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Kajouri R, Theodorakis PE, Milchev A. Durotaxis and Antidurotaxis Droplet Motion onto Gradient Gel-Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:17779-17785. [PMID: 39106075 PMCID: PMC11340025 DOI: 10.1021/acs.langmuir.4c02257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2024] [Revised: 07/23/2024] [Accepted: 07/23/2024] [Indexed: 08/07/2024]
Abstract
The self-sustained motion of fluids on gradient substrates is a spectacular phenomenon, which can be employed and controlled in applications by carefully engineering the substrate properties. Here, we report on a design of a gel substrate with stiffness gradient, which can cause the spontaneous motion of a droplet along (durotaxis) or to the opposite (antidurotaxis) direction of the gradient, depending on the droplet affinity to the substrate. By using extensive molecular dynamics simulations of a coarse-grained model, we find that the mechanisms of the durotaxis and antidurotaxis droplet motion are distinct, require the minimization of the interfacial energy between the droplet and the substrate, and share similarities with those mechanisms previously observed for brush substrates with stiffness gradient. Moreover, durotaxis motion takes place over a wider range of affinities and is generally more efficient (faster motion) than antidurotaxis. Thus, our study points to further possibilities and guidelines for realizing both antidurotaxis and durotaxis motion on the same gradient substrate for applications in microfluidics, energy conservation, and biology.
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Affiliation(s)
- Russell Kajouri
- Institute
for Computational Physics, University of
Stuttgart, 70569 Stuttgart, Germany
| | | | - Andrey Milchev
- Bulgarian
Academy of Sciences, Institute of Physical
Chemistry, 1113 Sofia, Bulgaria
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2
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Kajouri R, Theodorakis PE, Židek J, Milchev A. Antidurotaxis Droplet Motion onto Gradient Brush Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:15285-15296. [PMID: 37672007 PMCID: PMC10621003 DOI: 10.1021/acs.langmuir.3c01999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 08/28/2023] [Indexed: 09/07/2023]
Abstract
Durotaxis motion is a spectacular phenomenon manifesting itself by the autonomous motion of a nano-object between parts of a substrate with different stiffness. This motion usually takes place along a stiffness gradient from softer to stiffer parts of the substrate. Here, we propose a new design of a polymer brush substrate that demonstrates antidurotaxis droplet motion, that is, droplet motion from stiffer to softer parts of the substrate. By carrying out extensive molecular dynamics simulation of a coarse-grained model, we find that antidurotaxis is solely controlled by the gradient in the grafting density of the brush and is favorable for fluids with a strong attraction to the substrate (low surface energy). The driving force of the antidurotaxial motion is the minimization of the droplet-substrate interfacial energy, which is attributed to the penetration of the droplet into the brush. Thus, we anticipate that the proposed substrate design offers a new understanding and possibilities in the area of autonomous motion of droplets for applications in microfluidics, energy conservation, and biology.
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Affiliation(s)
- Russell Kajouri
- Institute
of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | | | - Jan Židek
- Central
European Institute of Technology, Brno University
of Technology, Purkyňova
656/123, 612 00 Brno, Czech Republic
| | - Andrey Milchev
- Bulgarian
Academy of Sciences, Institute of Physical Chemistry, 1113 Sofia, Bulgaria
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3
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Liu W, Lu Y, Shen Y, Chen H, Ni Y, Xu Y. Spontaneous Transport Mechanics of Water Droplets under a Synergistic Action of Designed Pattern and Non-Wetting Gradient. ACS OMEGA 2023; 8:16450-16458. [PMID: 37179628 PMCID: PMC10173426 DOI: 10.1021/acsomega.3c01536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 04/18/2023] [Indexed: 05/15/2023]
Abstract
The controllable spontaneous transport of water droplets on solid surfaces has a broad application background in daily life. Herein, a patterned surface with two different non-wetting characteristics was developed to control the droplet transport behavior. Consequently, the patterned surface exhibited great water-repellant properties in the superhydrophobic region, and the water contact angle reached 160° ± 0.2°. Meanwhile, the water contact angle on the wedge-shaped hydrophilic region dropped to 22° after UV irradiation treatment. On this basis, the maximum transport distance of water droplets could be observed on the sample surface with a small wedge angle of 5° (10.62 mm), and the maximum average transport velocity of droplets was obtained on the sample surface with a large wedge angle of 10° (218.01 mm/s). In terms of spontaneous droplet transport on an inclined surface (4°), both the 8 μL droplet and 50 μL droplet could move upward against gravity, which showed that the sample surface possessed an obvious driving force for droplet transport. Surface non-wetting gradient and the wedge-shaped pattern provided unbalanced surface tension to produce the driving forces in the process of droplet transport, and the Laplace pressure as well is produced inside the water droplet during this process. This work provides a new strategy to develop a patterned superhydrophobic surface for droplet transport.
