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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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2
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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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3
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Sinha Mahapatra P, Ganguly R, Ghosh A, Chatterjee S, Lowrey S, Sommers AD, Megaridis CM. Patterning Wettability for Open-Surface Fluidic Manipulation: Fundamentals and Applications. Chem Rev 2022; 122:16752-16801. [PMID: 36195098 DOI: 10.1021/acs.chemrev.2c00045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Effective manipulation of liquids on open surfaces without external energy input is indispensable for the advancement of point-of-care diagnostic devices. Open-surface microfluidics has the potential to benefit health care, especially in the developing world. This review highlights the prospects for harnessing capillary forces on surface-microfluidic platforms, chiefly by inducing smooth gradients or sharp steps of wettability on substrates, to elicit passive liquid transport and higher-order fluidic manipulations without off-the-chip energy sources. A broad spectrum of the recent progress in the emerging field of passive surface microfluidics is highlighted, and its promise for developing facile, low-cost, easy-to-operate microfluidic devices is discussed in light of recent applications, not only in the domain of biomedical microfluidics but also in the general areas of energy and water conservation.
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Affiliation(s)
- Pallab Sinha Mahapatra
- Micro Nano Bio-Fluidics group, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai600036, India
| | - Ranjan Ganguly
- Department of Power Engineering, Jadavpur University, Kolkata700098, India
| | - Aritra Ghosh
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois60607, United States
| | - Souvick Chatterjee
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois60607, United States
| | - Sam Lowrey
- Department of Physics, University of Otago, Dunedin9016, New Zealand
| | - Andrew D Sommers
- Department of Mechanical and Manufacturing Engineering, Miami University, Oxford, Ohio45056, United States
| | - Constantine M Megaridis
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois60607, United States
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Wang X, Xu B, Chen Z, Del Col D, Li D, Zhang L, Mou X, Liu Q, Yang Y, Cao Q. Review of droplet dynamics and dropwise condensation enhancement: Theory, experiments and applications. Adv Colloid Interface Sci 2022; 305:102684. [PMID: 35525088 DOI: 10.1016/j.cis.2022.102684] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 03/21/2022] [Accepted: 04/23/2022] [Indexed: 02/06/2023]
Abstract
Droplet dynamics and condensation phenomena are widespread in nature and industrial applications, and the fundamentals of various technological applications. Currently, with the rapid development of interfacial materials, microfluidics, micro/nano fabrication technology, as well as the intersection of fluid mechanics, interfacial mechanics, heat and mass transfer, thermodynamics and reaction kinetics and other disciplines, the preparation and design of various novel functional surfaces have contributed to the local modulation of droplets (including nucleation, jumping and directional migration) and the improvement of condensation heat transfer, further deepening the understanding of relevant mechanisms. The wetting and dynamic characteristics of droplets involve complex solid-liquid interfacial interactions, so that the local modulation of microdroplets and the extension of enhanced condensation heat transfer by means of complex micro/nano structures and hydrophilic/hydrophobic properties is one of the current hot topics in heat and mass transfer research. This work presents a detailed review of several scientific issues related to the droplet dynamics and dropwise condensation heat transfer under the influence of multiple factors (including fluid property, surface structure, wettability, temperature external field, etc.). Firstly, the basic theory of droplet wetting on the solid wall is introduced, and the mechanism of solid-liquid interfacial interaction involving droplet jumping and directional migration on the functional surfaces under the various influencing factors is discussed. Optimizing the surface structure for the local modulation of droplets is of guidance for condensation heat transfer. Secondly, we summarize the existing theoretical models of dropwise condensation applicable to various functional surfaces and briefly outline the current numerical models for simulating dropwise condensation at different scales, as well as the fabricating techniques of coatings and functional surfaces for enhancing heat transfer. Finally, the relevant problems and challenges are summarized and future research is discussed.
