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Liu G, Yang J, Zhang K, Wu H, Yan H, Yan Y, Zheng Y, Zhang Q, Chen D, Zhang L, Zhao Z, Zhang P, Yang G, Chen H. Recent progress on the development of bioinspired surfaces with high aspect ratio microarray structures: From fabrication to applications. J Control Release 2024; 367:441-469. [PMID: 38295991 DOI: 10.1016/j.jconrel.2024.01.054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/12/2024] [Accepted: 01/25/2024] [Indexed: 02/05/2024]
Abstract
Surfaces with high aspect ratio microarray structures can implement sophisticated assignment in typical fields including microfluidics, sensor, biomedicine, et al. via regulating their deformation or the material properties. Inspired by natural materials and systems, for example sea cockroaches, water spiders, cacti, lotus leaves, rice leaves, and cedar leaves, many researchers have focused on microneedle functional surface studies. When the surface with high aspect ratio microarray structures is stimulated by the external fields, such as optical, electric, thermal, magnetic, the high aspect ratio microarray structures can undergo hydrophilic and hydrophobic switching or shape change, which may be gifted the surfaces with the ability to perform complex task, including directional liquid/air transport, targeted drug delivery, microfluidic chip sensing. In this review, the fabrication principles of various surfaces with high aspect ratio microarray structures are classified and summarized. Mechanisms of liquid manipulation on hydrophilic/hydrophobic surfaces with high aspect ratio microarray structures are clarified based on Wenzel model, Cassie model, Laplace pressure theories and so on. Then the intelligent control strategies have been demonstrated. The applications in microfluidic, drug delivery, patch sensors have been discussed. Finally, current challenges and new insights of future prospects for dynamic manipulation of liquid/air based on biomimetic surface with high aspect ratio microarray structures are also addressed.
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Affiliation(s)
- Guang Liu
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China
| | - Jiajun Yang
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China
| | - Kaiteng Zhang
- School of Mechanical Engineering and Automation, Beihang University, Beijing, China
| | - Hongting Wu
- Zhongtong Bus Holding Co., Ltd, Liaocheng, Shandong, China
| | - Haipeng Yan
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China
| | - Yu Yan
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China
| | - Yingdong Zheng
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China
| | - Qingxu Zhang
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China
| | - Dengke Chen
- College of Transportation, Ludong University, Yantai, Shandong, China
| | - Liwen Zhang
- School of Mechanical Engineering and Automation, Beihang University, Beijing, China
| | - Zehui Zhao
- School of Mechanical Engineering and Automation, Beihang University, Beijing, China
| | - Pengfei Zhang
- School of Mechanical Engineering and Automation, Beihang University, Beijing, China
| | - Guang Yang
- School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei, China.
| | - Huawei Chen
- School of Mechanical Engineering and Automation, Beihang University, Beijing, China.
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2
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Yu Y, Zhang D, Nagayama G. Estimation of surface free energy at microstructured surface to investigate intermediate wetting state for partial wetting model. SOFT MATTER 2023; 19:1249-1257. [PMID: 36722932 DOI: 10.1039/d2sm01406h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
While partial wetting at nano-/microstructured surfaces can be described using the intermediate wetting state between the Cassie-Baxter and Wenzel states, the limitations of the partial wetting model remain unclear. In this study, we performed surface free energy analysis at a microstructured Si-water interface from both theoretical and experimental viewpoints. We experimentally measured the water contact angle on microstructured Si surfaces with square holes and compared the measured values with theoretical predictions. Furthermore, the surface free energy was analyzed using the effective wetting area estimated from the measured contact angle and electrochemical impedance spectroscopy results. We verified the validity of the partial wetting model for fabricated Si surfaces with a hole aperture a less than 230 μm and a hole height h of 12 μm, and for a < 400 μm, h = 40 μm. The model was found to be applicable to microstructured Si surfaces with a/h < 10.
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Affiliation(s)
- Yankun Yu
- Graduate School of Engineering, Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan
| | - Dejian Zhang
- School of Mechanical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Daxue Road 3501, Changqing, Jinan, Shandong 250316, China
| | - Gyoko Nagayama
- Department of Mechanical Engineering, Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan.
