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Sun P, Jin Y, Yin Y, Wu C, Song C, Feng Y, Zhou P, Qin X, Niu Y, Liu Q, Zhang J, Wang Z, Hao X. Achieving Extreme Pressure Resistance to Liquids on a Super-Omniphobic Surface with Armored Reentrants. SMALL METHODS 2024; 8:e2201602. [PMID: 36919581 DOI: 10.1002/smtd.202201602] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/01/2023] [Indexed: 06/18/2023]
Abstract
Static repellency and pressure resistance to liquids are essential for high-performance super-omniphobic surfaces. However, these two merits appear mutually exclusive in conventional designs because of their conflicting structural demands: Static liquid repellency necessitates minimal solid-liquid contact, which in turn inevitably undercuts the surface's ability to resist liquid invasion exerted by the elevated pressure. Here, inspired by the Springtail, these two merits can be simultaneously realized by structuring surfaces at two size scales, with a micrometric reentrant structure providing static liquid repellency and a nanometric reentrant structure providing pressure resistance, which dexterously avoids the dilemma of their structural conflicts. The nanometric reentrants are densely packed on the micrometric ones, serving as "armor" that prevents liquids invasion by generating multilevel energy barriers, thus naming the surface as the armored reentrants (AR) surface. The AR surface could repel liquids with very low surface tensions, such as silicone oil (21 mN m-1), and simultaneously resist great pressure from the liquids, exemplified by enduring the impact of low-surface-tension liquids under a high weber number (>400), the highest-pressure resistance ever reported. With its scalable fabrication and enhanced performance, our design could extend the application scope of liquid-repellent surfaces toward ultimate industrial settings.
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Affiliation(s)
- Pengcheng Sun
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, P. R. China
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Yuankai Jin
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Yingying Yin
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Chenyang Wu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Chuanhui Song
- Department of Oral and Maxillofacial Surgery, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, 210008, P. R. China
| | - Yawei Feng
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Peiyang Zhou
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Xuezhi Qin
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Yusheng Niu
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, P. R. China
| | - Qiankai Liu
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, P. R. China
| | - Jie Zhang
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, P. R. China
| | - Zuankai Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, 999077, P. R. China
| | - Xiuqing Hao
- College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210016, P. R. China
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2
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Qiao S, Cai C, Pan C, Liu Y, Zhang Q. Study on the Performance of a Surface with Coupled Wettability Difference and Convex-Stripe Array for Improved Air Layer Stability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:4940-4952. [PMID: 38378438 DOI: 10.1021/acs.langmuir.3c03929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
The existence of an air layer reduces friction drag on superhydrophobic surfaces. Therefore, improving the air layer stability of superhydrophobic surfaces holds immense significance in reducing both energy consumption and environmental pollution caused by friction drag. Based on the properties of mathematical discretization and the contact angle hysteresis generated by the wettability difference, a surface coupled with a wettability difference treatment and a convex-stripe array is developed by laser engraving and fluorine modification, and its performance in improving the air layer stability is experimentally studied in a von Kármán swirling flow field. The results show that the destabilization of the air layer is mainly caused by the Kelvin-Helmholtz instability, which is triggered by the density difference between gas and liquid, as well as the tangential velocity difference between gas and liquid. When the air layer is relatively thin, tangential wave destabilization occurs, whereas for larger thicknesses, the destabilization mode is coupled wave destabilization. The maximum Reynolds number that keeps the air layer fully covering the surface of the rotating disk (with drag reduction performance) during the disk rotation process is defined as the critical Reynolds number (Rec), which is 1.62 × 105 for the uniform superhydrophobic surface and 3.24 × 105 for the superhydrophobic surface with a convex stripe on the outermost ring (SCSSP). Individual treatments of wettability difference and a convex-stripe array on the SCSSP further improve the air layer stability, but Rec remains at 3.24 × 105. Finally, the coupling of the wettability difference treatment with a convex-stripe array significantly improves the air layer stability, resulting in an increase of Rec to 4.05 × 105, and the drag reduction rate stably maintained around 30%.
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Affiliation(s)
- Shuai Qiao
- Key Laboratory of Fluid Mechanics of Ministry of Education, Beihang University, Beijing 100191, China
| | - Chujiang Cai
- Key Laboratory of Fluid Mechanics of Ministry of Education, Beihang University, Beijing 100191, China
- Aircraft and Propulsion Laboratory, Ningbo Institute of Technology, Beihang University, Ningbo 315100, China
| | - Chong Pan
- Key Laboratory of Fluid Mechanics of Ministry of Education, Beihang University, Beijing 100191, China
- Aircraft and Propulsion Laboratory, Ningbo Institute of Technology, Beihang University, Ningbo 315100, China
| | - Yanpeng Liu
- Key Laboratory of Fluid Mechanics of Ministry of Education, Beihang University, Beijing 100191, China
| | - Qingfu Zhang
- Key Laboratory of Fluid Mechanics of Ministry of Education, Beihang University, Beijing 100191, China
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Sun P, Hao X, Jin Y, Yin Y, Wu C, Zhang J, Gao L, Wang S, Wang Z. Heterogenous Slippery Surfaces: Enabling Spontaneous and Rapid Transport of Viscous Liquids with Viscosities Exceeding 10 000 mPa s. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2304218. [PMID: 37649201 DOI: 10.1002/smll.202304218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 08/07/2023] [Indexed: 09/01/2023]
Abstract
Superhydrophobic and slippery lubricant-infused surfaces have garnered significant attention for their potential to passively transport low-viscosity liquids like water (1 mPa s). Despite exciting progress, these designs have proven ineffective for transporting high-viscosity liquids such as polydimethylsiloxane (5500 mPa s) due to their inherent limitations imposed by the homogenous surface design, resulting in high viscous drags and compromised capillary forces. Here, a heterogenous water-infused divergent surface (WIDS) is proposed that achieves spontaneous, rapid, and long-distance transport of viscous liquids. WIDS reduces viscous drag by spatially isolating the viscous liquids and surface roughness through its heterogenous, slippery topological design, and generates capillary forces through its heterogenous wetting distributions. The essential role of surface heterogeneity in viscous liquid transport is theoretically and experimentally verified. Remarkably, such a heterogenous paradigm enables transporting liquids with viscosities exceeding 12 500 mPa s, which is two orders of magnitude higher than state-of-the-art techniques. Furthermore, this heterogenous design is generic for various viscous liquids and can be made flexible, making it promising for various systems that require viscous liquid management, such as micropatterning.