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Affiliation(s)
- Weilan Liu
- Institute
of Advanced Materials (IAM), College of Materials Science and Engineering, Nanjing Tech University, 30 Puzhu South Road, Nanjing 211816, P. R. China
| | - Yang Lu
- Institute
of Advanced Materials (IAM), College of Materials Science and Engineering, Nanjing Tech University, 30 Puzhu South Road, Nanjing 211816, P. R. China
- College
of Materials Science and Technology, Nanjing
University of Aeronautics and Astronautics, Nanjing 211100, P. R. China
| | - Yizhou Shen
- Institute
of Advanced Materials (IAM), College of Materials Science and Engineering, Nanjing Tech University, 30 Puzhu South Road, Nanjing 211816, P. R. China
- College
of Materials Science and Technology, Nanjing
University of Aeronautics and Astronautics, Nanjing 211100, P. R. China
- . Phone: +86 25 52112911
| | - Haifeng Chen
- Department
of Materials Chemistry, Qiuzhen School, Huzhou University, 759#
East 2nd Road, Huzhou 313000, P. R. China
| | - Yaru Ni
- Institute
of Advanced Materials (IAM), College of Materials Science and Engineering, Nanjing Tech University, 30 Puzhu South Road, Nanjing 211816, P. R. China
- . Phone: +86 25 83587220
| | - Yangjiangshan Xu
- College
of Materials Science and Technology, Nanjing
University of Aeronautics and Astronautics, Nanjing 211100, P. R. China
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4
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Kajouri R, Theodorakis PE, Deuar P, Bennacer R, Židek J, Egorov SA, Milchev A. Unidirectional Droplet Propulsion onto Gradient Brushes without External Energy Supply. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:2818-2828. [PMID: 36758225 PMCID: PMC9948540 DOI: 10.1021/acs.langmuir.2c03381] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/27/2023] [Indexed: 06/18/2023]
Abstract
Using extensive molecular dynamics simulation of a coarse-grained model, we demonstrate the possibility of sustained unidirectional motion (durotaxis) of droplets without external energy supply when placed on a polymer brush substrate with stiffness gradient in a certain direction. The governing key parameters for the specific substrate design studied, which determine the durotaxis efficiency, are found to be the grafting density of the brush and the droplet adhesion to the brush surface, whereas the strength of the stiffness gradient, the viscosity of the droplet, or the length of the polymer chains of the brush have only a minor effect on the process. It is shown that this durotaxial motion is driven by the steady increase of the interfacial energy between droplet and brush as the droplet moves from softer to stiffer parts of the substrate whereby the mean driving force gradually declines with decreasing roughness of the brush surface. We anticipate that our findings indicate further possibilities in the area of nanoscale motion without external energy supply.
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Affiliation(s)
- Russell Kajouri
- Institute
of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | | | - Piotr Deuar
- Institute
of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Rachid Bennacer
- Université
Paris-Saclay, ENS Paris-Saclay, CNRS, LMPS, 4 Av. des Sciences, 91190 Gif-sur-Yvette, France
| | - Jan Židek
- Central
European Institute of Technology, Brno University
of Technology, Purkyňova
656/123, 612 00 Brno, Czech Republic
| | - Sergei A. Egorov
- Department
of Chemistry, University of Virginia, 22901 Charlottesville, Virginia, United States
- Institut
für Physik, Johannes Gutenberg Universität
Mainz, 55099 Mainz, Germany
- Leibniz-Institut
für Polymerforschung, Institut Theorie
der Polymere, Hohe Str.
6, 01069 Dresden, Germany
| | - Andrey Milchev
- Bulgarian
Academy of Sciences, Institute of Physical
Chemistry, 1113 Sofia, Bulgaria
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5
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Investigation on the Anisotropic Wetting Properties of Water Droplets on Bio-Inspired Groove Structures Fabricated by 3D Printing and Surface Modifications. Biomimetics (Basel) 2022; 7:biomimetics7040174. [PMID: 36412702 PMCID: PMC9680309 DOI: 10.3390/biomimetics7040174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 10/16/2022] [Accepted: 10/22/2022] [Indexed: 12/14/2022] Open
Abstract
The self-driving structure to orientate the water movement has attracted considerable attention. Inspired by the wedgelike structures of biological materials in nature, such as spider silks and cactus spines, anisotropic spreading can be realized by combining Laplace pressure gradient and hydrophilic surface. In this study, a series of groove patterns were fabricated by a combination of 3D printing and surface modification. PLA pattern was modified by the atmospheric pressure plasma, followed by grafting with hydrolyzed APTES. This work reports the anisotropic transport of water droplets on a series of designed dart-shaped groove patterns with specific angles in the main arrow and tail regions. This structure can induce capillary force to regulate droplets from the main cone to two wedgelike, whereas the droplets are hindered toward the opposite side is oat the vicinity of the groove's tail. By means of the experiment, the mechanism of water transport in this pattern was revealed. This study can contribute a potential approach to manipulate and apply anisotropic wetting in many fields.
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6
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Gulfam R, Chen Y. Recent Growth of Wettability Gradient Surfaces: A Review. Research (Wash D C) 2022; 2022:9873075. [PMID: 35935132 PMCID: PMC9327586 DOI: 10.34133/2022/9873075] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 06/01/2022] [Indexed: 11/06/2022] Open
Abstract
This review reports the recent progress and future prospects of wettability gradient surfaces (WGSs), particularly focusing on the governing principles, fabrication methods, classification, characterization, and applications. While transforming the inherent wettability into artificial wettability via bioinspiration, topographic micro/nanostructures are produced with changed surface energy, resulting in new droplet wetting regimes and droplet dynamic regimes. WGSs have been mainly classified in dry and wet surfaces, depending on the apparent surface states. Wettability gradient has long been documented as a surface phenomenon inducing the droplet mobility in the direction of decreasing wettability. However, it is herein critically emphasized that the wettability gradient does not always result in droplet mobility. Indeed, the sticky and slippery dynamic regimes exist in WGSs, prohibiting or allowing the droplet mobility, respectively. Lastly, the stringent bottlenecks encountered by WGSs are highlighted along with solution-oriented recommendations, and furthermore, phase change materials are strongly anticipated as a new class in WGSs. In all, WGSs intend to open up new technological insights for applications, encompassing water harvesting, droplet and bubble manipulation, controllable microfluidic systems, and condensation heat transfer, among others.