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Guo L, Sheng Q, Kumar S, Liu Z, Tang G. Lubricant-induced tunability of self-driving nanodroplets on conical grooves. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.121149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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4
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Chen S, Dai Q, Yang X, Liu J, Huang W, Wang X. Bioinspired Functional Structures for Lubricant Control at Surfaces and Interfaces: Wedged-Groove with Oriented Capillary Patterns. ACS APPLIED MATERIALS & INTERFACES 2022; 14:42635-42644. [PMID: 36083010 DOI: 10.1021/acsami.2c09439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In this work, a design concept of bioinspired functional surfaces is proposed for lubricant control at surfaces and interfaces subjected to external thermal gradients. Inspired by the conical structures of cactus and the motion configuration of Centipedes, a bioinspired surface of wedged-groove with an oriented capillary pattern is constructed. The effect of geometrical parameters on the directional lubricant manipulation capacity and sliding anisotropy is discussed. It is found that by regulating the orientation of the capillary pattern, a controllable lubricant self-transport capacity can be achieved for varying conditions from surfaces to interfaces, with or without thermal gradients. The lubricant self-transport process is captured, and the mechanism is revealed. The design philosophy of the proposed bioinspired functional surface is believed to have potential applications for lubricant control in modern machinery and complex liquid control in lab-on-a-chip and microfluidics devices.
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Affiliation(s)
- Sangqiu Chen
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Qingwen Dai
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
- Institute for Nano- and Microfluidics, Technische Universität Darmstadt, Darmstadt 64287, Germany
- State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, China
| | - Xiaolong Yang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
- Aero-Engine Thermal Environment and Structure Key Laboratory of Ministry of Industry and Information Technology, Nanjing 210016, China
| | - Jiongjie Liu
- Institute for Materialwissenschaft, Technische Universität Darmstadt, Darmstadt 64287, Germany
| | - Wei Huang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Xiaolei Wang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
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Ye H, Yin C, Wang J, Zheng Y. Controllable and Gradient Wettability of Bilayer Two-Dimensional Materials Regulated by Interlayer Distance. ACS APPLIED MATERIALS & INTERFACES 2022; 14:41489-41498. [PMID: 36001530 DOI: 10.1021/acsami.2c08282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Surfaces with controllable and gradient wettability often require an elaborate design of the microstructure or its response under electrical, thermal, optical, pH, and other stimuli. Generally, the wettability change under these physical or chemical effects relies on a complex mechanism that is difficult to be quantitatively described. In this study, an online controlling strategy for surface wettability and the corresponding theoretical model are put forward based on a bilayer graphene-like atomic structure. Molecular dynamics results indicate that the surface wettability varies toward hydrophilicity after sticking a bottom material regardless of its wettability. But such an influence becomes weak with increasing interlayer distance, and the overall wettability approaches that of the upper layer material gradually. This variation is elucidated by the increase of the work of adhesion, providing new insight into the wetting transparency of graphene. A theoretical model of the governing relationship is established based on the work of adhesion, which correlates the overall surface wettability with the interlayer distance and the wettabilities of individual materials. Moreover, a surface with a uniform wettability gradient is achieved by inclining the bottom material. The spontaneous and steady motion of droplets can be induced by this gradient wettability. The relevant speedup behavior is evaluated through a theoretical model considering the varying interlayer distance, which reveals the critical role of the lower layer. This study proposes a novel strategy for controllable wetting and relevant gradient surfaces using prevailing two-dimensional materials, paving new routes to many applications such as microfluidic chips, virus diagnosis, and intelligent sensors.
