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Chu F, Hu Z, Feng Y, Lai NC, Wu X, Wang R. Advanced Anti-Icing Strategies and Technologies by Macrostructured Photothermal Storage Superhydrophobic Surfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2402897. [PMID: 38801015 DOI: 10.1002/adma.202402897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 04/23/2024] [Indexed: 05/29/2024]
Abstract
Water is the source of life and civilization, but water icing causes catastrophic damage to human life and diverse industrial processes. Currently, superhydrophobic surfaces (inspired by the lotus effect) aided anti-icing attracts intensive attention due to their energy-free property. Here, recent advances in anti-icing by design and functionalization of superhydrophobic surfaces are reviewed. The mechanisms and advantages of conventional, macrostructured, and photothermal superhydrophobic surfaces are introduced in turn. Conventional superhydrophobic surfaces, as well as macrostructured ones, easily lose the icephobic property under extreme conditions, while photothermal superhydrophobic surfaces strongly rely on solar illumination. To address the above issues, a potentially smart strategy is found by developing macrostructured photothermal storage superhydrophobic (MPSS) surfaces, which integrate the functions of macrostructured superhydrophobic materials, photothermal materials, and phase change materials (PCMs), and are expected to achieve all-day anti-icing in various fields. Finally, the latest achievements in developing MPSS surfaces, showcasing their immense potential, are highlighted. Besides, the perspectives on the future development of MPSS surfaces are provided and the problems that need to be solved in their practical applications are proposed.
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Affiliation(s)
- Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Zhifeng Hu
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
- Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China
| | - Yanhui Feng
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Nien-Chu Lai
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Xiaomin Wu
- Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China
| | - Ruzhu Wang
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
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2
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Li T, Liang S, Li Z, Bi J, Li H. Impact of Droplets on Surfaces Designed with Wettability-Gradient Properties: Directional Migration, Oblique Rebound, and Reduced Contact Time. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:10804-10813. [PMID: 38723143 DOI: 10.1021/acs.langmuir.4c01257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Efficiently regulating the rebound behavior of droplets post-impact is crucial for various fields, mainly including the development of self-cleaning applications, the design of surface functional materials, and the advancement of industrial techniques. By performing molecular dynamics simulations, we investigated the impact and jumping behavior of droplets on heterogeneous substrates with different wetting regions. We found that, during the impacting evolution process, the retracted droplets would move toward regions with stronger wettability due to the unbalanced force caused by the wettability difference, revealing the directional migration ability. The values of the wettability difference strongly affect the degree of oblique rebound and contact time when droplets can jump off the substrate. We then designed the surfaces with a wettability gradient and found that the oblique rebound angle could be well controlled and the contact time further reduced. Our findings may provide valuable insight into the relationship between the wettability gradient and the behavior of liquid droplets on surfaces, with broad implications for various fields such as surface engineering, materials science, microfluidics, etc.
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Affiliation(s)
- Tao Li
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China
| | - Shuyong Liang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
| | - Zhichao Li
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
| | - Jianqiang Bi
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, 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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3
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Chang LH, Kumar S. Capillary Filling in Open Rectangular Microchannels with a Spatially Varying Contact Angle. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:18526-18536. [PMID: 38054451 DOI: 10.1021/acs.langmuir.3c02865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Capillary flow in microchannels is important for many technologies, such as microfluidic devices, heat exchangers, and fabrication of printed electronics. Due to a readily accessible interior, open rectangular microchannels are particularly attractive for these applications. Here, we develop modifications of the Lucas-Washburn model to explore how a spatially varying contact angle influences capillary flow in open rectangular microchannels. Four cases are considered: (i) different uniform contact angles on channel sidewalls and channel bottom, (ii) contact angles varying along the channel cross section, (iii) contact angle varying monotonically along the channel length, and (iv) contact angle varying periodically along the channel length. For case (i), it is found that the maximum filling velocity is more sensitive to changes in the wall contact angle. For case (ii), the contact angles can be averaged to transform the problem into that of case (i). For case (iii), the time evolution of the meniscus position no longer follows the simple square-root law at short times. Finally, for case (iv), the problem is well described by using a uniform contact angle that is a suitable average. These results provide insights into how to design contact-angle variations to control capillary filling and into the influence of naturally occurring contact-angle variations on capillary flow.
