1
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Zhao J, Sun R, Liu C, Mo J. Application of ZnO/epoxy resin superhydrophobic coating for buoyancy enhancement and drag reduction. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129714] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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2
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Camalan M, Arol Aİ. Forming superhydrophobic surfaces for mineral separation at water pulsating jigs. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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3
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Sun P, Feng X, Tian G, Zhang X, Chu J. Ultrafast Self-Healing Superhydrophobic Surface for Underwater Drag Reduction. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:10875-10885. [PMID: 36001007 DOI: 10.1021/acs.langmuir.2c01566] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The self-healing superhydrophobic surfaces have attracted great interest owing to restoring superhydrophobicity without preparation crafts. However, the self-healing superhydrophobic surface still faces the dilemma of long repairing time. Especially in aqueous environments, superhydrophobic surfaces are highly susceptible to contamination and damage. In the current study, a superhydrophobic surface with ultrafast repairability was developed, which apply for drag reduction in aqueous medium. The prepared superhydrophobic surface can recover superhydrophobicity in only 30 s after severe physical and chemical damage. In addition, this research pioneered the combination of superhydrophobicity and porous structures for underwater drag reduction. The study of drag reduction confirms that the superhydrophobic surface can reduce the frictional drag by about 43% in the water. However, the drag reduction rate of the superhydrophobic surface with the porous structure can be improved to 76% due to increased stability of the air layer. More importantly, the porous structure with the average pore size of 50 μm has the most excellent stability through further experiments on the underwater air layer. This is attributed to the proper size of the pore to effectively balance the capillary force and resist wetting in the marginal region. This study will bring inspiration for the large-scale application of superhydrophobic surfaces and long-term drag reduction.
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Affiliation(s)
- Pengfei Sun
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Xiaoming Feng
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Guizhong Tian
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Xiaowei Zhang
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Jiahui Chu
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
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4
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Hydrodynamic collisions involving bubbles and mineral particles. CAN J CHEM ENG 2021. [DOI: 10.1002/cjce.24347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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5
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Vakarelski IU, Kamoliddinov F, Jetly A, Thoroddsen ST. When superhydrophobicity can be a drag: Ventilated cavitation and splashing effects in hydrofoil and speed-boat models tests. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127344] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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6
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Yao C, Zhou Y, Wang J, Jiang L. Bioinspired Universal Approaches for Cavity Regulation during Cylinder Impact Processes for Drag Reduction in Aqueous Media: Macrogeometry Vanquishing Wettability. ACS APPLIED MATERIALS & INTERFACES 2021; 13:38808-38815. [PMID: 34347428 DOI: 10.1021/acsami.1c06846] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Stabilizing lubricating gas films at the solid-liquid interface is a promising strategy for underwater drag reduction. It has been restricted by the enormous extra energy input and the poor stability of superhydrophobic coatings. Cavity encapsulation is a valid method to improve and maintain the formation of the air layer on the solid surface, which is created by the rapidly impacting process on a water surface. The wettability of solid objects (the combination of the surface roughness and chemical component) and liquid properties played a key factor in determining the water impact process for cavity entrainment. However, inspired by the striking behavior of basilisk lizards and their toe's shape, we found that the geometric shape of solid objects plays an equally important role in cavity entrainment and stabilization, which is often ignored. Herein, we present a universal strategy to retain the air cavity on the cylinder surfaces. The cavity can be retained not only on the surface of superhydrophobic cylinders but also on the surface of hydrophobic, hydrophilic, and even superhydrophilic cylinders, without bursting at a depth of 70.0-90.0 cm underwater. The retaining cavity enfolds the profile and upper sides of the cylinder and changes its shape to a streamlined body to achieve underwater drag reduction. In addition, optimizing the cylinders' shapes by increasing the fillet radii significantly improved the drag reduction efficiency from 64.2 to 70.5%.