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Affiliation(s)
- Xin Wang
- School of Energy and Environment, Southeast University, Nanjing, PR China
| | - Bo Xu
- School of Energy and Environment, Southeast University, Nanjing, PR China
| | - Zhenqian Chen
- School of Energy and Environment, Southeast University, Nanjing, PR China; Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, PR China; Jiangsu Provincial Key Laboratory of Solar Energy Science and Technology, School of Energy and Environment, Southeast University, Nanjing, PR China.
| | - Davide Del Col
- Department of Industrial Engineering, University of Padua, Italy
| | - Dong Li
- School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, PR China
| | - Leigang Zhang
- School of Energy and Mechanical Engineering, Nanjing Normal University, Nanjing, PR China
| | - Xinzhu Mou
- School of Energy and Environment, Southeast University, Nanjing, PR China
| | - Qiusheng Liu
- Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing, PR China
| | - Yang Yang
- Engineering and technology center for space applications, Chinese academy of sciences, Beijing, PR China
| | - Qian Cao
- Engineering and technology center for space applications, Chinese academy of sciences, Beijing, PR China
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Yamada Y, Isobe K, Horibe A. Droplet motion on a wrinkled PDMS surface with a gradient structural length scale shorter than the droplet diameter. RSC Adv 2022; 12:13917-13923. [PMID: 35548386 PMCID: PMC9087903 DOI: 10.1039/d1ra09244h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 04/29/2022] [Indexed: 11/21/2022] Open
Abstract
Droplet transportation using a wettability gradient surface has attracted much attention owing to applications such as in microfluidic devices. A surface with a spatial structural gradient was prepared through a simple and cost-effective process even though understanding of droplet behavior on the structure was still limited. Here, we report impinging droplet motion on a gradient wrinkled surface. Surfaces were prepared through hard film deposition on soft pre-strained polydimethylsiloxane (PDMS) with a mask installed with a slit to control the amount of deposition, which is related to the wavelength of the wrinkles. Droplets were impinged with varying position with respect to the structure, and the droplet motion was observed in the direction away from the region under the slit. We found an asymmetric contact angle and alternate motion on both sides of the three-phase contact line during the motion according to the gradient of the wrinkle wavelength. These results may help not only to understand the behavior of droplet impingement on a gradient structural surface but also to further develop applications using directional droplet transfer.
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Affiliation(s)
- Yutaka Yamada
- Graduate School of Natural Science and Technology, Okayama University Okayama 700-8530 Japan +81 86 251 8046
| | - Kazuma Isobe
- Graduate School of Natural Science and Technology, Okayama University Okayama 700-8530 Japan +81 86 251 8046
| | - Akihiko Horibe
- Graduate School of Natural Science and Technology, Okayama University Okayama 700-8530 Japan +81 86 251 8046
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Raj SS, Mathew RM, Nair Y, S. T. A, T. P. V. Fabrication and Applications of Wrinkled Soft Substrates: An Overview. ChemistrySelect 2022. [DOI: 10.1002/slct.202200714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Soorya S. Raj
- Department of Chemistry CHRIST (Deemed to be University) Hosur Road Bangalore 560029 India
| | - Romina Marie Mathew
- Department of Chemistry CHRIST (Deemed to be University) Hosur Road Bangalore 560029 India
| | - Yamuna Nair
- Department of Chemistry CHRIST (Deemed to be University) Hosur Road Bangalore 560029 India
| | - Aruna S. T.
- Surface Engineering Division CSIR – National Aerospace Laboratories HAL Airport Road Bangalore 560017 India
| | - Vinod T. P.
- Department of Chemistry CHRIST (Deemed to be University) Hosur Road Bangalore 560029 India
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7
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Lowrey S, Misiiuk K, Blaikie R, Sommers A. Survey of Micro/Nanofabricated Chemical, Topographical, and Compound Passive Wetting Gradient Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:605-619. [PMID: 34498455 DOI: 10.1021/acs.langmuir.1c00612] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Surface wetting gradients are desirable due to their ability to passively transport liquid droplets without the aid of gravity. Such surfaces can be prepared through topographical or chemical methods or a compound approach involving both methods. By altering the surface free energy across a surface, a droplet that contacts such a surface will experience an actuation force toward the hydrophilic region. Such transport properties make these surfaces attractive for a range of applications from thermal management to microfluidics to the investigation of biomolecular interactions. This paper reviews passive wetting gradients that have been demonstrated over the last three decades, focusing on the types of surfaces that have been developed to date along with the materials that have been used. The corresponding wetting ranges and physical lengths over which droplet mobility has been achieved on these various types of gradient surfaces are compared to guide future developments.