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Affiliation(s)
- Li-Hsuan Chang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Satish Kumar
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Hu Z, Chu F, Shan H, Wu X, Dong Z, Wang R. Understanding and Utilizing Droplet Impact on Superhydrophobic Surfaces: Phenomena, Mechanisms, Regulations, Applications, and Beyond. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2310177. [PMID: 38069449 DOI: 10.1002/adma.202310177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 11/13/2023] [Indexed: 12/19/2023]
Abstract
Droplet impact is a ubiquitous liquid behavior that closely tied to human life and production, making indispensable impacts on the big world. Nature-inspired superhydrophobic surfaces provide a powerful platform for regulating droplet impact dynamics. The collision between classic phenomena of droplet impact and the advanced manufacture of superhydrophobic surfaces is lighting up the future. Accurately understanding, predicting, and tailoring droplet dynamic behaviors on superhydrophobic surfaces are progressive steps to integrate the droplet impact into versatile applications and further improve the efficiency. In this review, the progress on phenomena, mechanisms, regulations, and applications of droplet impact on superhydrophobic surfaces, bridging the gap between droplet impact, superhydrophobic surfaces, and engineering applications are comprehensively summarized. It is highlighted that droplet contact and rebound are two focal points, and their fundamentals and dynamic regulations on elaborately designed superhydrophobic surfaces are discussed in detail. For the first time, diverse applications are classified into four categories according to the requirements for droplet contact and rebound. The remaining challenges are also pointed out and future directions to trigger subsequent research on droplet impact from both scientific and applied perspectives are outlined. The review is expected to provide a general framework for understanding and utilizing droplet impact.
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Affiliation(s)
- Zhifeng Hu
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - He Shan
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xiaomin Wu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China
| | - Zhichao Dong
- CAS Key Laboratory of Bio-inspired Materials and Interfacial Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ruzhu Wang
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
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Zhou Y, Ding T, Cheng Y, Huang Y, Wang W, Yang J, Xie L, Ho GW, He J. Non-planar dielectrics derived thermal and electrostatic field inhomogeneity for boosted weather-adaptive energy harvesting. Natl Sci Rev 2023; 10:nwad186. [PMID: 37565206 PMCID: PMC10411684 DOI: 10.1093/nsr/nwad186] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 06/05/2023] [Accepted: 06/25/2023] [Indexed: 08/12/2023] Open
Abstract
Weather-adaptive energy harvesting of omnipresent waste heat and rain droplets, though promising in the field of environmental energy sustainability, is still far from practice due to its low electrical output owing to dielectric structure irrationality and unscalability. Here we present atypical upcycling of ambient heat and raindrop energy via an all-in-one non-planar energy harvester, simultaneously increasing solar pyroelectricity and droplet-based triboelectricity by two-fold, in contrast to conventional counterparts. The delivered non-planar dielectric with high transmittance confines the solar irradiance onto a focal hotspot, offering transverse thermal field propagation towards boosted inhomogeneous polarization with a generated power density of 6.1 mW m-2 at 0.2 sun. Moreover, the enlarged lateral surface area of curved architecture promotes droplet spreading/separation, thus travelling the electrostatic field towards increased triboelectricity. These enhanced pyroelectric and triboelectric outputs, upgraded with advanced manufacturing, demonstrate applicability in adaptive sustainable energy harvesting on sunny, cloudy, night, and rainy days. Our findings highlight a facile yet efficient strategy, not only for weather-adaptive environmental energy recovery but also in providing key insights for spatial thermal/electrostatic field manipulation in thermoelectrics and ferroelectrics.
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Affiliation(s)
- Yi Zhou
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117581, Singapore
| | - Tianpeng Ding
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117581, Singapore
- School of Electronic Science and Engineering, State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Yin Cheng
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117581, Singapore
| | - Yi Huang
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wu Wang
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jianmin Yang
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Lin Xie
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Ghim Wei Ho
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117581, Singapore
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore 138634, Singapore
| | - Jiaqing He
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, China
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Steerable directional bouncing and contact time reduction of impacting droplets on superhydrophobic stepped surfaces. J Colloid Interface Sci 2023; 629:1032-1044. [DOI: 10.1016/j.jcis.2022.09.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 08/25/2022] [Accepted: 09/04/2022] [Indexed: 11/19/2022]
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7
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Shu Y, Chu F, Hu Z, Gao J, Wu X, Dong Z, Feng Y. Superhydrophobic Strategy for Nature-Inspired Rotating Microfliers: Enhancing Spreading, Reducing Contact Time, and Weakening Impact Force of Raindrops. ACS APPLIED MATERIALS & INTERFACES 2022; 14:57340-57349. [PMID: 36512411 DOI: 10.1021/acsami.2c16662] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Wind-dispersal of seeds is a remarkable strategy in nature, enlightening the construction of microfliers for environmental monitoring. However, the flight of these microfliers is greatly affected by climatic conditions, especially in rainy days, they suffer serious raindrop impact. Here, a hierarchical superhydrophobic surface is fabricated and a novel strategy is demonstrated that the superhydrophobic coating can enhance spreading while reduce contact time and impact force of raindrops, all of which are beneficial for the rotating microfliers. When the surface rotating speed exceeds a critical value, the effect of centrifugal force becomes considerable so that the droplet spreading is enhanced. The rotating superhydrophobic surface can rotate an impacting droplet by the tangential drag force from the air boundary layer, and the rotation of the droplet generates a negative pressure zone inside it, reducing the contact time by more than 30%. The impact force by the droplet on the rotating superhydrophobic surface also has a remarkable reduction of 53% compared to that on unprocessed hydrophilic surfaces, which helps maintain the flight stability of the microfliers. This work pioneers in revealing the droplet impact effect on rotating microflier surfaces and demonstrates the effectiveness of protecting microfliers with superhydrophobic coatings, which shall guide the manufacture and flight of microfliers in rainy conditions.