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Affiliation(s)
- Changzhuang Yao
- CAS Key Laboratory of Bio-inspired Materials and Interface Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 101407, P. R. China
| | - Yanjiao Zhou
- Beijing E-town Experimental Primary School, Beijing 100176, P. R. China
| | - Jingming Wang
- School of Materials Science and Technology, Beijing University of Chemical Technology, Beijing 100029, P. R. China
| | - Lei Jiang
- CAS Key Laboratory of Bio-inspired Materials and Interface Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 101407, P. R. China
- School of Chemistry, Beihang University, Beijing 100191, P. R. China
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7
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Zhu Y, Yang F, Guo Z. Bioinspired surfaces with special micro-structures and wettability for drag reduction: which surface design will be a better choice? NANOSCALE 2021; 13:3463-3482. [PMID: 33566874 DOI: 10.1039/d0nr07664c] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Human beings learn from creatures in nature and imitate them to solve challenges in daily life. Thus, the use of bioinspired surfaces for drag reduction has attracted extensive attention in recent years due to their important applications in many fields, such as pipeline systems, maritime transportation, and military weapons. Herein, we introduce some typical plants and animals with low drag surfaces that exist in nature, focusing on their drag reduction patterns. There are two main mechanisms to explain how surfaces reduce frictional drag, where one is to design a suitable surface geometry to change the flow distribution of surrounding fluid and the other is to introduce a low friction lubricating layer (usually air or non-toxic silicone oil) to partially or completely replace the solid-liquid interface. Hence, by mimicking these organisms, some surfaces have been fabricated to reduce frictional drag, including riblets, superhydrophobic surfaces, and slippery liquid-infused porous surfaces. With the increasing research on drag-reducing surfaces, the drag reduction rate of different types of surface designs has greatly improved in recent years. This review provides a holistic overview that facilitates direct comparisons between these surface types. To select an optimal surface for drag reduction in practical applications, the merits and deficiencies of different surface designs are analysed and compared. Finally, based on the current challenges, we present some future prospects for the application of bioinspired surfaces in drag reduction.
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Affiliation(s)
- Yi Zhu
- Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science & Engineering and Hubei Key Laboratory of Polymer Materials, Hubei University, Wuhan 430062, China.
| | - Fuchao Yang
- Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science & Engineering and Hubei Key Laboratory of Polymer Materials, Hubei University, Wuhan 430062, China.
| | - Zhiguang Guo
- Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science & Engineering and Hubei Key Laboratory of Polymer Materials, Hubei University, Wuhan 430062, China. and State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
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8
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Yao C, Zhang J, Xue Z, Yu K, Yu X, Yang X, Qu Q, Gan W, Wang J, Jiang L. Bioinspired Cavity Regulation on Superhydrophobic Spheres for Drag Reduction in an Aqueous Medium. ACS APPLIED MATERIALS & INTERFACES 2021; 13:4796-4803. [PMID: 33448779 DOI: 10.1021/acsami.0c20073] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Hydrodynamic drag not only results in high-energy consumption for water vehicles but also impedes the increase of vehicle speed. The introduction of a low-viscosity gas lubricating film is assumed to be an effective and promising method to reduce hydrodynamic drag. However, the poor stability of the gas film and massive extra energy consumption restricts the practical application of the gas lubricating method. Herein, inspired by the microhairs with low surface energy wax covering the abdomen of water spiders, superhydrophobic sphere surfaces were designed. Attributed to numerous neighboring nanoneedle branches with low surface energy chemicals, an air-entrained cavity with a large surface area was captured and stabilized by the superhydrophobic sphere, changing its shape from a sphere to a streamlined body. The cavity continued attaching to the superhydrophobic sphere without bursting at a depth of 70.0-90.0 cm underwater and reduced the hydrodynamic drag by more than 90%. This work provides a simple, cost-effective, and energy-efficient way to stabilize the underwater gas-liquid interface to achieve a reduction in the hydrodynamic drag.
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Affiliation(s)
- Changzhuang Yao
- CAS Key Laboratory of Bio-inspired Materials and Interface Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Future Technology College, University of Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Jingjing Zhang
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
- BAIC Motor Corporation Ltd., Beijing 101300, P. R. China
| | - Zihan Xue
- Key Laboratory of Advanced Technology of Intelligent Unmanned Flight System of Ministry of Industry and Information Technology, Beihang University, Beijing 100191, P. R. China
| | - Kang Yu
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
| | - Xinping Yu
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, P. R. China
| | - Xiaoxiao Yang
- Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, P. R. China
| | - Qiulin Qu
- School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, P. R. China
| | - Wenbiao Gan
- Key Laboratory of Advanced Technology of Intelligent Unmanned Flight System of Ministry of Industry and Information Technology, Beihang University, Beijing 100191, P. R. China
| | - Jingming Wang
- School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China
| | - Lei Jiang
- CAS Key Laboratory of Bio-inspired Materials and Interface Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Future Technology College, University of Chinese Academy of Sciences, Beijing 100190, P. R. China
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9
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Jiang S, Hu Y, Wu H, Li R, Zhang Y, Chen C, Xue C, Xu B, Zhu W, Li J, Wu D, Chu J. Three-Dimensional Multifunctional Magnetically Responsive Liquid Manipulator Fabricated by Femtosecond Laser Writing and Soft Transfer. NANO LETTERS 2020; 20:7519-7529. [PMID: 32915586 DOI: 10.1021/acs.nanolett.0c02997] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Nature-inspired magnetically responsive intelligent topography surfaces have attracted considerable attention owing to their controllable droplet manipulation abilities. However, it is still challenging for magnetically responsive surfaces to realize three-dimensional (3D) droplet/multidroplet transport in both horizontal and vertical directions. Additionally, the droplet horizontal propulsion speed needs to be improved. In this work, a 3D droplet/multidroplet transport strategy based on magnetically responsive microplates array (MMA) actuated by a spatially varying and periodic magnetic field is proposed. The modified superhydrophobic surface can transport droplets rapidly both in horizontal and vertical directions, and it can even realize against-gravity upslope propulsion. The rapid horizontal droplet propulsion (∼58.6 mm/s) is ascribed to the abrupt inversion of the modified surface induced by the specific magnetic field. Furthermore, the nonmagnetically responsive microplates (NMMs)/MMA composite surface is constructed to realize 3D multidroplet manipulation. The implementations of MMA in manipulation of continuous fluids and liquid metal are further demonstrated, providing a valuable platform for microfluidic applications.
