S, Appel J, Labonte D, Federle W, Sprakel J, Kamperman M. Enhanced adhesion of bioinspired nanopatterned elastomers via colloidal surface assembly. J R Soc Interface 2015; 12:20141061. [PMID: 25392404 DOI: 10.1098/rsif.2014.1061] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloidal lithography. Close-packed monolayers of polystyrene particles were formed at the air/water interface, on which polydimethylsiloxane (PDMS) was applied. The order of the colloidal monolayer and the immersion depth of the particles were tuned by altering the pH and ionic strength of the water. Initially, PDMS completely wetted the air/water interface outside the monolayer, thereby compressing the monolayer as in a Langmuir trough; further application of PDMS subsequently covered the colloidal monolayers. PDMS curing and particle extraction resulted in elastomers patterned with nanodimples. Adhesion and friction of these nanopatterned surfaces with varying dimple depth were studied using a spherical probe as a counter-surface. Compared with smooth surfaces, adhesion of nanopatterned surfaces was enhanced, which is attributed to an energy-dissipating mechanism during pull-off. All nanopatterned surfaces showed a significant decrease in friction compared with smooth surfaces.
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Affiliation(s)
- Sabine Akerboom
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands
| | - Jeroen Appel
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands
| | - David Labonte
- Insect Biomechanics Workgroup, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Walter Federle
- Insect Biomechanics Workgroup, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Joris Sprakel
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands
| | - Marleen Kamperman
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands
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99
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Wasay A, Sameoto D. Gecko gaskets for self-sealing and high-strength reversible bonding of microfluidics. LAB ON A CHIP 2015; 15:2749-2753. [PMID: 26016928 DOI: 10.1039/c5lc00342c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report in this work a novel reversible bonding technique for elastomeric microfluidic devices by integrating gecko-inspired dry adhesives with microfluidic channels which greatly enhances the bonding strength of reversibly sealed channels. The concept is applicable to nearly any elastomer and can be used to bond against any smooth surface which allows for van der Waals interactions. It does not require any solvents or glues or sources for plasma activation or thermal-compressive loading to aid the bonding process and is achievable at zero extra cost. We also demonstrate a quick fabrication technique involving soft master thermo-compressive molding of these microfluidic devices with thermoplastic elastomers. The resultant devices can be used for both pressure driven and non-pressure driven flows. We report the maximum contained pressure of these devices manufactured from two grades of styrene ethylene butylene styrene (SEBS) by conducting a burst pressure test with various substrates.
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Affiliation(s)
- A Wasay
- Mechanical Engineering Department, University of Alberta, Edmonton, Alberta T6G 2R3, Canada.
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100
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Chaudhary OJ, Calius EP, Kennedy JV, Dickinson M, Loho T, Travas-Sejdic J. Bioinspired dry adhesive: Poly(dimethylsiloxane) grafted with poly(2-ethylhexyl acrylate) brushes. Eur Polym J 2015. [DOI: 10.1016/j.eurpolymj.2015.05.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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