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Affiliation(s)
- Pengcheng Sun
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Xiuqing Hao
- Department of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210000, P. R. China
| | - Yuankai Jin
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Yingying Yin
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Chenyang Wu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Jie Zhang
- Department of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 210000, P. R. China
| | - Lujia Gao
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Steven Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Zuankai Wang
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, 999077, P. R. China
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4
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Dynamic evolution of oil–water interface during displacement in microcavities. Colloids Surf A Physicochem Eng Asp 2023. [DOI: 10.1016/j.colsurfa.2022.130698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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5
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Garcia-Gonzalez D, Corrales TP, Dacunzi M, Kappl M. Squeezing Drops: Force Measurements of the Cassie-to-Wenzel Transition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:14666-14672. [PMID: 36410035 DOI: 10.1021/acs.langmuir.2c02095] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Superhydrophobic surfaces have long been the center of attention of many researchers due to their unique liquid repellency and self-cleaning properties. However, these unique properties rely on the stability of the so-called Cassie state, which is a metastable state with air-filled microstructures. This state tends to transit to the stable Wenzel state, where the inside of the microstructures eventually wets. For potential industrial applications, it is therefore critical to maintain the Cassie state. We investigate the Cassie-to-Wenzel transition on superhydrophobic micropillar surfaces by squeezing a water drop between the surface and a transparent superhydrophobic force probe. The probe's transparency allows the use of top-view optics to monitor the area of the drop as it is squeezed against a micropillared surface. The impalement, or Cassie-to-Wenzel transition, is identified as a sharp decrease in force accompanied by an abrupt change in the drop's contact area. We compare the force measured by the sensor with the capillary pressure force calculated from the observed drop shape and find a good agreement between both quantities. We also study the force and pressure at impalement as a function of the pillar's slenderness ratio. Finally, we compare the impalement pressure with three literature predictions and find that our experimental values are consistently lower than the theoretical values. We find that a possible cause of this earlier Cassie-to-Wenzel transition may be the coalescence of the squeezed drop with microdroplets that nucleate around the base of the micropillars.
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Affiliation(s)
- Diana Garcia-Gonzalez
- Physics of Fluids group, Max-Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AEEnschede, Netherlands
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Tomas P Corrales
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
- Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, 2390123Valparaíso, Chile
| | - Maria Dacunzi
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128Mainz, Germany
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6
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Wang X, Fu C, Zhang C, Qiu Z, Wang B. A Comprehensive Review of Wetting Transition Mechanism on the Surfaces of Microstructures from Theory and Testing Methods. MATERIALS 2022; 15:ma15144747. [PMID: 35888211 PMCID: PMC9317979 DOI: 10.3390/ma15144747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/01/2022] [Accepted: 06/07/2022] [Indexed: 02/07/2023]
Abstract
Superhydrophobic surfaces have been widely employed in both fundamental research and industrial applications because of their self-cleaning, waterproof, and low-adhesion qualities. Maintaining the stability of the superhydrophobic state and avoiding water infiltration into the microstructure are the basis for realizing these characteristics, while the size, shape, and distribution of the heterogeneous microstructures affect both the static contact angle and the wetting transition mechanism. Here, we review various classical models of wettability, as well as the advanced models for the corrected static contact angle for heterogeneous surfaces, including the general roughness description, fractal theory description, re-entrant geometry description, and contact line description. Subsequently, we emphasize various wetting transition mechanisms on heterogeneous surfaces. The advanced testing strategies to investigate the wetting transition behavior will also be analyzed. In the end, future research priorities on the wetting transition mechanisms of heterogeneous surfaces are highlighted.
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Affiliation(s)
- Xiao Wang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
| | - Cheng Fu
- China Classification Society Quality Assurance Ltd., Beijing 100006, China;
| | - Chunlai Zhang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
| | - Zhengyao Qiu
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
| | - Bo Wang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China; (X.W.); (C.Z.); (Z.Q.)