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Affiliation(s)
- Raza Gulfam
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yongping Chen
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China
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7
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Lv F, Zhao F, Cheng D, Dong Z, Jia H, Xiao X, Orejon D. Bioinspired functional SLIPSs and wettability gradient surfaces and their synergistic cooperation and opportunities for enhanced condensate and fluid transport. Adv Colloid Interface Sci 2022; 299:102564. [PMID: 34861513 DOI: 10.1016/j.cis.2021.102564] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/15/2021] [Accepted: 11/15/2021] [Indexed: 01/16/2023]
Abstract
Bioinspired smart functional surfaces have received increasing attention in recent years owed to their tunable wettability and enhanced droplet transport suggesting them as excellent candidates for industrial and nanotechnology-related applications. More specifically, bioinspired slippery lubricant infused porous surfaces (SLIPSs) have been proposed for their low adhesion enabling continuous dropwise condensation (DWC) even of low-surface tension fluids. In addition, functional surfaces with chemical and/or structural wettability gradients have also been exploited empowering spontaneous droplet transport in a controlled manner. Current research has focused on the better understanding of the mechanisms and intimate interactions taking place between liquid droplets and functional surfaces or on the forces imposed by differences in surface wettability and/or by Laplace pressure owed to chemical or structural gradients. Nonetheless, less attention has been paid to the synergistic cooperation of efficiently driving droplet transport via chemical and/or structural patterns/gradients on a low surface energy/adhesion background imposed by SLIPSs, with the consequent promising potential for microfluidics and condensation heat transfer applications amongst others. This review provides a detailed and timely overview and summary on recent advances and developments on bioinspired SLIPSs and on wettability gradient surfaces with focus on their synergistic cooperation for condensation and fluid transport related applications. Firstly, the fundamental theory and mechanisms governing complex droplet transport on homogeneous, on wettability gradient surfaces and on inclined SLIPSs are introduced. Secondly, recent advances on the fabrication and characterization of SLIPSs and functional surfaces are presented. Then, the condensation performance on such functional surfaces comprising chemical or structural wettability gradients is reviewed and their applications on condensation heat transfer are summarized. Last a summary outlook highlighting the opportunities and challenges on the synergistic cooperation of SLIPSs and wettability gradient surfaces for heat transfer as well as future perspective in modern applications are presented.
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8
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Huang J, Hao H, Huang Y, Yu B, Ren K, Jin Q, Ji J. Gradient Porous Structure Templated by Breath Figure Method. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:6016-6021. [PMID: 33951392 DOI: 10.1021/acs.langmuir.1c00636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Surfaces with gradient topography are important in various fields but are difficult to fabricate. Herein, we report a facile and robust way to fabricate a surface with gradient topography of porous structure, in one direction, based on the breath figure (BF) method for the first time. The influencing factors including relative humidity (RH), sample immersion time, and solvent composition, affecting the speed, time, and model of the droplet growth, respectively, were investigated to control gradient BF pores with different ranges of pore sizes. Applying appropriate parameters, gradient BF pores with a diameter difference over 400% were prepared on one sample. The mechanism of gradient duration of solvent evaporation at different regions of a sample for fabricating gradient pores was proposed and experimentally verified with recording optical and thermographic changes of the sample in the BF procedure. This new method provides a novel site for gradient topography fabrication.
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Affiliation(s)
- Junjie Huang
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Hongye Hao
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Yue Huang
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Bo Yu
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Kefeng Ren
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Qiao Jin
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Jian Ji
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
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9
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Chen X, Li X, Zuo P, Liang M, Li X, Xu C, Yuan Y, Wang S. Three-Dimensional Maskless Fabrication of Bionic Unidirectional Liquid Spreading Surfaces Using a Phase Spatially Shaped Femtosecond Laser. ACS APPLIED MATERIALS & INTERFACES 2021; 13:13781-13791. [PMID: 33703880 DOI: 10.1021/acsami.0c22080] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ubiquitous biological processes exhibit the ability to achieve spontaneous directionally guided droplet transport. Maskless three-dimensional (3D) fabrication of various miniature bionic structures, a method applicable to various materials, is subject to processing method limitations. This remains a large obstacle to realizing self-driven, continuous, and controllable unidirectional liquid spreading. Thus, we present a flexible maskless 3D method for fabricating bionic unidirectional liquid spreading surfaces by using a phase spatially shaped femtosecond laser. The laser can be transformed from having Gaussian distributions to having 3D bionic structure field distributions. Furthermore, we fabricated Syntrichia caninervis bionic structures with a spiculate end for unidirectional water spreading; 1 μL droplets had a 16 mm flow length on Si surfaces when the S. caninervis single structure was 34 (length), 8 (width), and 12 μm (height). Furthermore, various bionic structures-Nepenthes, cactus, and moth structures-were fabricated on Si, SiO2, and Ti. We also demonstrated the measurability of two-dimensional (S-shaped) curved flows on Si wafers as well as 3D curved flows on a Ti pipe turning 120° within 2320 ms. Our method can realize high-efficiency maskless 3D processing of various materials and structures (especially asymmetric structures); it is both flexible and fast, effectively expanding the processing capacity of micro-/nanostructures on patterned surfaces. This is of great significance to various domains such as microfluids, fog collection, and chemical reaction control.
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Affiliation(s)
- Xiaozhe Chen
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Xin Li
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Pei Zuo
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - MiSheng Liang
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Xiaojie Li
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Chenyang Xu
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Yongjiu Yuan
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
| | - Sumei Wang
- Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
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10
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Stable Superhydrophobic Aluminum Surfaces Based on Laser-Fabricated Hierarchical Textures. MATERIALS 2021; 14:ma14010184. [PMID: 33401702 PMCID: PMC7795392 DOI: 10.3390/ma14010184] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 12/23/2020] [Accepted: 12/28/2020] [Indexed: 01/28/2023]
Abstract
Laser-microtextured surfaces have gained an increasing interest due to their enormous spectrum of applications and industrial scalability. Direct laser interference patterning (DLIP) and the well-established direct laser writing (DLW) methods are suitable as a powerful combination for the fabrication of single (DLW or DLIP) and multi-scale (DLW+DLIP) textures. In this work, four-beam DLIP and DLW were used independently and combined to produce functional textures on aluminum. The influence of the laser processing parameters, such as the applied laser fluence and the number of pulses, on the resulting topography was analyzed by confocal microscopy and scanning electron microscopy. The static long-term and dynamic wettability characteristics of the laser-textured surfaces were determined through water contact angle and hysteresis measurements, revealing superhydrophobic properties with static contact angles up to 163° and hysteresis as low as 9°. The classical Cassie–Baxter and Wenzel models were applied, permitting a deeper understanding of the observed wetting behaviors. Finally, mechanical stability tests revealed that the DLW elements in the multi-scale structure protects the smaller DLIP features under tribological conditions.
