1
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Vieira A, Jokinen V, Lepikko S, Ras RHA, Zhou Q. Through-Drop Imaging of Liquid-Solid Interfaces: From Contact Angle Variations Along the Droplet Perimeter to Mapping of Contact Angles Across a Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:9059-9067. [PMID: 38621291 PMCID: PMC11072716 DOI: 10.1021/acs.langmuir.4c00414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 03/28/2024] [Accepted: 03/28/2024] [Indexed: 04/17/2024]
Abstract
When a droplet interacts with a water-repellent surface, its triple-phase contact line typically exhibits varying contact angles, which can vary from point-to-point across the surface. Consequently, measuring the contact angles along the contact line would provide a better representation of the wetting properties of the surface than a single average contact angle. However, an effective method for estimating the local contact angle along the contact line on opaque hydrophobic surfaces is currently lacking. Here we present a method that combines through-drop imaging of the wetting interface during a sliding experiment with Finite Element Modeling of the droplet to estimate contact angle values along the contact line. Using this method, the mean advancing and receding contact angles were measured on four types of hydrophobic samples with contact angles between 99 and 178.9°. The method was further used to produce detailed advancing and receding contact angle maps of surfaces with wetting patterns with an unprecedented resolution of 3 μm.
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Affiliation(s)
- Arthur Vieira
- Department
of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, Maarintie 8, 02150 Espoo, Finland
| | - Ville Jokinen
- Department
of Chemistry and Materials Science, School
of Chemical Engineering, Aalto University, Tietotie 3, 02150 Espoo, Finland
| | - Sakari Lepikko
- Department
of Applied Physics, Aalto University, 02150 Espoo, Finland
- Centre
of Excellence in Life-Inspired Hybrid Materials (LIBER), Aalto University, 02150 Espoo, Finland
| | - Robin H. A. Ras
- Department
of Applied Physics, Aalto University, 02150 Espoo, Finland
- Centre
of Excellence in Life-Inspired Hybrid Materials (LIBER), Aalto University, 02150 Espoo, Finland
| | - Quan Zhou
- Department
of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, Maarintie 8, 02150 Espoo, Finland
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2
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Kumar P, Mulvaney P, Harvie DJE. Energy dissipation during homogeneous wetting of surfaces with randomly and periodically distributed cylindrical pillars. J Colloid Interface Sci 2024; 659:105-118. [PMID: 38159487 DOI: 10.1016/j.jcis.2023.12.134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 12/12/2023] [Accepted: 12/20/2023] [Indexed: 01/03/2024]
Abstract
HYPOTHESIS Understanding contact angle hysteresis on rough surfaces is important as most industrially relevant and naturally occurring surfaces possess some form of random or structured roughness. We hypothesise that hysteresis can be described by the dilute defect model of Joanny & de Gennes [1] and that the energy dissipation occurring during the stick-slip motion of the contact line is key to developing a predictive equation for hysteresis. EXPERIMENTS We measured hysteresis on surfaces with randomly distributed and periodically arranged microscopic cylindrical pillars for a variety of different liquids in air. The inherent (flat surface) contact angles tested range from lyophilic (θe=33.8°) to lyophobic (θe=112.0°). FINDINGS A methodology for averaging the measured advancing and receding contact angles on random surfaces is presented. Based on these results correlations for roughness-induced energy dissipation are derived, and an equation for predicting the advancing and receding contact angles during homogeneous (Wenzel) wetting on random surfaces is presented. Equations that predict the onset of the alternate wetting conditions of hemiwicking, split-advancing, split-receding and heterogeneous (Cassie) wetting are also derived, thus defining the range of validity for the homogeneous wetting equation. A 'cluster' concept is proposed to explain the measurably higher hysteresis exhibited by structured surfaces compared to random surfaces.
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Affiliation(s)
- Pawan Kumar
- Multiphysics Fluid Dynamics Group, Department of Chemical Engineering, University of Melbourne, Parkville, Melbourne, 3010, Victoria, Australia
| | - Paul Mulvaney
- ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Melbourne, Parkville, Melbourne, 3010, Victoria, Australia
| | - Dalton J E Harvie
- Multiphysics Fluid Dynamics Group, Department of Chemical Engineering, University of Melbourne, Parkville, Melbourne, 3010, Victoria, Australia.