- Correspondence:
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7
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Ryu S, Zhang H, Emeigh C. The Dark Annulus of a Drop in a Hele-Shaw Cell Is Caused by the Refraction of Light through Its Meniscus. MICROMACHINES 2022; 13:mi13071021. [PMID: 35888838 PMCID: PMC9317764 DOI: 10.3390/mi13071021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 02/01/2023]
Abstract
Knowing the meniscus shape of confined drops is important for understanding how they make first contact and then coalesce. When imaged from the top view by brightfield microscopy, a liquid drop (e.g., corn syrup) confined in a Hele-Shaw cell, surrounded by immiscible liquid (e.g., mineral oil), had a dark annulus, and the width of the annulus decreased with increasing concentration of corn syrup. Since the difference in the annulus width was presumed to be related to the meniscus shape of the drops, three-dimensional images of the drops with different concentrations were obtained using confocal fluorescence microscopy, and their cross-sectional meniscus profile was determined by image processing. The meniscus of the drops remained circular despite varying concentration. Since the refractive index of corn syrup increased with concentration, while the surface tension coefficient between corn syrup and mineral oil remained unchanged, the observed change in the annulus width was then attributed to the refraction of light passing through the drop’s meniscus. As such, a ray optics model was developed, which predicted that the annulus width of the drop would decrease as the refractive index of the drop approached that of the surrounding liquid. Therefore, the dark annulus of the drops in the Hele-Shaw cell was caused by the refraction of light passing through the circular meniscus of the drop.
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Affiliation(s)
- Sangjin Ryu
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (H.Z.); (C.E.)
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
- Correspondence:
| | - Haipeng Zhang
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (H.Z.); (C.E.)
| | - Carson Emeigh
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (H.Z.); (C.E.)
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8
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Zhang Z, Zhao M, Ahn Y, Jang J. Wettability of a surface engraved with the periodic nanoscale trenches: Effects of geometry and pressure. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116276] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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9
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Mehanna YA, Sadler E, Upton RL, Kempchinsky AG, Lu Y, Crick CR. The challenges, achievements and applications of submersible superhydrophobic materials. Chem Soc Rev 2021; 50:6569-6612. [PMID: 33889879 DOI: 10.1039/d0cs01056a] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Superhydrophobic materials have been widely reported throughout the scientific literature. Their properties originate from a highly rough morphology and inherently water repellent surface chemistry. Despite promising an array of functionalities, these materials have seen limited commercial development. This could be attributed to many factors, like material compatibility, low physical resilience, scaling-up complications, etc. In applications where persistent water contact is required, another limitation arises as a major concern, which is the stability of the air layer trapped at the surface when submerged or impacted by water. This review is aimed at examining the diverse array of research focused on monitoring/improving air layer stability, and highlighting the most successful approaches. The reported complexity of monitoring and enhancing air layer stability, in conjunction with the variety of approaches adopted, results in an assortment of suggested routes to achieving success. The review is addressing the challenge of finding a balance between maximising water repulsion and incorporating structures that protect air pockets from removal, along with challenges related to the variant approaches to testing air-layer stability across the research field, and the gap between the achieved progress and the required performance in real-life applications.
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Affiliation(s)
- Yasmin A Mehanna
- Materials Innovation Factory, Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK
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10
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Dynamics of wetting transition of initially hydrocarbon-filled microscopic cavities replaced with water. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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11
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Yu N, Kiani S, Xu M, Kim CJC. Brightness of Microtrench Superhydrophobic Surfaces and Visual Detection of Intermediate Wetting States. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:1206-1214. [PMID: 33428410 DOI: 10.1021/acs.langmuir.0c03172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
For a superhydrophobic (SHPo) surface under water, the dewetted or wetted states are easily distinguishable by the bright silvery plastron or lack of it, respectively. However, to detect an intermediate state between the two, where water partially intrudes the surface roughness, a special visualization technique has been needed. Focusing on SHPo surfaces of parallel microtrenches and considering drag reduction as a prominent application, we (i) show the reliance on surface brightness alone may seriously mislead the wetting state, (ii) theorize how the brightness is determined by water intrusion depth and viewing direction, (iii) support the theory experimentally with confocal microscopy and CCD cameras, (iv) present how to estimate the intrusion depth using optical images taken from different angles, and (v) showcase how to detect intermediate states slightly off the properly dewetted state by simply looking. The proposed method would allow monitoring SHPo trench surfaces without bulky instruments-especially useful for large samples and field tests.
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Affiliation(s)
- Ning Yu
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Sarina Kiani
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Muchen Xu
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Chang-Jin Cj Kim
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States
- Bioengineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States
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12
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Iwamatsu M. Free-energy landscapes of intrusion and extrusion of liquid in truncated and inverted truncated conical pores: Implications for the Cassie-Baxter to Wenzel transition. Phys Rev E 2020; 102:052801. [PMID: 33327066 DOI: 10.1103/physreve.102.052801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 10/20/2020] [Indexed: 11/07/2022]
Abstract
As the simplest model of transition between the superhydrophobic Cassie-Baxter (CB) and Wenzel (W) states of a macroscopic droplet sitting on a microscopically rough or corrugated substrate, a substrate whose surface is covered by identical truncated or inverted truncated conical pores is considered. The free-energy landscapes of the intrusion and extrusion processes of a liquid into single pore are analyzed when the liquid is compressed or stretched so that the liquid phase is either stable or metastable relative to the vapor phase. Therefore, this model is also relevant to the stability of the superhydrophobic submerged substrates. In this study, the macroscopic classical capillary theory is adopted. Even within this simplified model, two simple geometries of truncated and inverted truncated cones lead to completely different free-energy landscapes. A simple criterion for the stability of the CB state based on Laplace pressure is shown not to be sufficient to understand the destruction and recovery of the CB state. The free-energy landscapes indicate that a gradual and an abrupt destruction of CB state is possible, which depends on the orientation of the conical pore and whether the liquid is compressed or stretched. The extensions of these theoretical results to more complex geometries are briefly discussed.