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11
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Min S, Li S, Zhu Z, Li W, Tang X, Liang C, Wang L, Cheng X, Li WD. Gradient wettability induced by deterministically patterned nanostructures. MICROSYSTEMS & NANOENGINEERING 2020; 6:106. [PMID: 34567715 PMCID: PMC8433471 DOI: 10.1038/s41378-020-00215-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 08/24/2020] [Accepted: 09/10/2020] [Indexed: 06/12/2023]
Abstract
We report a large-scale surface with continuously varying wettability induced by ordered gradient nanostructures. The gradient pattern is generated from nonuniform interference lithography by utilizing the Gaussian-shaped intensity distribution of two coherent laser beams. We also develop a facile fabrication method to directly transfer a photoresist pattern into an ultraviolet (UV)-cured high-strength replication molding material, which eliminates the need for high-cost reactive ion etching and e-beam evaporation during the mold fabrication process. This facile mold is then used for the reproducible production of surfaces with gradient wettability using thermal-nanoimprint lithography (NIL). In addition, the wetting behavior of water droplets on the surface with the gradient nanostructures and therefore gradient wettability is investigated. A hybrid wetting model is proposed and theoretically captures the contact angle measurement results, shedding light on the wetting behavior of a liquid on structures patterned at the nanoscale.
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Affiliation(s)
- Siyi Min
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518052 China
| | - Shijie Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
| | - Zhouyang Zhu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
| | - Wei Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
| | - Xin Tang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
| | - Chuwei Liang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
- HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), Hangzhou, 311305 Zhejiang China
| | - Xing Cheng
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518052 China
| | - Wen-Di Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077 China
- HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), Hangzhou, 311305 Zhejiang China
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12
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Soltani M, Golovin K. Anisotropy-induced directional self-transportation of low surface tension liquids: a review. RSC Adv 2020; 10:40569-40581. [PMID: 35520851 PMCID: PMC9057580 DOI: 10.1039/d0ra08627d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 11/02/2020] [Indexed: 11/29/2022] Open
Abstract
Inspired by natural surfaces such as butterfly wings, cactus leaves, or the Nepenthes alata plant, synthetic materials may be engineered to directionally transport liquids on their surface without external energy input. This advantageous feature has been adopted for various mechanical and chemical processes, e.g. fog harvesting, lubrication, lossless chemical reactions, etc. Many studies have focused on the manipulation and transport of water or aqueous droplets, but significantly fewer have extended their work to low surface tension (LST) liquids, although these fluids are involved in numerous industrial and everyday processes. LST liquids completely wet most surfaces which makes spontaneous transportation an active challenge. This review focuses on recently developed strategies for passively and directionally transporting LST liquids.
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Affiliation(s)
- Mohammad Soltani
- Okanagan Polymer Engineering Research & Applications Laboratory, Faculty of Applied Science, University of British Columbia Canada
| | - Kevin Golovin
- Okanagan Polymer Engineering Research & Applications Laboratory, Faculty of Applied Science, University of British Columbia Canada
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13
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Stamatopoulos C, Milionis A, Ackerl N, Donati M, Leudet de la Vallée P, Rudolf von Rohr P, Poulikakos D. Droplet Self-Propulsion on Superhydrophobic Microtracks. ACS NANO 2020; 14:12895-12904. [PMID: 32806052 DOI: 10.1021/acsnano.0c03849] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Liquid transport (continuous or segmented) in microfluidic platforms typically requires pumping devices or external fields working collaboratively with special fluid properties to enable fluid motion. Natural liquid adhesion on surfaces deters motion and promotes the possibility of liquid or surface contamination. Despite progress, significant advancements are needed before devices for passive liquid propulsion, without the input of external energy and unwanted contamination, become a reality in applications. Here we present an unexplored and facile approach based on the Laplace pressure imbalance, manifesting itself through targeted track texturing, driving passively droplet motion, while maintaining the limited contact of the Cassie-Baxter state on superhydrophobic surfaces. The track topography resembles out-of-plane, backgammon-board, slowly converging microridges decorated with nanotexturing. This design naturally deforms asymmetrically the menisci formed at the bottom of a droplet contacting such tracks and causes a Laplace pressure imbalance that drives droplet motion. We investigate this effect over a range of opening track angles and develop a model to explain and quantify the underlying mechanism of droplet self-propulsion. We further implement the developed topography for applications relevant to microfluidic platform functionalities. We demonstrate control of the rebound angle of vertically impacting droplets, achieve horizontal self-transport to distances up to 65 times the droplet diameter, show significant uphill motion against gravity, and illustrate a self-driven droplet-merging process.
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14
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Shi D, Chen Y, Yao Y, Hou M, Chen X, Gao J, He Y, Zhang G, Wong CP. Ladderlike Conical Micropillars Facilitating Underwater Gas-Bubble Manipulation in an Aqueous Environment. ACS APPLIED MATERIALS & INTERFACES 2020; 12:42437-42445. [PMID: 32840997 DOI: 10.1021/acsami.0c13631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Underwater gas-bubble manipulation in aqueous environments is of great importance in industry and academia. Although the underwater gas bubble has been proved to be directionally transportable by various structures, transporting gas bubbles in 3D space remains a challenge. In this research, two kinds of tapered pillars, that is, ladderlike and helical ladderlike, were proposed for manipulating gas bubbles. To fabricate such unique structures, an improved alternative coating and etching method was developed. To meet the requirements of underwater gas-bubble transport, a modified gas-bubble slippery technology was also developed to enhance the aerophilic ability. The dynamics of the gas bubble was analyzed using a high-speed camera. The Laplace force that resulted from the geometry gradient was found to play a significant role in tuning the gas-bubble velocity. Through adjustments on the wettability, tilt angle, and geometry of each section of the tapered pillar, tuning the transport velocity from 113.9 ± 10.3 to 309.1 ± 5.8 mm/s becomes possible. On the basis of these findings, the helical ladderlike tapered pillar was fabricated and demonstrated to be able to transport gas bubbles in 3D space. These results may provide a new and systematic way to design and fabricate materials and structures for directional gas-bubble transport in 3D space.