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3
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Eriksson M, Claesson PM, Järn M, Wallqvist V, Tuominen M, Kappl M, Teisala H, Vollmer D, Schoelkopf J, Gane PA, Mäkelä JM, Swerin A. Effects of Gas Layer Thickness on Capillary Interactions at Superhydrophobic Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:4801-4810. [PMID: 38386540 PMCID: PMC10919075 DOI: 10.1021/acs.langmuir.3c03709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 02/12/2024] [Accepted: 02/13/2024] [Indexed: 02/24/2024]
Abstract
Strongly attractive forces act between superhydrophobic surfaces across water due to the formation of a bridging gas capillary. Upon separation, the attraction can range up to tens of micrometers as the gas capillary grows, while gas molecules accumulate in the capillary. We argue that most of these molecules come from the pre-existing gaseous layer found at and within the superhydrophobic coating. In this study, we investigate how the capillary size and the resulting capillary forces are affected by the thickness of the gaseous layer. To this end, we prepared superhydrophobic coatings with different thicknesses by utilizing different numbers of coating cycles of a liquid flame spraying technique. Laser scanning confocal microscopy confirmed an increase in gas layer thickness with an increasing number of coating cycles. Force measurements between such coatings and a hydrophobic colloidal probe revealed attractive forces caused by bridging gas capillaries, and both the capillary size and the range of attraction increased with increasing thickness of the pre-existing gas layer. Hence, our data suggest that the amount of available gas at and in the superhydrophobic coating determines the force range and capillary growth.
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Affiliation(s)
- Mimmi Eriksson
- Materials
and Surface Design, RISE Research Institutes
of Sweden, SE-11486 Stockholm, Sweden
- Department
of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
- CR
Colloidal Resource AB, Naturvetarvägen 14, SE-22362 Lund, Sweden
| | - Per M. Claesson
- Department
of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Mikael Järn
- Materials
and Surface Design, RISE Research Institutes
of Sweden, SE-11486 Stockholm, Sweden
| | - Viveca Wallqvist
- Materials
and Surface Design, RISE Research Institutes
of Sweden, SE-11486 Stockholm, Sweden
| | - Mikko Tuominen
- Materials
and Surface Design, RISE Research Institutes
of Sweden, SE-11486 Stockholm, Sweden
- Nordtreat
Oy, Mestarintie 11, FI-01730 Vantaa, Finland
| | - Michael Kappl
- Department
of Physics at Interfaces, Max Planck Institute
for Polymer Research, D-55128 Mainz, Germany
| | - Hannu Teisala
- Department
of Physics at Interfaces, Max Planck Institute
for Polymer Research, D-55128 Mainz, Germany
- Amcor
Flexibles Valkeakoski Oy, Niementie 161, P.O. Box 70, 37601 Valkeakoski, Finland
| | - Doris Vollmer
- Department
of Physics at Interfaces, Max Planck Institute
for Polymer Research, D-55128 Mainz, Germany
| | | | - Patrick A.C. Gane
- School
of Chemical Engineering, Department of Bioproducts and Biosystems, Aalto University, FI-00076 Aalto, Finland
- Faculty of
Technology and Metallurgy, University of
Belgrade, Karnegijeva
4, Belgrade 11000, Serbia
| | - Jyrki M. Mäkelä
- Physics
Unit, Aerosol Physics Laboratory, Tampere
University, Tampere FI-33014, Finland
| | - Agne Swerin
- Department
of Chemistry, Division of Surface and Corrosion Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
- Department
of Engineering and Chemical Sciences, Karlstad
University, SE-651 88 Karlstad, Sweden
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4
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Rasitha TP, Krishna NG, Anandkumar B, Vanithakumari SC, Philip J. A comprehensive review on anticorrosive/antifouling superhydrophobic coatings: Fabrication, assessment, applications, challenges and future perspectives. Adv Colloid Interface Sci 2024; 324:103090. [PMID: 38290251 DOI: 10.1016/j.cis.2024.103090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 01/16/2024] [Accepted: 01/16/2024] [Indexed: 02/01/2024]
Abstract