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Affiliation(s)
- Masao Iwamatsu
- Tokyo City University, Setagaya-ku, Tokyo 158-8557, Japan
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13
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Marchio S, Meloni S, Giacomello A, Casciola CM. Wetting and recovery of nano-patterned surfaces beyond the classical picture. NANOSCALE 2019; 11:21458-21470. [PMID: 31686077 DOI: 10.1039/c9nr05105h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Hydrophobic (nano)textured surfaces, also known as superhydrophobic surfaces, have a wide range of technological applications, including in the self-cleaning, anti-moisture, anti-icing, anti-fogging and friction/drag reduction fields, and many more. The accidental complete wetting of surface textures, which destroys superhydrophobicity, and the opposite process of recovery are two crucial processes that can prevent or enable the technological applications mentioned before. Understanding these processes is key to designing surfaces with tailored wetting and recovery properties. However, recent experiments have suggested that the currently available theories are insufficient for describing the observed phenomena. In this work we offer a dynamic picture of these processes beyond the state of the art showing that the key ingredient determining the experimental behavior is the inertia of the liquid in the wetting and dewetting processes, which is neglected in microscopic and macroscopic quasi-static theories inspired by the classical nucleation theory. The present findings are also important for other related phenomena, such as heterogeneous cavitation, where vapor/gas bubbles form at surface asperities, condensation, dynamics of the triple line, micelle formation, etc.
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Affiliation(s)
- Sara Marchio
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma Sapienza, Via Eudossiana 18, 00184 Roma, Italy.
| | - Simone Meloni
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma Sapienza, Via Eudossiana 18, 00184 Roma, Italy. and Dipartimento di Scienze Chimiche e Farmaceutiche (DipSCF), Universitá degli Studi di Ferrara (Unife), Via Luigi Borsari 46, I-44121, Ferrara, Italy.
| | - Alberto Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma Sapienza, Via Eudossiana 18, 00184 Roma, Italy.
| | - Carlo Massimo Casciola
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma Sapienza, Via Eudossiana 18, 00184 Roma, Italy.
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14
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Subramanian N, Qamar A, Alsaadi A, Gallo A, Ridwan MG, Lee JG, Pillai S, Arunachalam S, Anjum D, Sharipov F, Ghaffour N, Mishra H. Evaluating the potential of superhydrophobic nanoporous alumina membranes for direct contact membrane distillation. J Colloid Interface Sci 2019; 533:723-732. [DOI: 10.1016/j.jcis.2018.08.054] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 08/19/2018] [Accepted: 08/20/2018] [Indexed: 11/29/2022]
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15
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Domingues EM, Arunachalam S, Nauruzbayeva J, Mishra H. Biomimetic coating-free surfaces for long-term entrapment of air under wetting liquids. Nat Commun 2018; 9:3606. [PMID: 30190456 PMCID: PMC6127334 DOI: 10.1038/s41467-018-05895-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Accepted: 08/01/2018] [Indexed: 01/02/2023] Open
Abstract
Trapping air at the solid-liquid interface is a promising strategy for reducing frictional drag and desalting water, although it has thus far remained unachievable without perfluorinated coatings. Here, we report on biomimetic microtextures composed of doubly reentrant cavities (DRCs) and reentrant cavities (RCs) that can enable even intrinsically wetting materials to entrap air for long periods upon immersion in liquids. Using SiO2/Si wafers as the model system, we demonstrate that while the air entrapped in simple cylindrical cavities immersed in hexadecane is lost after 0.2 s, the air entrapped in the DRCs remained intact even after 27 days (~106 s). To understand the factors and mechanisms underlying this ten-million-fold enhancement, we compared the behaviors of DRCs, RCs and simple cavities of circular and non-circular shapes on immersion in liquids of low and high vapor pressures through high-speed imaging, confocal microscopy, and pressure cells. Those results might advance the development of coating-free liquid repellent surfaces.
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Affiliation(s)
- Eddy M Domingues
- King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science and Engineering (BESE) Division, Thuwal, 23955-6900, Saudi Arabia
| | - Sankara Arunachalam
- King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science and Engineering (BESE) Division, Thuwal, 23955-6900, Saudi Arabia
| | - Jamilya Nauruzbayeva
- King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science and Engineering (BESE) Division, Thuwal, 23955-6900, Saudi Arabia
| | - Himanshu Mishra
- King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science and Engineering (BESE) Division, Thuwal, 23955-6900, Saudi Arabia.