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Affiliation(s)
- Sam Lowrey
- Department of Physics, University of Otago, Dunedin 9016, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Wellington, Wellington 6012, New Zealand
| | - Kirill Misiiuk
- Department of Physics, University of Otago, Dunedin 9016, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Wellington, Wellington 6012, New Zealand
| | - Richard Blaikie
- Department of Physics, University of Otago, Dunedin 9016, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Wellington, Wellington 6012, New Zealand
| | - Andrew Sommers
- Department of Mechanical & Manufacturing Engineering, Miami University, Oxford, Ohio 45056, United States
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8
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Knapp A, Nebel LJ, Nitschke M, Sander O, Fery A. Controlling line defects in wrinkling: a pathway towards hierarchical wrinkling structures. SOFT MATTER 2021; 17:5384-5392. [PMID: 33969367 DOI: 10.1039/d0sm02231d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We demonstrate a novel approach for controlling the line defect formation in microscopic wrinkling structures by patterned plasma treatment of elastomeric surfaces. Wrinkles were formed on polydimethylsiloxane (PDMS) surfaces exposed to low-pressure plasma under uniaxial stretching and subsequent relaxation. The wrinkling wavelength λ can be regulated via the treatment time and choice of plasma process gases (H2, N2). Sequential masking allows for changing these parameters on micron-scale dimensions. Thus, abrupt changes of the wrinkling wavelength become feasible and result in line defects located at the boundary zone between areas of different wavelengths. Wavelengths, morphology, and mechanical properties of the respective areas are investigated by Atomic Force Microscopy and agree quantitatively with predictions of analytical models for wrinkle formation. Notably, the approach allows for the first time the realization of a dramatic wavelength change up to a factor of 7 to control the location of the branching zone. This allows structures with a fixed but also with a strictly alternating branching behavior. The morphology inside the branching zone is compared with finite element methods and shows semi-quantitative agreement. Thus our finding opens new perspectives for "programming" hierarchical wrinkling patterns with potential applications in optics, tribology, and biomimetic structuring of surfaces.
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Affiliation(s)
- André Knapp
- Institute of Physical Chemistry and Polymer Physics, Leibniz Institute of Polymer Research Dresden e. V., Hohe Str. 6, 01069 Dresden, Germany.
| | - Lisa Julia Nebel
- Institute for Numerical Mathematics, Technical University Dresden, Zellescher Weg 12-14, 01069 Dresden, Germany.
| | - Mirko Nitschke
- Max Bergmann Center of Biomaterials, Leibniz Institute of Polymer Research Dresden e. V., Hohe Str. 6, 01069 Dresden, Germany
| | - Oliver Sander
- Institute for Numerical Mathematics, Technical University Dresden, Zellescher Weg 12-14, 01069 Dresden, Germany.
| | - Andreas Fery
- Institute of Physical Chemistry and Polymer Physics, Leibniz Institute of Polymer Research Dresden e. V., Hohe Str. 6, 01069 Dresden, Germany. and Chair for Physical Chemistry of Polymeric Materials, Technical University Dresden, Mommsenstr. 4, 01062 Dresden, Germany
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9
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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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10
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Gulina LB, Gurenko VE, Tolstoy VP, Mikhailovskii VY, Koroleva AV. Interface-Assisted Synthesis of the Mn 3-xFe xO 4 Gradient Film with Multifunctional Properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:14983-14989. [PMID: 31702162 DOI: 10.1021/acs.langmuir.9b02338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Anisotropic gradient materials are considered as promising and novel in that they have numerous functional properties and are able to transform into hierarchical microstructures. We report a facile method of gradient inorganic thin film synthesis through diffusion-controlled deposition at the gas-solution interface. To investigate the reaction of interfacial phase boundary controllable hydrolysis by gaseous ammonium, an aqueous solution of FeCl3 and MnCl2 was chosen, as the precipitation pH values for the hydroxides of these metals differ gradually. As a result of synthesis using the gas-solution interface technique (GSIT), a thin film is formed on the surface of the solution that consists of Mn2+(Fe,Mn)23+O4 nanoparticles with hausmannite crystal structure. The ratio between iron and manganese in the film can be adjusted over a wide range by varying the synthetic procedure. Specific conditions are determined that allow the formation of a Mn-Fe mixed oxide film with a gradient of composition, morphology, and properties, as well as its further transformation into microscrolls with a diameter of 10-20 μm and a length of up to 300 μm, showing weak superparamagnetic properties. The technique reported provides a new interfacial route for the development of functional gradient materials with tubular morphology.