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Affiliation(s)
- Yifu Shu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
| | - Zhifeng Hu
- Department of Energy and Power Engineering, Tsinghua University, Beijing100084, China
| | - Jie Gao
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
| | - Xiaomin Wu
- Department of Energy and Power Engineering, Tsinghua University, Beijing100084, China
| | - Zhichao Dong
- CAS Key Laboratory of Bio-Inspired Materials and Interfacial Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing100190, China
| | - Yanhui Feng
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
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8
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Xiao L, Pan RZ, Wu SY. Thermo-hydrodynamics of multiple drops impinging simultaneously on the grooved tubular surface and smooth cylindrical surface with different wettabilities. ANN NUCL ENERGY 2022. [DOI: 10.1016/j.anucene.2022.109398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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Yang K, Liu Q, Lin Z, Liang Y, Liu C. Bouncing dynamics of impact droplets on bioinspired surfaces with mixed wettability and directional transport control. J Colloid Interface Sci 2022; 626:193-207. [DOI: 10.1016/j.jcis.2022.06.158] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 06/09/2022] [Accepted: 06/27/2022] [Indexed: 11/25/2022]
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10
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Wu L, Guo Z, Liu W. Surface behaviors of droplet manipulation in microfluidics devices. Adv Colloid Interface Sci 2022; 308:102770. [PMID: 36113310 DOI: 10.1016/j.cis.2022.102770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/30/2022] [Accepted: 08/31/2022] [Indexed: 11/01/2022]
Abstract
In recent years, the rapid development of microfluidic technology has caused a revolutionary impact in the fields of chemistry, medicine, and life sciences. Also, droplet control is one of the most important technologies in the field of microfluidics. In order to achieve different degrees of droplet transport, the dynamic balance of the competing processes of droplet driving force and fluid resistance should be controlled to achieve good selectivity of droplet transport. Here, we focus on the principles of droplet transport in microfluidic devices, including the driving forces for droplet transport in fluids and the effects of transport properties on droplet transport. After that, the effects of external fields on the directional transport of droplets and the advantages and disadvantages of each external field in droplet transport are discussed in detail. Finally, the applications and challenges of droplet microfluidics in chemical, biomedical, and mechanical systems are comprehensively introduced.
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Affiliation(s)
- Linshan Wu
- Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062, People's Republic of China
| | - Zhiguang Guo
- Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan 430062, People's Republic of China; State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China.
| | - Weimin Liu
- 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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11
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Hu Z, Ding S, Zhang X, Wu X. Dynamic behavior and maximum width of impact droplets on single-pillar superhydrophobic surfaces. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129355] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Han X, Li J, Tang X, Li W, Zhao H, Yang L, Wang L. Droplet Bouncing: Fundamentals, Regulations, and Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2200277. [PMID: 35306734 DOI: 10.1002/smll.202200277] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/13/2022] [Indexed: 06/14/2023]
Abstract
Droplet impact is a ubiquitous phenomenon in nature, daily life, and industrial processes. It is thus crucial to tune the impact outcomes for various applications. As a special outcome of droplet impact, the bouncing of droplets keeps the form of the droplets after the impact and minimizes the energy loss during the impact, being beneficial in many applications. A unified understanding of droplet bouncing is in high demand for effective development of new techniques to serve applications. This review shows the fundamentals, regulations, and applications of millimeter-sized droplet bouncing on solid surfaces and same/miscible liquids (liquid pool and another droplet). Regulation methods and current applications are summarized, and potential directions are proposed.