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Affiliation(s)
- Dachuang Shi
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
| | - Yun Chen
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
- School of Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Yao Yao
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
| | - Maoxiang Hou
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
| | - Xin Chen
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
| | - Jian Gao
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
| | - Yunbo He
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
| | - Guoping Zhang
- The Shenzhen International Innovation Institutes of Advanced Electronic Materials, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Ching-Ping Wong
- School of Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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15
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Zuo Y, Zheng L, Zhao C, Liu H. Micro-/Nanostructured Interface for Liquid Manipulation and Its Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1903849. [PMID: 31482672 DOI: 10.1002/smll.201903849] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 08/12/2019] [Indexed: 05/09/2023]
Abstract
Understanding the relationship between liquid manipulation and micro-/nanostructured interfaces has gained much attention due to the wide potential applications in many fields, such as chemical and biomedical assays, environmental protection, industry, and even daily life. Much work has been done to construct various materials with interfacial liquid manipulation abilities, leading to a range of interesting applications. Herein, different fabrication methods from the top-down approach to the bottom-up approach and subsequent surface modifications of micro-/nanostructured interfaces are first introduced. Then, interactions between the surface and liquid, including liquid wetting, liquid transportation, and a number of corresponding models, together with the definition of hydrophilic/hydrophobic, oleophilic/olephobic, the definition and mechanism of superwetting, including superhydrophobicity, superhydrophilicity, and superoleophobicity, are presented. The micro-/nanostructured interface, with major applications in self-cleaning, antifogging, anti-icing, anticorrosion, drag-reduction, oil-water separation, water collection, droplet (micro)array, and surface-directed liquid transport, is summarized, and the mechanisms underlying each application are discussed. Finally, the remaining challenges and future perspectives in this area are included.
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Affiliation(s)
- Yinxiu Zuo
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Liuzheng Zheng
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Chao Zhao
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Hong Liu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
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16
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Cui M, Mu P, Shen Y, Zhu G, Luo L, Li J. Three-dimensional attapulgite with sandwich-like architecture used for multifunctional water remediation. Sep Purif Technol 2020. [DOI: 10.1016/j.seppur.2019.116210] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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17
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Wu H, Jiang K, Xu Z, Yu S, Peng X, Zhang Z, Bai H, Liu A, Chai G. Theoretical and Experimental Studies on the Controllable Pancake Bouncing Behavior of Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:17000-17008. [PMID: 31786923 DOI: 10.1021/acs.langmuir.9b03153] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A droplet that impacts on a superhydrophobic surface will undergo a process of unfolding, contracting, and finally rebounding from the surface. With regards to the pancake bouncing behavior of a droplet, since the retraction process of the droplet is omitted, the contact time is greatly shortened compared to the normal type of bouncing. However, the quantitative prediction to the range of droplet pancake bouncing and the adjustment of pancake bouncing state have yet to be probed into. In this paper, we reported the controllable pancake bouncing of droplets by adjusting the size of the superhydrophobic surface with microstructures. In addition, we also discovered a dimensional effect with regards to pancake bouncing, namely, the pancake bouncing would be more likely to happen on the surfaces with large post spacing for the droplet with the larger radius. The contact time could be reduced to 2 ms by adjusting the size of the microstructures and the radius of the droplets. Based on the relationship between the droplet bouncing state and the surface microstructure size, we are able to propose reasonable dimensions for the surfaces in order to control pancake bouncing.
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Affiliation(s)
- Huaping Wu
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
| | - Kunpeng Jiang
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
| | - Zhenxiong Xu
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
| | - Sihang Yu
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
| | - Xiang Peng
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
| | - Zheng Zhang
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
| | - Hao Bai
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Aiping Liu
- Center for Optoelectronics Materials and Devices , Zhejiang Sci-Tech University , Hangzhou 310018 , China
| | - Guozhong Chai
- Key Laboratory of E&M , Zhejiang University of Technology, Ministry of Education & Zhejiang Province , Hangzhou 310014 , China
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18
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Wu H, Yu S, Xu Z, Cao B, Peng X, Zhang Z, Chai G, Liu A. Theoretical and Experimental Study of Reversible and Stable Wetting States of a Hierarchically Wrinkled Surface Tuned by Mechanical Strain. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:6870-6877. [PMID: 31042869 DOI: 10.1021/acs.langmuir.9b00599] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The wetting behavior of hierarchically wrinkled surfaces has attracted great interest because of its broad application in flexible electronic, microfluidic chip, and biomedicine. However, theoretical studies concerning the relationship between the apparent contact angle and mechanical strain applied on the soft and flexible surface with a hierarchically wrinkled structure are still limited. We established a theoretical framework to describe and understand how prestrain and applied dynamic strain reversibly tune the wettability of the hierarchically wrinkled surface. More specifically, a direct relationship between the mechanical strain and contact angle was built through reversible tuning of the amplitude and the wavelength of the wrinkled structures caused by mechanical strain, which allowed for more precise adjustment of surface wettability. To verify the accuracy of the theoretical relationship between the contact angle and mechanical strain, a soft surface with a hierarchically wrinkled structure was prepared by combining wrinkled microstructures and strip ones. The results showed that the experimental contact angles were in agreement with the theoretical ones within a limited error range. This will be helpful for further investigation on the wettability of hierarchically wrinkled surfaces.