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Zhang Z, Chung S, Jang J. Molecular Dynamics Study on the Wetting Transition of a Hierarchical Groove. B KOREAN CHEM SOC 2018. [DOI: 10.1002/bkcs.11379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Zhengqing Zhang
- Department of Nanoenergy Engineering; Pusan National University; Busan 46241 Republic of Korea
| | - Sungwook Chung
- School of Chemical and Biomolecular Engineering; Pusan National University; Busan 46241 Republic of Korea
| | - Joonkyung Jang
- Department of Nanoenergy Engineering; Pusan National University; Busan 46241 Republic of Korea
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17
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Lisi E, Amabili M, Meloni S, Giacomello A, Casciola CM. Self-Recovery Superhydrophobic Surfaces: Modular Design. ACS NANO 2018; 12:359-367. [PMID: 29182848 DOI: 10.1021/acsnano.7b06438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Superhydrophobicity, the enhanced hydrophobicity of surfaces decorated with textures of suitable size, is associated with a layer of gas trapped within surface roughness. The reduced liquid/solid contact makes superhydrophobicity attractive for many technological applications. This gas layer, however, can break down with the liquid completely wetting the surface. Experiments have shown that the recovery of the "suspended" superhydrophobic state from the wet one is difficult. Self-recovery-the spontaneous restoring of the gas layer at ambient conditions-is one of the dreams of research in superhydrophobicity as it would allow to overcome the fragility of superhydrophobicity. In this work we have performed a theoretical investigation of the wetting and recovery processes on a set of surfaces characterized by textures of different dimensions and morphology in order to elucidate the optimal parameters for avoiding wetting and achieving self-recovery. Results show that texture size in the nanometer range is a necessary but not sufficient condition for self-recovery: the geometry plays a crucial role, nanopillars prevent self-recovery, while surfaces with square pores exhibit self-recovery even at large positive pressures. However, the optimal morphology for self-recovery, the square pore, is suboptimal for the functional properties of the surface, for example, high slippage. Our calculations show that these two properties are related to regions of the texture separated in space: self-recovery is controlled by the characteristics of the bottom surface, while wetting and slip are controlled by the cavity mouth. We thus propose a modular design strategy which combines self-recovery and good functional properties: Square pores surmounted by ridges achieve self-recovery even at 2 MPa and have a very small liquid/solid contact area. The macroscopic calculations, which allowed us to efficiently devise design criteria, have been validated by atomistic simulations, with the optimal texture showing self-recovery on atomic time scales, τ ∼ 2 ns.
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Affiliation(s)
- Emanuele Lisi
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , Rome, Italy
| | - Matteo Amabili
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , Rome, Italy
| | - Simone Meloni
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , Rome, Italy
| | - Alberto Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , Rome, Italy
| | - Carlo Massimo Casciola
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , Rome, Italy
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18
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Amabili M, Meloni S, Giacomello A, Casciola CM. Activated Wetting of Nanostructured Surfaces: Reaction Coordinates, Finite Size Effects, and Simulation Pitfalls. J Phys Chem B 2017; 122:200-212. [PMID: 29200302 DOI: 10.1021/acs.jpcb.7b07429] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A liquid in contact with a textured surface can be found in two states, Wenzel and Cassie. In the Wenzel state the liquid completely wets the corrugations while in the Cassie state the liquid is suspended over the corrugations with air or vapor trapped below. The superhydrophobic properties of the Cassie state are exploited for self-cleaning, drag reduction, drug delivery, etc., while in the Wenzel state most of these properties are lost; it is therefore of great fundamental and technological interest to investigate the kinetics and mechanism of the Cassie-Wenzel transition. Computationally, the Cassie-Wenzel transition is often investigated using enhanced sampling ("rare events") techniques based on the use of collective variables (CVs). The choice of the CVs is a crucial task because it affects the free-energy profile, the estimation of the free-energy barriers, and the evaluation of the mechanism of the process. Here we investigate possible simulation artifacts introduced by common CVs adopted for the study of the Cassie-Wenzel transition: the average particle density in the corrugation of a textured surface and the coarse-grained density field at various levels of coarse graining. We also investigate possible additional artifacts associated with finite size effects. We focus on a pillared surface, a system often used in technological applications. We show that the use of a highly coarse-grained density (a single CV) of the fluid in the interpillar region brings to severe artifacts: errors of hundreds of kBT in the difference of free energy between the Cassie and Wenzel states, of tens of kBT in the estimate of the free-energy barriers, and erroneous wetting mechanisms. A proper description of the wetting mechanism and its energetics apparently requires a fine discretization of the density field. Concerning the finite-size effects, we have found that the typical systems employed in simulations of the Cassie-Wenzel transition, containing a single pillar within periodic boundary conditions, prevent the complete break of translational symmetry of the liquid-vapor meniscus during the process. Capturing this break of symmetry is crucial for describing the transition state along the wetting process and the early stage of the opposite process, the Wenzel-Cassie transition.