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Affiliation(s)
- Larisa B Gulina
- Saint Petersburg State University , 7/9 Universitetskaya Nab. , St. Petersburg 199034 , Russia
| | - Vladislav E Gurenko
- Saint Petersburg State University , 7/9 Universitetskaya Nab. , St. Petersburg 199034 , Russia
| | - Valeri P Tolstoy
- Saint Petersburg State University , 7/9 Universitetskaya Nab. , St. Petersburg 199034 , Russia
| | | | - Alexandra V Koroleva
- Saint Petersburg State University , 7/9 Universitetskaya Nab. , St. Petersburg 199034 , Russia
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11
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Yu S, Ma L, Sun Y, Lu C, Zhou H, Ni Y. Controlled Wrinkling Patterns in Periodic Thickness-Gradient Films on Polydimethylsiloxane Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:7146-7154. [PMID: 31063390 DOI: 10.1021/acs.langmuir.9b00705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Surface wrinkles in homogeneous and heterogeneous film-substrate systems have received intense attention in both science and engineering. Understanding the wrinkling phenomena of heterogeneous systems with continuously variable features is still a challenge. In this work, we propose an unconventional strategy to prepare periodic thickness-gradient metal films on polydimethylsiloxane (PDMS) substrates by masking of copper grids which are weaved by orthometric copper wires. It is found that a periodic thickness-gradient film spontaneously forms during the sputtering process because of the specific structures of the copper grids. Surface wrinkles are strongly modulated by the copper grid structures and are position-dependent within a period. A phase diagram has been established to correlate the wrinkle morphology with the mesh size and film thickness. The film surfaces at mesh centers are evolved from labyrinth wrinkling to herringbone wrinkling and then to stripe wrinkling and finally to wrinkling-free state when the mesh size decreases and/or the film thickness increases. The morphological characteristics, evolutional behaviors, and underlying mechanisms of such wrinkling are discussed in detail based on the stress theory and numerical simulation.
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Affiliation(s)
- Senjiang Yu
- Innovative Center for Advanced Materials (ICAM) , Hangzhou Dianzi University , 1158, Number 2 Street , Hangzhou 310018 , P. R. China
| | - Long Ma
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics , University of Science and Technology of China , 96, Jinzhai Road , Hefei , Anhui 230026 , P. R. China
| | - Yadong Sun
- Department of Physics , China Jiliang University , 258, Xueyuan Street , Hangzhou 310018 , P. R. China
| | - Chenxi Lu
- Innovative Center for Advanced Materials (ICAM) , Hangzhou Dianzi University , 1158, Number 2 Street , Hangzhou 310018 , P. R. China
| | - Hong Zhou
- Department of Physics , China Jiliang University , 258, Xueyuan Street , Hangzhou 310018 , P. R. China
| | - Yong Ni
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics , University of Science and Technology of China , 96, Jinzhai Road , Hefei , Anhui 230026 , P. R. China
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12
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Schedl AE, Neuber C, Fery A, Schmidt HW. Controlled Wrinkling of Gradient Metal Films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:14249-14253. [PMID: 30388014 DOI: 10.1021/acs.langmuir.8b03123] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Controlled wrinkling is a rather simple method of fabricating surface topographies. The production process is based on the spontaneous formation of wrinkles upon compression of a hard film attached to a soft elastic substrate. Controlled wrinkling typically features large-scale wrinkled samples with a discrete wavelength and amplitude. In this report, we employ an approach utilizing linear metal layer thickness gradients for the controlled formation of gradient wrinkle patterns. The observed wavelength modulation was experimentally achieved by preparing layer thickness gradients of gold, chromium, and indium by physical vapor deposition in combination with a poly(dimethyl siloxane) elastomer substrate. In case of chromium and indium, a thin SiO x surface layer was sufficient to ensure adhesion. However, in case of gold, an additional thin chromium adhesion layer was required. For the wrinkled gradient gold film, it was possible to tune the wavelength from 3.4 to 12.2 μm on a single substrate. The experimental data correspond well to the theoretical bilayer model from Stafford et al. Chromium has a significant higher Young's modulus and melting temperature than gold. However, chromium was successfully evaporated and gradient wrinkle patterns with wavelengths from 1.0 to 3.5 μm were realized. In contrast, indium has a considerable lower Young's modulus than gold and chromium, respectively. Consequently, lower wavelengths (0.6-1.0 μm) of the wrinkled gradient indium film were observed. These tunable wrinkled gradient metal films can be envisioned as components in sensors and optical and electro-optical devices.