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Affiliation(s)
- Huaping Wu
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Sihang Yu
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Zhenxiong Xu
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Binbin Cao
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Xiang Peng
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Zheng Zhang
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Guozhong Chai
- Key Laboratory of E&M, Ministry of Education & Zhejiang Province , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Aiping Liu
- Center for Optoelectronics Materials and Devices , Zhejiang Sci-Tech University , Hangzhou 310018 , China
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19
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Liang L, Wang W, Chen J, Jiang K, Sheng Y, Peng X, Liu A, Wu H. Continuous Directional Water Delivery on the 3D-Printed Arrowhead Microstructure Array. MATERIALS 2019; 12:ma12071043. [PMID: 30934906 PMCID: PMC6480226 DOI: 10.3390/ma12071043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 11/16/2022]
Abstract
Unidirectional transport is attracting increasing attention in the field of microfluidics, because it does not require an external energy supply. However, most of the current self-driving structures are still plagued with persistent problems that restrict their practical applications. These include low transport velocity, short transport distance, and complex structure. This work reports the design of a new arrowhead microstructure array, on which liquid transport can reach speeds of 23 mm/s and the ratio of transport length to channel width (L/R) can reach up to approximately 40. This structure drives liquid through a unique arrow conformation, which can induce capillary force and arrest the reverse motion of the liquid simultaneously. By means of theory, simulation, and experiment, we have studied the mechanism of liquid transport on this structure. We provide a detailed discussion of the relationship between the velocity of liquid transport and the microstructural dimensions. The findings may inspire the design of novel, unidirectional, liquid-spreading surfaces.
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Affiliation(s)
- Lihua Liang
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
| | - Wei Wang
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
| | - Junjun Chen
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
| | - Kunpeng Jiang
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
| | - Yufeng Sheng
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
| | - Xiang Peng
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
| | - Aiping Liu
- Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018, China.
| | - Huaping Wu
- Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
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20
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Lu C, Shi F, Jin J, Peng X. Study on the Properties of Vertical Carbon Nanotube Films Grown on Stainless Steel Bipolar Plates. MATERIALS 2019; 12:ma12060899. [PMID: 30889839 PMCID: PMC6470975 DOI: 10.3390/ma12060899] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 03/09/2019] [Accepted: 03/14/2019] [Indexed: 12/21/2022]
Abstract
Research on the conductivity and corrosion resistance of stainless steel bipolar plates in a proton exchange membrane fuel cell (PEMFC) is commonly performed in a normal-temperature environment (about 20 °C). However, these fuel cells must function in low-temperature environments (lower than 0 °C) in some conditions, such as in vehicle fuel cells and in portable power supplies that operate during the winter in northern China. Stainless steel bipolar plates have higher requirements in terms of their hydrophobic and anti-icing properties, in addition to needing high conductivity and corrosion resistance. In this study, carbon nanotubes (CNTs) are grown on the surface of 304 stainless steel (304 SS) without a catalyst coating by plasma-enhanced chemical vapor deposition (PECVD), which is a simple and cheap method that allows stainless steel to be used as bipolar plates in low-temperature environments. The Raman spectroscopy and scanning electron microscopy (SEM) results show that the CNTs grown on the surface of 304 SS have different morphologies. The stainless steel samples with different CNT morphologies are tested by hydrophobicity and in situ icing experiments to prove that vertical CNTs can achieve a superhydrophobic state and have good anti-icing properties. The interfacial contact resistance (ICR) of the bare 304 SS and the 304 SS with vertical CNTs is compared by voltammetry, and then the corrosion resistances of both types is compared in a simulated PEMFC environment via a three-electrode system. Consequently, the ICR of the 304 SS with vertical CNTs was lower than the bare 304 SS. The corrosion potential was positive, and the corrosion current density was greatly reduced for the stainless steel with vertical CNTs grown directly on its surface when compared with the bare 304 SS. The experimental results show that vertical CNTs have good application prospects as bipolar plates for PEMFCs in low-temperature environments.
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Affiliation(s)
- Congda Lu
- Key Laboratory of E&M, Zhejiang University of Technology, Hangzhou 310014, China.
| | - Fengye Shi
- Key Laboratory of E&M, Zhejiang University of Technology, Hangzhou 310014, China.
| | - Jing Jin
- Key Laboratory of E&M, Zhejiang University of Technology, Hangzhou 310014, China.
| | - Xiang Peng
- Key Laboratory of E&M, Zhejiang University of Technology, Hangzhou 310014, China.
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21
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Liu C, Sun J, Zhuang Y, Wei J, Li J, Dong L, Yan D, Hu A, Zhou X, Wang Z. Self-propelled droplet-based electricity generation. NANOSCALE 2018; 10:23164-23169. [PMID: 30515499 DOI: 10.1039/c8nr08772e] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Droplets are ubiquitous in nature and the preferential control of droplet transport offers limitless potential for efficient mass and momentum transfer as well as energy conversion. In this work, we show that even without the need for any external energy input, the self-propelled motion of droplets driven by a surface wetting gradient can lead to reliable electricity generation. Simple analytical analysis demonstrates that the output voltage results from the modulation of the surface charge distribution on the dynamically changing solid/liquid interfaces, which can be programmed by tailoring the wetting gradient and the size of the droplet. We demonstrate that a self-propelled 25 μL droplet can generate a peak current of 93.5 nA and a maximum output power of 2.4 nW. This work provides a new angle for optimizing energy harvesting devices based on liquid-solid interfaces.
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Affiliation(s)
- Chaoran Liu
- College of Electronics and Information, Hangzhou Dianzi University, Hangzhou 310018, China and Science and Technology on Microsystem Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
| | - Jing Sun
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
| | - Yu Zhuang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
| | - Jie Wei
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
| | - Jing Li
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
| | - Linxi Dong
- College of Electronics and Information, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Dongfang Yan
- College of Computer Science and Engineering, Chongqing Three Gorges University, 780 Shalong Road, Chongqing 404100, China
| | - Alice Hu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
| | - Xiaofeng Zhou
- Science and Technology on Microsystem Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
| | - Zuankai Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
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22
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Dhiman S, Jayaprakash KS, Iqbal R, Sen AK. Self-Transport and Manipulation of Aqueous Droplets on Oil-Submerged Diverging Groove. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:12359-12368. [PMID: 30226788 DOI: 10.1021/acs.langmuir.8b01889] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report experimental study of self-transport of aqueous droplets along an oil-submerged diverging groove structure. The migration phenomenon is illustrated, and the effect of various parameters such as droplet size d, oil layer thickness h, groove angle 2θ, and groove thickness δ on the droplet transport behavior (i.e., migration velocity and length) is investigated. Our study reveals that complete engulfment of aqueous droplets in the oil layer, that is attributed to a positive spreading parameter ( S > 0), is a prerequisite for the droplet transport. The results show that only droplets of diameter larger than the oil layer thickness (i.e., d ≥ h) get transported owing to a differential Laplace pressure between the leading and trailing faces of a droplet because of the diverging groove. Using experimental data, the variation of droplet migration velocity with distance along the diverging groove is correlated as U( x) = ψ x-0.9, where ψ = d0.32θ-2.2 h-1.5δ0.7. The submerged groove structure was used to demonstrate simultaneous and sequential coalescence and transport of multiple droplets. Finally, the submerged groove structure was employed for extraction of aqueous droplets from oil. The proposed technique opens up a new avenue for evaporation and contamination free transport and coalescence of droplets for chemical and biological applications.