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Affiliation(s)
- Shaojun Jiang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Yanlei Hu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Hao Wu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Rui Li
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Yiyuan Zhang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Chao Chen
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Cheng Xue
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Bing Xu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Wulin Zhu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Jiawen Li
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Dong Wu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
| | - Jiaru Chu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, China
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10
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Vakarelski IU, Jetly A, Thoroddsen ST. Stable-streamlined cavities following the impact of non-superhydrophobic spheres on water. SOFT MATTER 2019; 15:6278-6287. [PMID: 31322158 DOI: 10.1039/c9sm01025d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The formation of a stable-streamlined gas cavity following the impact of a heated Leidenfrost sphere on a liquid surface or a superhydrophobic sphere on water is a recently demonstrated phenomenon. A sphere encapsulated in a teardrop-shaped gas cavity was found to have near-zero hydrodynamic drag due to the self-adjusting streamlined shape and the free-slip boundary condition on the cavity interface. Here we show that such cavities can as well be formed following water impact from a sufficient height of non-superhydrophobic spheres with water contact angles between >30° and 120°. In this case the streamlined cavity is attached just above the sphere's equator, instead of entirely wrapping the sphere. Nevertheless, this sphere with attached cavity formation has near-zero drag and a predetermined free fall velocity in compliance with the Bernoulli law of potential flow. The effect of surfactant addition to the water solution is investigated. The shape and fall velocity of a sphere with streamlined cavity formation were unaffected by the addition of low surface modulus synthetic surfactants, but were destabilised when solutions containing high surface modulus surfactants, such as soaps, were used.
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Affiliation(s)
- Ivan U Vakarelski
- Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
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11
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Tian C, Wang X, Liu Y, Yang W, Hu H, Pei X, Zhou F. In Situ Grafting Hydrophilic Polymeric Layer for Stable Drag Reduction. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:7205-7211. [PMID: 31083953 DOI: 10.1021/acs.langmuir.9b00321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Developing drag reduction techniques has attracted great attention because of their need in practical applications. However, many of the proposed strategies exhibit some inevitable limitations, especially for long period of adhibition. In this work, the dynamic but stable drag reduction effect of superhydrophilic hydrogel-coated iron sphere falling freely in a cylindrical water tank was investigated. The absolute instantaneous velocities and displacements of either the hydrogel-encapsulated or unmodified iron sphere falling freely in water were monitored via a high-speed video. It was revealed that, in the range of Reynolds number from 104 to 106, the optimized hydrogel-coated iron sphere with uniform stability could reduce the resistance by up to 40%, which was mainly due to the boundary slip of water and the delayed boundary separation that resulted from the coated hydrogel. Besides, the deliberate experiments and analysis further indicated that the superhydrophilic hydrogel layer accompanied by the emergence of the drag crisis has largely effected the distribution of flow field at the boundary around the sphere. More importantly, the drag reduction behavior based on the proposed method was thermodynamically stable and resistant to external stimulus, including fluidic oscillator and hydrodynamic pressure. The effective long-term drag reduction performance of the hydrophilic substrate can be expected, correspondingly, and also provides a novel preliminary protocol and avenues for the development of durable drag reduction technologies.