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Affiliation(s)
- Andreas E Schedl
- Macromolecular Chemistry I, Bavarian Polymer Institute (BPI) and Bayreuth Center for Colloids and Interfaces (BZKG) , University of Bayreuth , 95440 Bayreuth , Germany
| | - Christian Neuber
- Macromolecular Chemistry I, Bavarian Polymer Institute (BPI) and Bayreuth Center for Colloids and Interfaces (BZKG) , University of Bayreuth , 95440 Bayreuth , Germany
| | - Andreas Fery
- Institute of Physical Chemistry and Polymer Physics, Leibniz Institute of Polymer Research Dresden e. V. and Chair for Physical Chemistry of Polymeric Materials , Technical University Dresden , 01069 Dresden , Germany
| | - Hans-Werner Schmidt
- Macromolecular Chemistry I, Bavarian Polymer Institute (BPI) and Bayreuth Center for Colloids and Interfaces (BZKG) , University of Bayreuth , 95440 Bayreuth , Germany
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Parihar V, Bandyopadhyay S, Das S, Mukherjee R, Chakraborty S, Dasgupta S. Tailored topography: a novel fabrication technique using an elasticity gradient. SOFT MATTER 2018; 14:7034-7044. [PMID: 30109884 DOI: 10.1039/c8sm01054d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A facile methodology to create a wrinkled surface with a tailored topography is presented herein. The dependency of the elasticity of poly(dimethyl)siloxane (PDMS) on the curing temperature has been exploited to obtain a substrate with an elasticity gradient. The temperature gradient across the length of PDMS is created by a novel set-up consisting of a metal and insulator connected to a heater and the highest usable (no degradation of PDMS) temperature gradient is used. The time-dependent temperature distributions along the substrate are measured and the underlying physics of the dependence of the PDMS elasticity on the curing temperature is addressed. The PDMS substrate with the elasticity gradient is first stretched and subsequently oxidized by oxygen plasma. Upon relaxation, an ordered wrinkled surface with continuously varying wavelength and amplitude along the length of PDMS is obtained. The extent of hydrophobicity recovery of this plasma oxidized PDMS with varying elasticity has been studied. The change in the wavelength and amplitude of the regular patterns on the substrate can be controlled by varying operational parameters like applied pre-strain, plasma power and the heater temperature. It has been found that the spatial distributions of the topography and the hydrophobicity collectively decide the resultant wettability of the substrate. Such surfaces with gradients in the substructure dimensions demonstrate different wetting characteristics that may lead to a wide gamut of applications including droplet movement, cell adhesion and proliferation, diffraction grating etc.
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Affiliation(s)
- Vartika Parihar
- Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India.
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Park S, Nallainathan U, Mondal K, Sen P, Dickey MD. Light-Induced Buckles Localized by Polymeric Inks Printed on Bilayer Films. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1704460. [PMID: 29659190 DOI: 10.1002/smll.201704460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 02/13/2018] [Indexed: 06/08/2023]
Abstract
Buckling instabilities generate microscale features in thin films in a facile manner. Buckles can form, for example, by heating a metal/polymer film stack on a rigid substrate. Thermal expansion differences of the individual layers generate compressive stress that causes the metal to buckle over the entire surface. The ability to dictate and confine the location of buckle formation can enable patterns with more than one length scale, including hierarchical patterns. Here, sacrificial "ink" patterned on top of the film stack localizes the buckles via two mechanisms. First, stiff inks suppress buckles such that only the non-inked regions buckle in response to infrared light. The metal in the non-inked regions absorbs the infrared light and thus gets sufficiently hot to induce buckles. Second, soft inks that absorb light get hot faster than the non-inked regions and promote buckling when exposed to visible light. The exposed metal in the non-inked regions reflects the light and thus never get sufficiently hot to induce buckles. This second method works on glass substrates, but not silicon substrates, due to the superior thermal insulation of glass. The patterned ink can be removed, leaving behind hierarchical patterns consisting of regions of buckles among non-buckled regions.