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Affiliation(s)
- S Dhiman
- Department of Mechanical Engineering , Indian Institute of Technology Madras , Chennai 600036 , India
| | - K S Jayaprakash
- Department of Mechanical Engineering , Indian Institute of Technology Madras , Chennai 600036 , India
| | - R Iqbal
- Department of Mechanical Engineering , Indian Institute of Technology Madras , Chennai 600036 , India
| | - A K Sen
- Department of Mechanical Engineering , Indian Institute of Technology Madras , Chennai 600036 , India
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23
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Scalable superhydrophobic coating with controllable wettability and investigations of its drag reduction. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.07.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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24
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Li J, Guo Z. Spontaneous directional transportations of water droplets on surfaces driven by gradient structures. NANOSCALE 2018; 10:13814-13831. [PMID: 30010683 DOI: 10.1039/c8nr04354j] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Spontaneous directional transportation of droplets on solid surfaces driven by structure gradients has attracted much attention due to its large-scale applications, such as heat transfer, microfluidic devices, water collection, and separation. It also provides new insight for theoretical research into the interactions between droplets and solid surfaces. This review article summarizes recent progress in the spontaneous directional transportation of droplets on surfaces with structure gradients. Currently, surfaces with structure gradients can be divided into three types: wedge corners with a gradient opening angle, wedge-shaped surfaces, and conical substrates. This review focuses on their basic theory, detailed transport processes, fabrication methods, influence factors and application development. Finally, a perspective of this mode of transportation for future development is proposed.
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Affiliation(s)
- Jian Li
- Hubei Collaborative Innovation Centre for Advanced Organic Chemical Materials and Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062, People's Republic of China and State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China.
| | - Zhiguang Guo
- Hubei Collaborative Innovation Centre for Advanced Organic Chemical Materials and Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062, People's Republic of China and State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China.
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25
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Si Y, Yu C, Dong Z, Jiang L. Wetting and spreading: Fundamental theories to cutting-edge applications. Curr Opin Colloid Interface Sci 2018. [DOI: 10.1016/j.cocis.2017.12.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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26
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Wang X, Liu A, Xing Y, Duan H, Xu W, Zhou Q, Wu H, Chen C, Chen B. Three-dimensional graphene biointerface with extremely high sensitivity to single cancer cell monitoring. Biosens Bioelectron 2018; 105:22-28. [DOI: 10.1016/j.bios.2018.01.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/02/2018] [Accepted: 01/08/2018] [Indexed: 10/18/2022]
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27
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Patternable Poly(chloro-p-xylylene) Film with Tunable Surface Wettability Prepared by Temperature and Humidity Treatment on a Polydimethylsiloxane/Silica Coating. MATERIALS 2018; 11:ma11040486. [PMID: 29570696 PMCID: PMC5951332 DOI: 10.3390/ma11040486] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 03/13/2018] [Accepted: 03/19/2018] [Indexed: 11/29/2022]
Abstract
Poly(chloro-p-xylylene) (PPXC) film has a water contact angle (WCA) of only about 84°. It is necessary to improve its hydrophobicity to prevent liquid water droplets from corroding or electrically shorting metallic circuits of semiconductor devices, sensors, microelectronics, and so on. Herein, we reported a facile approach to improve its surface hydrophobicity by varying surface pattern structures under different temperature and relative humidity (RH) conditions on a thermal curable polydimethylsiloxane (PDMS) and hydrophobic silica (SiO2) nanoparticle coating. Three distinct large-scale surface patterns were obtained mainly depending on the contents of SiO2 nanoparticles. The regularity of patterns was mainly controlled by the temperature and RH conditions. By changing the pattern structures, the surface wettability of PPXC film could be improved and its WCA was increased from 84° to 168°, displaying a superhydrophobic state. Meanwhile, it could be observed that water droplets on PPXC film with superhydrophobicity were transited from a “Wenzel” state to a “Cassie” state. The PPXC film with different surface patterns of 200 μm × 200 μm and the improved surface hydrophobicity showed wide application potentials in self-cleaning, electronic engineering, micro-contact printing, cell biology, and tissue engineering.