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Affiliation(s)
- Xing Han
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
| | - Jiaqian Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
| | - Xin Tang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
| | - Wei Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
| | - Haibo Zhao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
- Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Ling Yang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, Hong Kong
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13
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Tsao HK, Walker GC. Virtual Issue: Wettability Gradient Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:603-604. [PMID: 35038869 DOI: 10.1021/acs.langmuir.1c02940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
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14
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Zhu P, Wang L. Microfluidics-Enabled Soft Manufacture of Materials with Tailorable Wettability. Chem Rev 2021; 122:7010-7060. [PMID: 34918913 DOI: 10.1021/acs.chemrev.1c00530] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Microfluidics and wettability are interrelated and mutually reinforcing fields, experiencing synergistic growth. Surface wettability is paramount in regulating microfluidic flows for processing and manipulating fluids at the microscale. Microfluidics, in turn, has emerged as a versatile platform for tailoring the wettability of materials. We present a critical review on the microfluidics-enabled soft manufacture (MESM) of materials with well-controlled wettability and their multidisciplinary applications. Microfluidics provides a variety of liquid templates for engineering materials with exquisite composition and morphology, laying the foundation for precisely controlling the wettability. Depending on the degree of ordering, liquid templates are divided into individual droplets, one-dimensional (1D) arrays, and two-dimensional (2D) or three-dimensional (3D) assemblies for the modular fabrication of microparticles, microfibers, and monolithic porous materials, respectively. Future exploration of MESM will enrich the diversity of chemical composition and physical structure for wettability control and thus markedly broaden the application horizons across engineering, physics, chemistry, biology, and medicine. This review aims to systematize this emerging yet robust technology, with the hope of aiding the realization of its full potential.
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Affiliation(s)
- Pingan Zhu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
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15
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Fast droplet bouncing induced by asymmetric spreading on concave superhydrophobic surfaces. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126588] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Hu Z, Zhang X, Gao S, Yuan Z, Lin Y, Chu F, Wu X. Axial spreading of droplet impact on ridged superhydrophobic surfaces. J Colloid Interface Sci 2021; 599:130-139. [PMID: 33933788 DOI: 10.1016/j.jcis.2021.04.078] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/16/2021] [Accepted: 04/16/2021] [Indexed: 12/17/2022]
Abstract
HYPOTHESIS Due to the complex hydrodynamics of droplet impact on ridged superhydrophobic surfaces, quantitative droplet spreading characteristics are unrevealed, limiting the practical applications of ridged superhydrophobic surfaces. During droplet impacting, the size ratio (the ratio of the ridge diameter to the droplet diameter) is an important factor that affects droplet spreading dynamics. EXPERIMENTS We fabricated ridged superhydrophobic surfaces with size ratios ranging from zero to one, and conduct water droplet impact experiments on these surfaces at varied Weber numbers. Aided by the numerical simulations and theoretical analysis, we illustrate the droplet spreading dynamics and reveal the law on the maximum axial spreading coefficient. FINDS The results show that the droplet spreading and retraction dynamics on ridged superhydrophobic surfaces are significantly asymmetric in the axial and spanwise directions. Focusing on the maximum axial spreading coefficient, we find it decreases first and then increases with increasing size ratios, indicating the existence of the critical size ratio. The maximum axial spreading coefficient can be reduced by 25-40% at the critical size ratio compared with that on flat surfaces. To predict the maximum axial spreading coefficient, two theoretical models are proposed respectively for size ratios smaller and larger than the critical size ratio.
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Affiliation(s)
- Zhifeng Hu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Xuan Zhang
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Sihang Gao
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Zhiping Yuan
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Yukai Lin
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China.
| | - Xiaomin Wu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China.
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17
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Zhang T, Wu J, Lin X. Lateral motion of a droplet impacting on a wettability-patterned surface: numerical and theoretical studies. SOFT MATTER 2021; 17:724-737. [PMID: 33220671 DOI: 10.1039/d0sm01858a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Surfaces with nonuniform wettability have attracted much attention recently due to their academic significance and applications in droplet lateral motion. In this study, numerical simulations and theoretical analyses are conducted to investigate the dynamic behaviors of a droplet impacting on a wettability-patterned surface, in which the superhydrophobic substrate is decorated with a hydrophilic pattern. An improved diffuse interface method coupled with the adaptive mesh-refinement technique and Kistler dynamic contact angle model is adopted to capture the interfacial evolution. After the validation of the numerical method, the dynamic mechanisms of impacting droplets are explored by analyzing the variation of the contact line and velocity profile. Then, systematic simulations are conducted using hydrophilic patterns with different geometric parameters. And the parameter of effective retraction area S is introduced to quantify the wettability patterns. On this basis, the general rules between the patterns and droplet lateral motion are established, and the design principles of hydrophilic patterns are obtained. The numerical results indicate that arc-shape hydrophilic patterns are more appropriate for realizing the droplet lateral motion, which can produce a larger lateral velocity and less residual liquid. In addition, the relevant motion parameters of the droplet are predicted more accurately by using the previous theoretical method. And the mechanism of energy transformation and dissipation is further revealed. Moreover, a simple and practical model is proposed to predict the lateral velocity using the effective retraction area.