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Affiliation(s)
- M Amabili
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , 00184 Rome, Italy
| | - S Meloni
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , 00184 Rome, Italy
| | - A Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , 00184 Rome, Italy
| | - C M Casciola
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma "La Sapienza" , 00184 Rome, Italy
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19
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Pan Z, Cheng F, Zhao B. Bio-Inspired Polymeric Structures with Special Wettability and Their Applications: An Overview. Polymers (Basel) 2017; 9:E725. [PMID: 30966026 PMCID: PMC6418807 DOI: 10.3390/polym9120725] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 12/08/2017] [Accepted: 12/14/2017] [Indexed: 12/15/2022] Open
Abstract
It is not unusual for humans to be inspired by natural phenomena to develop new advanced materials; such materials are called bio-inspired materials. Interest in bio-inspired polymeric superhydrophilic, superhydrophobic, and superoleophobic materials has substantially increased over the last few decades, as has improvement in the related technologies. This review reports the latest developments in bio-inspired polymeric structures with desired wettability that have occurred by mimicking the structures of lotus leaf, rose petals, and the wings and shells of various creatures. The intrinsic role of surface chemistry and structure on delivering superhydrophilicity, superhydrophobicity, and superoleophobicity has been extensively explored. Typical polymers, commonly used structures, and techniques involved in developing bio-inspired surfaces with desired wettability are discussed. Additionally, the latest applications of bio-inspired structures with desired wettability in human activities are also introduced.
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Affiliation(s)
- Zihe Pan
- Institute of Resources and Environmental Engineering, Shanxi University, 92 Wucheng Road, Xiaodian District, Taiyuan 030006, Shanxi, China.
- Shanxi Collaborative Innovation Center of High Value-Added Utilization of Coal-Related Wastes, Taiyuan 030006, Shanxi, China.
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
| | - Fangqin Cheng
- Institute of Resources and Environmental Engineering, Shanxi University, 92 Wucheng Road, Xiaodian District, Taiyuan 030006, Shanxi, China.
- Shanxi Collaborative Innovation Center of High Value-Added Utilization of Coal-Related Wastes, Taiyuan 030006, Shanxi, China.
| | - Boxin Zhao
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
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20
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Simovich T, Ritchie C, Belev G, Cooper DML, Lamb RN. Superhydrophobicity from the Inside. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13990-13995. [PMID: 29064712 DOI: 10.1021/acs.langmuir.7b01350] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The nature of trapped air on submersed ultra-water-repellent interfaces has been investigated. These gaseous layers (plastrons) can last from hours to, in some examples such as the Salvinia molesta fern, months. The interface of submerged superhydrophobic surfaces with carefully controlled micropatterned surface roughness has been probed using synchrotron-based high-resolution X-ray phase tomography. This technique looks in situ, through the aqueous/gas interface in three dimensions. Long-term plastron stability appears to correlate with the appearance of scattered microdroplets <20 μm in diameter that are sandwiched within the 30 μm thick gaseous interfacial layer. These microdroplets are centered on defects or damaged sections within the substrate surface approximately 20-50 μm apart. Such irregularities represent heterogeneous micro/nano-hierarchical structures with varying surface structures and chemistry. The stability of microdroplets is governed by a combination of electrostatic repulsion, contact angle limitations, and a saturated vapor pressure, the latter of which reduces the rate of diffusion of gas out of the air layer, thus increasing underwater longevity. Homogenous surfaces exhibiting purely nano- or micro-regularity do not support such microdroplets, and, as a consequence, plastrons can disappear in <20 h compared with >160 h for surfaces with scattered microdroplets. Such behavior may be a requirement for long-term nonwetting in any system.
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Affiliation(s)
- Tomer Simovich
- School of Chemistry, University of Melbourne , Parkville 3010, Victoria, Australia
| | - Cameron Ritchie
- School of Chemistry, University of Melbourne , Parkville 3010, Victoria, Australia
- Bio21 Institute, University of Melbourne , Parkville 3010, Victoria, Australia
| | - George Belev
- Canadian Light Source (CLS) , Saskatoon, Saskatchewan S7N 2V3, Canada
| | - David M L Cooper
- Department of Anatomy and Cell Biology, University of Saskatchewan , Saskatoon, Saskatchewan S7N 2V3, Canada
| | - Robert N Lamb
- School of Chemistry, University of Melbourne , Parkville 3010, Victoria, Australia
- Canadian Light Source (CLS) , Saskatoon, Saskatchewan S7N 2V3, Canada
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21
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Peng Y, Jin X, Zheng Y, Han D, Liu K, Jiang L. Direct Imaging of Superwetting Behavior on Solid-Liquid-Vapor Triphase Interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 28869679 DOI: 10.1002/adma.201703009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/17/2017] [Indexed: 05/11/2023]
Abstract
A solid-liquid-vapor interface dominated by a three-phase contact line usually serves as an active area for interfacial reactions and provides a vital clue to surface behavior. Recently, direct imaging of the triphase interface of superwetting interfaces on the microscale/nanoscale has attracted broad scientific attention for both theoretical research and practical applications, and has gradually become an efficient and intuitive approach to explore the wetting behaviors of various multiphase interfaces. Here, recent progress on characterizing the solid-liquid-vapor triphase interface on the microscale/nanoscale with diverse types of imaging apparatus is summarized. Moreover, the accurate, visible, and quantitative information that can be obtained shows the real interfacial morphology of the wetting behaviors of multiphase interfaces. On the basis of fundamental research, technical innovations in imaging and complicated multiphase interfaces of the superwetting surface are also briefly presented.