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28
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Guo L, Tang GH. Dropwise condensation on bioinspired hydrophilic-slippery surface. RSC Adv 2018; 8:39341-39351. [PMID: 35558060 PMCID: PMC9090926 DOI: 10.1039/c8ra08190e] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 11/12/2018] [Indexed: 11/29/2022] Open
Abstract
To promote the water vapor condensation efficiency in the presence of a non-condensable gas, both high nucleation rate and efficient droplet departure are desired on the condensing surface. Superhydrophobic surfaces with large water contact angles ensure the dropwise condensation mode and efficient droplet departure ability. Alternatively, efficient nucleation requires the surface to be hydrophilic. To combine these two seemingly contradictory factors on a single surface, we presented a copper-based hydrophilic-slippery surface in this study by depositing a lubricant (trimethoxysilane) on the microstructured copper substrate. The water droplet had both low contact angles and sliding angles on the surface, and stable dropwise condensation could be realized with and without non-condensable gas. The present hydrophilic-slippery surface demonstrated promising potential to enhance condensation heat transfer, particularly for cases with non-condensable gas. Improved droplet mobility was observed as compared to a superhydrophobic surface, hydrophobic surface, and hydrophobic-slippery surface. The most attractive feature lies in the enhanced nucleation process due to hydrophilicity, which is more favorable as it requires small subcooling degree and large non-condensable gas content. By revealing that a sliding angle could be accompanied by a small contact angle, this hydrophilic-slippery surface could improve our understanding in designing new functional surfaces for phase change, anti-icing, self-cleaning, and anti-fouling applications. A hydrophilic-slippery copper surface is fabricated, reconciling two required factors, enhanced condensation and efficient water transport. Nucleation rate, droplet mobility and heat transfer are enhanced by the small contact angle and sliding angle.![]()
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Affiliation(s)
- L. Guo
- MOE Key Laboratory of Thermo-Fluid Science and Engineering
- School of Energy and Power Engineering
- Xi'an Jiaotong University
- Xi'an 710049
- P. R. China
| | - G. H. Tang
- MOE Key Laboratory of Thermo-Fluid Science and Engineering
- School of Energy and Power Engineering
- Xi'an Jiaotong University
- Xi'an 710049
- P. R. China
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29
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Ding H, Lv J, Wu H, Chai G, Liu A. Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance. ROYAL SOCIETY OPEN SCIENCE 2018; 5:171350. [PMID: 29410838 PMCID: PMC5792915 DOI: 10.1098/rsos.171350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 12/14/2017] [Indexed: 06/08/2023]
Abstract
A 'sandwich'-structured TiO2NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy 'antennas' to trap the local-field light near the TiO2NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO2NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO2NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices.
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Affiliation(s)
- Hao Ding
- Key Laboratory of E&M, Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
| | - Jindian Lv
- Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China
| | - Huaping Wu
- Key Laboratory of E&M, Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
| | - Guozhong Chai
- Key Laboratory of E&M, Ministry of Education, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China
| | - Aiping Liu
- Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018, People's Republic of China
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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30
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Zhang P, Zhang L, Chen H, Dong Z, Zhang D. Surfaces Inspired by the Nepenthes Peristome for Unidirectional Liquid Transport. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 28782892 DOI: 10.1002/adma.201702995] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 06/23/2017] [Indexed: 05/15/2023]
Abstract
The slippery peristome of the pitcher plant Nepenthes has attracted much attention due to its unique function for preying on insects. Recent findings on the peristome surface of Nepenthes alata demonstrate a fast and continuous unidirectional liquid transport, which is enabled by the combination of a pinning effect at the sharp edges and a capillary rise in the wedge, deriving from the multiscale structure, which provides inspiration for designing and fabricating functional surfaces for unidirectional liquid transport. Developments in the fabrication methods of peristome-inspired surfaces and control methods for liquid transport are summarized. Both potential applications in the fields of microfluidic devices, biomedicine, and mechanical engineering and directions for further research in the future are discussed.
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Affiliation(s)
- Pengfei Zhang
- School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, China
| | - Liwen Zhang
- School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, China
| | - Huawei Chen
- School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, China
| | - Zhichao Dong
- CAS Key Laboratory of Bio-inspired Materials and Interfacial Science, CAS Center for Excellence in Nanoscience, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Deyuan Zhang
- School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, China
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31
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Banuprasad TN, Vinay TV, Subash CK, Varghese S, George SD, Varanakkottu SN. Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient. ACS APPLIED MATERIALS & INTERFACES 2017; 9:28046-28054. [PMID: 28750164 DOI: 10.1021/acsami.7b07451] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. Herein, for the first time, we report on-demand, fast, and reconfigurable droplet manipulation over a PNIPAAm grafted structured polymer surface using temperature-induced wettability gradient. Our study reveals that the PNIPAAm grafted on intrinsically superhydrophobic surfaces exhibit hydrophilic nature with high contact angle hysteresis below 30 °C and superhydrophobic nature with ultralow contact angle hysteresis above 36 °C. The transition region between 30 and 36 °C is characterized by a large change in water contact angle (∼100°) with a concomitant change in contact angle hysteresis. By utilizing this "transport zone" wherein driving forces overcome the frictional forces, we demonstrate macroscopic transport of water drops with a maximum transport velocity of approximately 40 cm/s. The theoretical calculations on the force measurements concur with dominating behavior of driving forces across the transport zone. The tunability in transport velocity by varying the temperature gradient along the surface or the inclination angle of the surface (maximum angle of 15° with a reduced velocity 0.4 mm/s) is also elucidated. In addition, as a practical application, coalescence of water droplets is demonstrated by using the temperature controlled wettability gradient. The presented results are expected to provide new insights on the design and fabrication of smart multifunctional surfaces for applications such as biochemical analysis, self-cleaning, and microfluidics.
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Affiliation(s)
| | | | | | - Soney Varghese
- School of Nano Science and Technology, National Institute of Technology , Calicut 673 601, India
| | - Sajan D George
- Centre for Applied Nanosciences, Department of Atomic and Molecular Physics, Manipal University , Karnataka 576 104, India
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32
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Gao Q, He L, Li Y, Ran X, Guo L. Controllable wettability and adhesion of superhydrophobic self-assembled surfaces based on a novel azobenzene derivative. RSC Adv 2017. [DOI: 10.1039/c7ra08465j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Solvent regulated wettability and adhesion transformations on superhydrophobic surfaces have been achieved based on a novel azobenzene derivative, AOB-Y8.
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Affiliation(s)
- Qiongqiong Gao
- Institute of Micro/Nano Photonic Materials and Application
- Henan University
- Kaifeng 475004
- China
| | - Liu He
- Institute of Micro/Nano Photonic Materials and Application
- Henan University
- Kaifeng 475004
- China
| | - Yajie Li
- Institute of Micro/Nano Photonic Materials and Application
- Henan University
- Kaifeng 475004
- China
| | - Xia Ran
- Institute of Micro/Nano Photonic Materials and Application
- Henan University
- Kaifeng 475004
- China
| | - Lijun Guo
- Institute of Micro/Nano Photonic Materials and Application
- Henan University
- Kaifeng 475004
- China
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