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Affiliation(s)
- Hongfei Ye
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
| | - Chenguang Yin
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
| | - Jian Wang
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. China
| | - Yonggang Zheng
- International Research Center for Computational Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024, P. R. 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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7
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Al Balushi KM, Sefiane K, Orejon D. Binary mixture droplet wetting on micro-structure decorated surfaces. J Colloid Interface Sci 2022; 612:792-805. [PMID: 35065463 DOI: 10.1016/j.jcis.2021.12.171] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 12/17/2021] [Accepted: 12/26/2021] [Indexed: 10/19/2022]
Abstract
Liquid surface tension as well as solid structure play a paramount role on the intimate wetting and non-wetting regimes and interactions between liquids droplets and solid substrates. We hypothesise that the coupling of these two variables, independently addressed in the past, eventually offer a wider range of understanding to the surface science and interfacial communities. In this work, intrinsically hydrophobic micro-pillared surfaces varying in the spacing between structures, and pure ethanol, pure water and their binary mixtures (as well as acetone-water and ethylene glycol-water mixtures) are utilised, accessing a wide range of substrate solid fractions and liquid surface tensions experimentally. Wettability measurements are carried out at different azimuthal directions to exemplify the wetting/non-wetting behaviour as well as the droplet asymmetry function of both liquid composition and structure spacing. Our findings reveal that high water concentration droplets, i.e., high surface tension fluids, sit in the Cassie-Baxter regime while partial non-wetting Wenzel or mixed-mode regimes with enhanced droplet asymmetry ensuing for medium and high ethanol concentrations, i.e., low surface tension fluids, below certain micropillar spacing. Beyond micropillar spacing s ≥ 40 µm, the impact of the surface structure on the droplet shape is negligible, and droplets adopt a similar contact angle and circular shape as on a flat smooth hydrophobic surface. Wetting and non-wetting regimes are then supported by classical wetting theories and equations. A wetting regime map for a wide range of surface tension fluids and/or their mixtures on a wide domain of solid fractions is then proposed.
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Affiliation(s)
- Khaloud Moosa Al Balushi
- Institute for Multiscale Thermofluids, School of Engineering, The University of Edinburgh, Edinburgh EH9 3FD, Scotland, UK; Department of Engineering, The University of Technology and Applied Sciences, Suhar 311, Oman
| | - Khellil Sefiane
- Institute for Multiscale Thermofluids, School of Engineering, The University of Edinburgh, Edinburgh EH9 3FD, Scotland, UK
| | - Daniel Orejon
- Institute for Multiscale Thermofluids, School of Engineering, The University of Edinburgh, Edinburgh EH9 3FD, Scotland, UK; International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
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8
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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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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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Tang Q, Liu X, Cui X, Su Z, Zheng H, Tang J, Joo SW. Contactless Discharge-Driven Droplet Motion on a Nonslippery Polymer Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:14697-14702. [PMID: 34894688 DOI: 10.1021/acs.langmuir.1c02462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Droplet manipulation is the cornerstone of many modern technologies. It is still challenging to drive the droplet motion on nonslippery surfaces flexibly. We present a droplet manipulation method on nonslippery polymer surfaces based on the corona discharge. With the corona discharge of two-needle electrodes with opposite polarities, the droplet's charge polarity can be switched, which results in the directionally droplet transport on a charged polymer surface with the oscillation. Here, such droplet behaviors are presented in detail. Dependence of the motion on the critical distance and driving distance between the droplet and the needle electrode is revealed. The driving mechanism is verified by experiments and simulations. This work enriches the droplet manipulation techniques on nonslippery surfaces for various applications, such as combinatory chemistry, biochemical, and medical detection.
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Affiliation(s)
- Qiang Tang
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Xiaofeng Liu
- School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China
| | - Xiaxia Cui
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Zhenpeng Su
- School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China
| | - Huai Zheng
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
- School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China
| | - Jau Tang
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Sang Woo Joo
- School of Mechanical Engineering, Yeungnam University, Gyeongsan 38541, South Korea
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Ni E, Lu K, Song L, Jiang Y, Li H. Regular Self-Actuation of Liquid Metal Nanodroplets in Radial Texture Gradient Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:13654-13663. [PMID: 34747618 DOI: 10.1021/acs.langmuir.1c02249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Liquid metal movement in microfluidic devices generally requires an external stimulus to achieve its motion, which results in many difficulties to precisely manipulate its motion at a nanoscale. Therefore, there is an attempt to control the motion of a liquid metal droplet without the input of an external force. In this paper, we report an approach to achieve the self-actuation of a gallium nanodroplet in radial texture gradients on substrates. The results have proved the validity of this method. It is suggested that there are four stages in the self-motion of the droplet and that the precursor film forming on the second stage plays a pivotal role in the motion. Furthermore, how the impact velocity affects the self-actuation of the nanodroplet on the gradient surface is also studied. We find that the moderate impacting velocity hinders the self-actuation of the gallium nanodroplet. This study is very helpful to regulate the self-actuation on patterned substrates and facilitate their applications in the fields of microfluidics devices, soft robots, and liquid sensors.