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Affiliation(s)
- Sungjune Park
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 partners Way, Raleigh, NC, 27695, USA
| | - Umaash Nallainathan
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 partners Way, Raleigh, NC, 27695, USA
| | - Kunal Mondal
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 partners Way, Raleigh, NC, 27695, USA
| | - Pratik Sen
- Department of Mechanical and Aerospace Engineering, North Carolina State University, 911 Oval Drive, Raleigh, NC, 27695, USA
| | - Michael D Dickey
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 partners Way, Raleigh, NC, 27695, USA
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15
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Parihar V, Bandyopadhyay S, Das S, Dasgupta S. Anisotropic Electrowetting on Wrinkled Surfaces: Enhanced Wetting and Dependency on Initial Wetting State. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:1844-1854. [PMID: 29309153 DOI: 10.1021/acs.langmuir.7b03467] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electrowetting on dielectric (EWOD) on unidirectional microstructured surfaces has recently evoked significant interest as they can modulate the effect of electrowetting, and can thus find applications in directional wetting in microfluidic systems. However, the dependency of such EW phenomenon on their initial state of wetting and anisotropy is far from being well understood. The current study addresses the initial wetting states and their implication on the anisotropic electrowetting using a wrinkled EWOD platform. Herein we demonstrate a facile stampless and maskless structure generation technique to fabricate wrinkles of varying topography. Further, we have demonstrated alteration in the interfacial wetting conditions by modulating the wrinkle topography, and its effect on the droplet behavior during electrowetting. The capillary wicking-assisted electrowetting on these wrinkled surfaces is in specific direction dictated by the ordered wrinkles and prompts enhanced spreading of the droplet. We also demonstrate that while the enhancement of unidirectional electrowetting is stronger in conformal wetting state surfaces, composite wetting state surfaces depict a reversal in anisotropy.
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Affiliation(s)
- Vartika Parihar
- Department of Chemical Engineering, ‡Advanced Technology Development Centre, and §School of Medical Science and Technology, Indian Institute of Technology Kharagpur , Kharagpur-721302, West Bengal, India
| | - Saumyadwip Bandyopadhyay
- Department of Chemical Engineering, ‡Advanced Technology Development Centre, and §School of Medical Science and Technology, Indian Institute of Technology Kharagpur , Kharagpur-721302, West Bengal, India
| | - Soumen Das
- Department of Chemical Engineering, ‡Advanced Technology Development Centre, and §School of Medical Science and Technology, Indian Institute of Technology Kharagpur , Kharagpur-721302, West Bengal, India
| | - Sunando Dasgupta
- Department of Chemical Engineering, ‡Advanced Technology Development Centre, and §School of Medical Science and Technology, Indian Institute of Technology Kharagpur , Kharagpur-721302, West Bengal, India
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Zheng Y, Cheng J, Zhou C, Xing H, Wen X, Pi P, Xu S. Droplet Motion on a Shape Gradient Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4172-4177. [PMID: 28398753 DOI: 10.1021/acs.langmuir.7b00227] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We demonstrate a facile method to induce water droplet motion on an wedge-shaped superhydrophobic copper surface combining with a poly(dimethylsiloxane) (PDMS) oil layer on it. The unbalanced interfacial tension from the shape gradient offers the actuating force. The superhydrophobicity critically eliminates the droplet contact line pinning and the slippery PDMS oil layer lubricates the droplet motion, which makes the droplet move easily. The maximum velocity and furthest position of droplet motion were recorded and found to be influenced by the gradient angle. The mechanism of droplet motion on the shape gradient surface is systematically discussed, and the theoretical model analysis is well matched with the experimental results.
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Affiliation(s)
- Yanfen Zheng
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
| | - Jiang Cheng
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
| | - Cailong Zhou
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
| | - Haiting Xing
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
| | - Xiufang Wen
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
| | - Pihui Pi
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
| | - Shouping Xu
- School of Chemistry and Chemical Engineering, South China University of Technology , Guangzhou 510640, People's Republic of China
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