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Affiliation(s)
- Yun Peng
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Xu Jin
- Research Institute of Petroleum, Exploration and Development, Petro China, Beijing, 100191, P. R. China
| | - Yongmei Zheng
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Dong Han
- National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Kesong Liu
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Lei Jiang
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing, 100191, P. R. China
- Laboratory of Bio-inspired Smart Interface Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China
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22
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Domingues EM, Arunachalam S, Mishra H. Doubly Reentrant Cavities Prevent Catastrophic Wetting Transitions on Intrinsically Wetting Surfaces. ACS APPLIED MATERIALS & INTERFACES 2017; 9:21532-21538. [PMID: 28580784 DOI: 10.1021/acsami.7b03526] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Omniphobic surfaces, that is, which repel all known liquids, have proven of value in applications ranging from membrane distillation to underwater drag reduction. A limitation of currently employed omniphobic surfaces is that they rely on perfluorinated coatings, increasing cost and environmental impact and preventing applications in harsh environments. Thus, there is a keen interest in rendering conventional materials, such as plastics, omniphobic by micro/nanotexturing rather than via chemical makeup, with notable success having been achieved for silica surfaces with doubly reentrant micropillars. However, we found a critical limitation of microtextures comprising pillars that they undergo catastrophic wetting transitions (apparent contact angles, θr → 0° from θr > 90°) in the presence of localized physical damages/defects or on immersion in wetting liquids. In response, a doubly reentrant cavity microtexture is introduced, which can prevent catastrophic wetting transitions in the presence of localized structural damage/defects or on immersion in wetting liquids. Remarkably, our silica surfaces with doubly reentrant cavities could exhibit apparent contact angles, θr ≈ 135° for mineral oil, where the intrinsic contact angle, θo ≈ 20°. Further, when immersed in mineral oil or water, doubly reentrant microtextures in silica (θo ≈ 40° for water) were not penetrated even after several days of investigation. Thus, microtextures comprising doubly reentrant cavities might enable applications of conventional materials without chemical modifications, especially in scenarios that are prone to localized damages or immersion in wetting liquids, for example, hydrodynamic drag reduction and membrane distillation.
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Affiliation(s)
- Eddy M Domingues
- Water Desalination and Reuse Center (WDRC) and Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia
| | - Sankara Arunachalam
- Water Desalination and Reuse Center (WDRC) and Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia
| | - Himanshu Mishra
- Water Desalination and Reuse Center (WDRC) and Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia
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23
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He Y, Zhou Q, Wang S, Yang R, Jiang C, Yuan W. In Situ Observation of Dynamic Wetting Transition in Re-Entrant Microstructures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3949-3953. [PMID: 28394611 DOI: 10.1021/acs.langmuir.7b00256] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Re-entrant microstructures exhibit excellent wetting stability under different pressure levels, but the underlying mechanism determined by wetting transition behavior at the microscale level remains unclear. We propose the "wetting chip" method for in situ assessment of the dynamic behavior of wetting transition in re-entrant microstructures. High sag and transverse depinning were observed in re-entrant microstructures. Analysis indicated that high sag and transverse depinning mainly influenced the stability of the structures. The threshold pressure and longevity of wetting transition were predicted and experimentally verified. The design criteria of wetting stability, including small geometry design, hydrophobic material selection, and sidewall condition, were also presented. The proposed method and model can be applied to different shapes and geometry microstructures to elucidate wetting stability.
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Affiliation(s)
- Yang He
- Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China
| | - Qingqing Zhou
- Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China
| | - Shengkun Wang
- Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China
| | - Ruyuan Yang
- Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China
| | - Chengyu Jiang
- Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China
| | - Weizheng Yuan
- Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China
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24
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Panter JR, Kusumaatmaja H. The impact of surface geometry, cavitation, and condensation on wetting transitions: posts and reentrant structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:084001. [PMID: 28092626 DOI: 10.1088/1361-648x/aa5380] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The fundamental impacts of surface geometry on the stability of wetting states, and the transitions between them are elucidated for square posts and reentrant structures in three dimensions. We identify three principal outcomes of particular importance for future surface design of liquid-repellent surfaces. Firstly, we demonstrate and quantify how capillary condensation and vapour cavitation affect wetting state stabilities. At high contact angles, cavitation is enhanced about wide, closely-spaced square posts, leading to the existence of suspended states without an associated collapsed state. At low contact angles, narrow reentrant pillars suppress condensation and enable the suspension of even highly wetting liquids. Secondly, two distinct collapse mechanisms are observed for 3D reentrant geometries, base contact and pillar contact, which are operative at different pillar heights. As well as morphological differences in the interface of the penetrating liquid, each mechanism is affected differently by changes in the contact angle with the solid. Finally, for highly-wetting liquids, condensates are shown to critically modify the transition pathways in both the base contact and pillar contact modes.
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Affiliation(s)
- J R Panter
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
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25
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Wu H, Yang Z, Cao B, Zhang Z, Zhu K, Wu B, Jiang S, Chai G. Wetting and Dewetting Transitions on Submerged Superhydrophobic Surfaces with Hierarchical Structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:407-416. [PMID: 27989127 DOI: 10.1021/acs.langmuir.6b03752] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The wetting transition on submersed superhydrophobic surfaces with hierarchical structures and the influence of trapped air on superhydrophobic stability are predicted based on the thermodynamics and mechanical analyses. The dewetting transition on the hierarchically structured surfaces is investigated, and two necessary thermodynamic conditions and a mechanical balance condition for dewetting transition are proposed. The corresponding thermodynamic phase diagram of reversible transition and the critical reversed pressure well explain the experimental results reported previously. Our theory provides a useful guideline for precise controlling of breaking down and recovering of superhydrophobicity by designing superhydrophobic surfaces with hierarchical structures under water.