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Affiliation(s)
- Erli Ni
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
| | - Kaida Lu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
| | - Lin Song
- State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
| | - Yanyan Jiang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
- Shenzhen Research Institute of Shandong University, Shenzhen 518057, China
| | - Hui Li
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
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12
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Zhang D, Takase S, Nagayama G. Measurement of effective wetting area at hydrophobic solid-liquid interface. J Colloid Interface Sci 2021; 591:474-482. [PMID: 33640849 DOI: 10.1016/j.jcis.2021.01.056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 12/31/2020] [Accepted: 01/19/2021] [Indexed: 10/22/2022]
Abstract
HYPOTHESES The effective wetting area, a parameter somewhat different from the apparent contact area at solid-liquid interfaces, plays a significant role in surface wettability. However, determination of the effective wetting area for hydrophobic surfaces remains an open question. In the present study, we developed an electrochemical impedance method to evaluate the effective wetting area at a hydrophobic solid-liquid interface. EXPERIMENTS Patterned Si surfaces were prepared using the anisotropic wet etching method, and the water contact angle and electrochemical impedance were measured experimentally. The effective wetting area at the solid-liquid interface was examined based on the wettability and impedance results. FINDINGS The electrochemical impedance for the patterned Si surfaces increased with increasing surface hydrophobicity, whereas the effective wetting area decreased. The intermediate wetting state (i.e. partial wetting model) was confirmed at the patterned Si surfaces, and the effective wetting area was theoretically estimated. The effective wetting area predicted from the electrochemical impedance agreed well with that predicted from the partial wetting model, thereby demonstrating the validity of the electrochemical impedance method for evaluating the effective wetting area at the hydrophobic solid-liquid interface.
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Affiliation(s)
- Dejian Zhang
- Department of Mechanical Engineering, Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan
| | - Satoko Takase
- Department of Chemical Engineering, Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan
| | - Gyoko Nagayama
- Department of Mechanical Engineering, Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan.
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13
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Liu C, Sun K, Lu C, Su J, Han L, Wang Z, Liu Y. One-step process for dual-scale ratchets with enhanced mobility of Leidenfrost droplets. J Colloid Interface Sci 2020; 569:229-234. [PMID: 32113020 DOI: 10.1016/j.jcis.2020.02.076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 02/16/2020] [Accepted: 02/17/2020] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS Droplet depositing onto hot surfaces above the so-called Leidenfrost temperature will float on a cushion of its own vapor. The vapor flow below the drop could be rectified by asymmetric surface textures, resulting the self-propelled droplet motion. Asymmetric structures like ratchets are used to rectify Leidenfrost droplet movement. Hence, it is possible to enhance the droplet mobility using surfaces with combined asymmetric macro/micro-structures. EXPERIMENTS Continuous scale-like microcraters stacked end-to-end were fabricated on steel surfaces by wire electrical discharge machining (WEDM). The crater orientation always vectored towards the machining direction (MD), which oriented the droplet motion. Further, by integrating micro and macro-ratchets, dual-scale ratchets were constructed by one-step process using WEDM. The travelling velocities of Leidenfrost droplets on dual-scale and traditional single-scale ratchets were compared and the enhanced mechanism on dual-scale ratchets was analyzed. FINDINGS One-step process was developed to fabricate transport platforms for Leidenfrost droplets, that continuous scale-like microcraters formed simultaneously on the macroratchets. The highest droplet travelling velocity was achieved compared to previous research. Further study shows that the enhanced drop mobility is attributed to the dual-scale roughness which endows a larger propelling force. This finding presents a high-efficiency method to fabricate transport platforms for Leidenfrost droplets.
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Affiliation(s)
- Cong Liu
- Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Kuan Sun
- Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Chenguang Lu
- Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Junpeng Su
- Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Libao Han
- Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Zuankai Wang
- Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Yahua Liu
- Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China.
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14
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Kumar M, Bhardwaj R, Sahu KC. Wetting Dynamics of a Water Droplet on Micropillar Surfaces with Radially Varying Pitches. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:5312-5323. [PMID: 32356997 DOI: 10.1021/acs.langmuir.0c00697] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The wetting dynamics of a sessile droplet on square micropillar substrates with radially varying pitches, prepared on silicon wafers using a photolithography technique, is investigated experimentally. Two configurations are considered, namely, substrates with radially increasing pitch and radially decreasing pitch. The droplet initially placed at the center experiences a wettability gradient because of the variation in pitch of the micropillar substrate leading to complex wetting dynamics. We observed that the droplet remains in the Cassie-Baxter state in the case of a radially increasing pitch and exhibits a higher contact angle than that on a smooth surface during its spreading stage. In contrast, the droplet experiences the Wenzel condition in the case of a radially decreasing pitch and assumes a lower contact angle relative to that observed on a smooth surface. The wetted diameter of the droplet in the radially decreasing pitch configuration is found to be smaller than that observed in the radially increasing pitch configuration. Our study also reveals that increasing the size of the pillars increases the wetted diameter of the droplet in both configurations. Theoretical models developed using the Cassie-Baxter and Wenzel states for the radially increasing and radially decreasing pitches satisfactorily predict the experimental behaviors.