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Affiliation(s)
- Chaoguo Tian
- School of Mechatronics Engineering , Nanchang University , Nanchang 330031 , China
| | | | - Ying Liu
- School of Mechatronics Engineering , Nanchang University , Nanchang 330031 , China
| | - Wufang Yang
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics , Chinese Academy of Sciences , Tianshui Middle Rd , Lanzhou 730000 , China
| | | | | | - Feng Zhou
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics , Chinese Academy of Sciences , Tianshui Middle Rd , Lanzhou 730000 , China
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12
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Jiang S, Hu Y, Wu H, Zhang Y, Zhang Y, Wang Y, Zhang Y, Zhu W, Li J, Wu D, Chu J. Multifunctional Janus Microplates Arrays Actuated by Magnetic Fields for Water/Light Switches and Bio-Inspired Assimilatory Coloration. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1807507. [PMID: 30721548 DOI: 10.1002/adma.201807507] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/16/2019] [Indexed: 05/21/2023]
Abstract
Smart dynamic regulation structured surfaces, inspired by nature, which can dynamically change their surface topographies under external stimuli for convertible fluidic and optical properties, have recently motivated significant interest for scientific research and industrial applications. However, there is still high demand for the development of multifunctional dynamically transformable surfaces using facile preparation strategies. In this work, a type of Janus high-aspect-ratio magnetically responsive microplates array (HAR-MMA) is readily fabricated by integrating a flexible laser scanning strategy, smart shape-memory-polymer-based soft transfer, and a simple surface treatment. By applying external magnetic field, instantaneous and reversible deformation of Janus HAR-MMA can be actuated, so surface wettability can be reversibly switched between superhydrophobic (158°) and hydrophilic (40°) states, based on which a novel magnetically responsive water droplet switch can be realized. Moreover, inspired by the biological assimilatory coloration of chameleons, dynamically color conversion can be skillfully realized by applying different colors on each side of the Janus HAR-MMA. Finally, as a proof-of-concept demonstration in light manipulation, a HAR-MMA is applied as an optical shutter actuated by external magnetic field with eximious controllability and repeatability. The developed multifunctional HAR-MMA provides a versatile platform for microfluidic, biomedical, and optical applications.
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Affiliation(s)
- Shaojun Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Yanlei Hu
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Hao Wu
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Yachao Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Yiyuan Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Yulong Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Yinghui Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Wulin Zhu
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Jiawen Li
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Dong Wu
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
| | - Jiaru Chu
- Hefei National Laboratory for Physical Sciences at the Microscale and CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, 230027, China
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Di Mundo R, Bottiglione F, Pascazio G, Carbone G. Water entry and fall of hydrophobic and superhydrophobic Teflon spheres. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:445001. [PMID: 30222133 DOI: 10.1088/1361-648x/aae1dd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Hydrophobic and superhydrophobic solid Teflon spheres have been observed while settling in water under the action of gravity, starting from different initial conditions, and have been followed until the steady-state is reached. The superhydrophobic sphere features a nano/microtextured surface and advancing and receding water contact angles equal to, respectively, [Formula: see text] and [Formula: see text]. When impacting water from air, both spheres can entrap a conspicuous amount of air deriving from the sealing of a macro-sized air cavity formed upon impact (air cavity trapping) and standing at the rear part of the settling sphere. It is shown that this air amount, like a spindle, reduces the force coefficient exerted on the sphere, basically acting on the pressure drag. However, the air cavity trapping occurs above a critical impact velocity which for the superhydrophobic spheres is significantly lower than that pertaining to the hydrophobic one; thus a certain range of impact velocities exists at which the superhydrophobic sphere experiences a lower pressure drag and a higher mean velocity. As soon as the air cavity vanishes, the dynamics of the superhydrophobic sphere becomes indistinguishable from that of the hydrophobic one, in spite of the persistence of air within the surface micro-texture.
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Affiliation(s)
- R Di Mundo
- Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica (DICATECh), Politecnico di Bari, via Orabona 4, 70126 Bari, Italy
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14
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Langley KR, Li EQ, Vakarelski IU, Thoroddsen ST. The air entrapment under a drop impacting on a nano-rough surface. SOFT MATTER 2018; 14:7586-7596. [PMID: 30069555 DOI: 10.1039/c8sm01070f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We study the impact of drops onto a flat surface with a nano-particle-based superhydrophobic coating, focusing on the earliest contact using 200 ns time-resolution. A central air-disc is entrapped when the drop impacts the surface, and when the roughness is appropriately accounted for, the height and radial extent of the air-disc follow the scaling laws established for impacts onto smooth surfaces. The roughness also modifies the first contact of the drop around the central air-disc, producing a thick band of micro-bubbles. The initial bubbles within this band coalesce and grow in size. We also infer the presence of an air-film residing inside the microstructure, at radial distances outside the central air-disc. This is manifest by the sudden appearance of microbubbles within a few microseconds after impact. The central air-disc remains pinned on the roughness, unless it is chemically altered to make it superhydrophilic.
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Affiliation(s)
- Kenneth R Langley
- Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.
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