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Affiliation(s)
- Huaping Wu
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
- Jiangsu Key Laboratory of Engineering Mechanics, Southeast University , Nanjing 210096, China
| | - Zhe Yang
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
| | - Binbin Cao
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
| | - Zheng Zhang
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
| | - Kai Zhu
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
| | - Bingbing Wu
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
| | - Shaofei Jiang
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
| | - Guozhong Chai
- Key Laboratory of E&M, Zhejiang University of Technology , Ministry of Education & Zhejiang Province, Hangzhou 310014, China
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26
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27
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Meloni S, Giacomello A, Casciola CM. Focus Article: Theoretical aspects of vapor/gas nucleation at structured surfaces. J Chem Phys 2016; 145:211802. [DOI: 10.1063/1.4964395] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Simone Meloni
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, via Eudossiana 18, 00184 Roma, Italy
| | - Alberto Giacomello
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, via Eudossiana 18, 00184 Roma, Italy
| | - Carlo Massimo Casciola
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, via Eudossiana 18, 00184 Roma, Italy
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28
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Xiang Y, Xue Y, Lv P, Li D, Duan H. Influence of fluid flow on the stability and wetting transition of submerged superhydrophobic surfaces. SOFT MATTER 2016; 12:4241-4246. [PMID: 27071538 DOI: 10.1039/c6sm00302h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Superhydrophobic surfaces have attracted great attention for drag reduction application. However, these surfaces are subject to instabilities, especially under fluid flow. In this work, we in situ examine the stability and wetting transition of underwater superhydrophobicity under laminar flow conditions by confocal microscopy. The absolute liquid pressure in the flow channel is regulated to acquire the pinned Cassie-Baxter and depinned metastable states. The subsequent dynamic evolution of the meniscus morphology in the two states under shear flow is monitored. It is revealed that fluid flow does not affect the pressure-mediated equilibrium states but accelerates the air exchange between entrapped air cavities and bulk water. A diffusion-based model with varying effective diffusion lengths is used to interpret the experimental data, which show a good agreement. The Sherwood number representing the convection-enhanced mass transfer coefficient is extracted from the data, and is found to follow a classic 1/3-power-law relation with the Reynolds number as has been discovered in channel flows with diffusive boundary conditions. The current work paves the way for designing durable superhydrophobic surfaces under flow conditions.
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Affiliation(s)
- Yaolei Xiang
- State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, People's Republic of China.
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29
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Schneider L, Laustsen M, Mandsberg N, Taboryski R. The Influence of Structure Heights and Opening Angles of Micro- and Nanocones on the Macroscopic Surface Wetting Properties. Sci Rep 2016; 6:21400. [PMID: 26892169 PMCID: PMC4759530 DOI: 10.1038/srep21400] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 01/22/2016] [Indexed: 11/09/2022] Open
Abstract
We discuss the influence of surface structure, namely the height and opening angles of nano- and microcones on the surface wettability. We show experimental evidence that the opening angle of the cones is the critical parameter on sample superhydrophobicity, namely static contact angles and roll-off angles. The textured surfaces are fabricated on silicon wafers by using a simple one-step method of reactive ion etching at different processing time and gas flow rates. By using hydrophobic coating or hydrophilic surface treatment, we are able to switch the surface wettability from superhydrophilic to superhydrophobic without altering surface structures. In addition, we show examples of polymer replicas (polypropylene and poly(methyl methacrylate) with different wettability, fabricated by injection moulding using templates of the silicon cone-structures.
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Affiliation(s)
- Ling Schneider
- Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Milan Laustsen
- Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Nikolaj Mandsberg
- Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Rafael Taboryski
- Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
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30
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Hensel R, Neinhuis C, Werner C. The springtail cuticle as a blueprint for omniphobic surfaces. Chem Soc Rev 2015; 45:323-41. [PMID: 26239626 DOI: 10.1039/c5cs00438a] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Omniphobic surfaces found in nature have great potential for enabling novel and emerging products and technologies to facilitate the daily life of human societies. One example is the water and even oil-repellent cuticle of springtails (Collembola). The wingless arthropods evolved a highly textured, hierarchically arranged surface pattern that affords mechanical robustness and wetting resistance even at elevated hydrostatic pressures. Springtail cuticle-derived surfaces therefore promise to overcome limitations of lotus-inspired surfaces (low durability, insufficient repellence of low surface tension liquids). In this review, we report on the liquid-repellent natural surfaces of arthropods living in aqueous or temporarily flooded habitats including water-walking insects or water spiders. In particular, we focus on springtails presenting an overview on the cuticular morphology and chemistry and their biological relevance. Based on the obtained liquid repellence of a variety of liquids with remarkable efficiency, the review provides general design criteria for robust omniphobic surfaces. In particular, the resistance against complete wetting and the mechanical stability strongly both depend on the topographical features of the nano- and micropatterned surface. The current understanding of the underlying principles and approaches to their technological implementation are summarized and discussed.
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Affiliation(s)
- René Hensel
- INM - Leibniz Institute for New Materials, 66123 Saarbrücken, Germany
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