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Affiliation(s)
- Manish Kumar
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Kirti Chandra Sahu
- Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502 285, Telangana, India
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Nagayama G, Zhang D. Intermediate wetting state at nano/microstructured surfaces. SOFT MATTER 2020; 16:3514-3521. [PMID: 32215385 DOI: 10.1039/c9sm02513h] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A general partial wetting model to describe an intermediate wetting state is proposed in this study to explain the deviations between the experimental results and classical theoretical wetting models for hydrophobic surfaces. We derived a theoretical partial wetting model for the static intermediate wetting state based on the thermodynamic energy minimization method. The contact angle based on the partial wetting model is a function of structural parameters and effective wetting ratio f, which agrees with the classical Wenzel and Cassie-Baxter models at f = 1 and 0, respectively. Si samples including porous surfaces, patterned surfaces and hierarchical nano/microstructured surfaces were prepared experimentally, having the same chemical composition but different physical morphology. We found that the experimental water contact angles deviate significantly from the classical Wenzel and Cassie-Baxter models but show good agreement with the proposed partial wetting model.
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Affiliation(s)
- Gyoko Nagayama
- Department of Mechanical Engineering, Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan.
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Orejon D, Askounis A, Takata Y, Attinger D. Dropwise Condensation on Multiscale Bioinspired Metallic Surfaces with Nanofeatures. ACS APPLIED MATERIALS & INTERFACES 2019; 11:24735-24750. [PMID: 31180632 DOI: 10.1021/acsami.9b06001] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Nonwetting surfaces engineered from intrinsically hydrophilic metallic materials are promising for self-cleaning, anti-icing, or condensation heat transfer applications where the durability of commonly applied hydrophobic coatings is an issue. In this work, we fabricate and study the wetting behavior and the condensation performance on two metallic nonwetting surfaces with varying number and size of roughness tiers without the need for further hydrophobic coating procedure. On one hand, the surface resembling a rose petal exhibits a sticky nonwetting behavior as drops wet the microscopic roughness features with consequent enhanced drop adhesion, which leads to filmwise condensation. On the other hand, the surface resembling a lotus leaf provides super-repellent nonwetting behavior prompting the continuous nucleation, growth, and departure of spherical drops in a dropwise condensation fashion. On a lotus leaf surface, the third nanoscale roughness tier (created by chemical oxidation) combined with ambience exposure prompts the growth of drops in the Cassie state with the benefit of minimal condensate adhesion. The two different condensation behaviors reported are well supported by a drop surface energy analysis, which accounts for the different wetting performance and the surface structure underneath the condensing drops. Further, we coated the above-mentioned surfaces with polydimethylsiloxane, which resulted in filmwise condensation due to the smoothening of the different roughness tiers. Continuous dropwise condensation on a hierarchical bioinspired lotus leaf metallic surface without the need for a conformal hydrophobic coating is hence demonstrated, which offers a novel path for the design and manufacture of noncoated metallic super-repellent surfaces for condensation phase change applications, among others.
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Affiliation(s)
- Daniel Orejon
- Institute for Multiscale Thermofluids, School of Engineering , The University of Edinburgh , Edinburgh EH9 3FD , Scotland, U.K
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
| | - Alexandros Askounis
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
- Engineering, Faculty of Science , University of East Anglia , Norwich Research Park , Norwich NR5 7TJ , U.K
| | - Yasuyuki Takata
- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
- Department of Mechanical Engineering, Thermofluid Physics Laboratory , Kyushu University , 744 Motooka , Nishi-ku, Fukuoka 819-0395 , Japan
| | - Daniel Attinger
- Deparment of Mechanical Engineering , Iowa State University , Ames , Iowa 50011 , United States
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