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Affiliation(s)
- Tongwei Zhang
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China. and Department of Aerodynamics, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China and Key Laboratory of Unsteady Aerodynamics and Flow Control, Ministry of Industry and Information Technology, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China
| | - Jie Wu
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China. and Department of Aerodynamics, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China and Key Laboratory of Unsteady Aerodynamics and Flow Control, Ministry of Industry and Information Technology, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China and Key Laboratory of Icing and Anti/De-icing, China Aerodynamics Research and Development Center, South Second Ring Road 6, Mianyang, Sichuan 621000, China
| | - Xingjian Lin
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China. and Department of Aerodynamics, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China and Key Laboratory of Unsteady Aerodynamics and Flow Control, Ministry of Industry and Information Technology, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China
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18
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Zhu P, Chen C, Nandakumar K, Wang L. Nonspecular Reflection of Droplets. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2006695. [PMID: 33345437 DOI: 10.1002/smll.202006695] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Indexed: 06/12/2023]
Abstract
The bouncing of droplets on super-repellent surfaces normally resembles specular reflection that obeys the law of reflection. Here, the nonspecular reflection of droplet impingement onto solid surfaces with a dimple for energy-efficient, omnidirectional droplet transport is reported. With the dimple of the radius being comparable to that of the droplet, all the symmetries in the law of reflection can be broken down so that the droplet is endowed with a translational velocity finely tunable in both its direction and magnitude simply by varying the radii of the droplet and the dimple, the impinging position, and droplet Weber number. Tailoring the initial and translational velocity of impinging droplets would steer their reflected trajectories at will, thus enabling versatile droplet manipulation including trapping, shedding, antigravity transport, targeted positioning, and on-demand coalescence of droplets.
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Affiliation(s)
- Pingan Zhu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
- HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), Hangzhou, Zhejiang, 311300, China
| | - Chengmin Chen
- Energy Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, Shandong, 250014, China
- School of Energy and Power Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan, Shandong, 250014, China
| | - Krishnaswamy Nandakumar
- Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), Hangzhou, Zhejiang, 311300, China
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19
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Yan X, Qin Y, Chen F, Zhao G, Sett S, Hoque MJ, Rabbi KF, Zhang X, Wang Z, Li L, Chen F, Feng J, Miljkovic N. Laplace Pressure Driven Single-Droplet Jumping on Structured Surfaces. ACS NANO 2020; 14:12796-12809. [PMID: 33052666 DOI: 10.1021/acsnano.0c03487] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Droplet transport on, and shedding from, surfaces is ubiquitous in nature and is a key phenomenon governing applications including biofluidics, self-cleaning, anti-icing, water harvesting, and electronics thermal management. Conventional methods to achieve spontaneous droplet shedding enabled by surface-droplet interactions suffer from low droplet transport velocities and energy conversion efficiencies. Here, by spatially confining the growing droplet and enabling relaxation via rationally designed grooves, we achieve single-droplet jumping of micrometer and millimeter droplets with dimensionless jumping velocities v* approaching 0.95, significantly higher than conventional passive approaches such as coalescence-induced droplet jumping (v* ≈ 0.2-0.3). The mechanisms governing single-droplet jumping are elucidated through the study of groove geometry and local pinning, providing guidelines for optimized surface design. We show that rational design of grooves enables flexible control of droplet-jumping velocity, direction, and size via tailoring of local pinning and Laplace pressure differences. We successfully exploit this previously unobserved mechanism as a means for rapid removal of droplets during steam condensation. Our study demonstrates a passive method for fast, efficient, directional, and surface-pinning-tolerant transport and shedding of droplets having micrometer to millimeter length scales.
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Affiliation(s)
- Xiao Yan
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yimeng Qin
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Feipeng Chen
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Guanlei Zhao
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Soumyadip Sett
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Muhammad Jahidul Hoque
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Kazi Fazle Rabbi
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Xueqian Zhang
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Zi Wang
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Longnan Li
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Feng Chen
- Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China
| | - Jie Feng
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Nenad Miljkovic
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
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