Superhydrophobicity (SHP) is an incredible phenomenon of extreme water repellency of surfaces ubiquitous in nature (E.g. lotus leaves, butterfly wings, taro leaves, mosquito eyes, water-strider legs, etc). Historically, surface exhibiting water contact angle (WCA) > 150° and contact angle hysteresis <10° is considered as SHP. The SHP surfaces garnered considerable attention in recent years due to their applications in anti-corrosion, anti-fouling, self-cleaning, oil-water separation, viscous drag reduction, anti-icing, etc. As corrosion and marine biofouling are global problems, there has been focused efforts in combating these issues using innovative environmentally friendly coatings designs taking cues from natural SHP surfaces. Over the last two decades, though significant progress has been made on the fabrication of various SHP surfaces, the practical adaptation of these surfaces for various applications is hampered, mainly because of the high cost, non-scalability, lack of simplicity, non-adaptability for a wide range of substrates, poor mechanical robustness and chemical inertness. Despite the extensive research, the exact mechanism of corrosion/anti-fouling of such coatings also remains elusive. The current focus of research in recent years has been on the development of facile, eco-friendly, cost-effective, mechanically robust chemically inert, and scalable methods to prepare durable SHP coating on a variety of surfaces. Although there are some general reviews on SHP surfaces, there is no comprehensive review focusing on SHP on metallic and alloy surfaces with corrosion-resistant and antifouling properties. This review is aimed at filling this gap. This review provides a pedagogical description with the necessary background, key concepts, genesis, classical models of superhydrophobicity, rational design of SHP, coatings characterization, testing approaches, mechanisms, and novel fabrication approaches currently being explored for anticorrosion and antifouling, both from a fundamental and practical perspective. The review also provides a summary of important experimental studies with key findings, and detailed descriptions of the evaluation of surface morphologies, chemical properties, mechanical, chemical, corrosion, and antifouling properties. The recent developments in the fabrication of SHP -Cr-Mo steel, Ti, and Al are presented, along with the latest understanding of the mechanism of anticorrosion and antifouling properties of the coating also discussed. In addition, different promising applications of SHP surfaces in diverse disciplines are discussed. The last part of the review highlights the challenges and future directions. The review is an ideal material for researchers practicing in the field of coatings and also serves as an excellent reference for freshers who intend to begin research on this topic.
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Affiliation(s)
- T P Rasitha
- Corrosion Science and Technology Division, Materials Characterization Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India
| | - Nanda Gopala Krishna
- Corrosion Science and Technology Division, Materials Characterization Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India
| | - B Anandkumar
- Corrosion Science and Technology Division, Materials Characterization Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India; Homi Bhabha National Institute, Kalpakkam 603102, India
| | - S C Vanithakumari
- Corrosion Science and Technology Division, Materials Characterization Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India; Homi Bhabha National Institute, Kalpakkam 603102, India
| | - John Philip
- Corrosion Science and Technology Division, Materials Characterization Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India; Homi Bhabha National Institute, Kalpakkam 603102, India.
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5
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Shamim JA, Takahashi Y, Goswami A, Shaukat N, Hsu WL, Choi J, Daiguji H. Suppression of wetting transition on evaporative fakir droplets by using slippery superhydrophobic surfaces with low depinning force. Sci Rep 2023; 13:2368. [PMID: 36759577 PMCID: PMC9911698 DOI: 10.1038/s41598-023-29163-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 01/31/2023] [Indexed: 02/11/2023] Open
Abstract
This study experimentally investigated the evaporation and wetting transition behavior of fakir droplets on five different microstructured surfaces. Diamond-like carbon was introduced as the substrate, and the influence of varying the width, height, and pitch of the micropillars was assessed. The experimental results showed that the interfacial properties of the surfaces change the evaporation behavior and the starting point of the wetting transition. An important result of this study is the demonstration of a slippery superhydrophobic surface with low depinning force that suppresses the transition from the Cassie-Baxter state to the Wenzel state for microdroplets less than 0.37 mm in diameter, without employing large pillar height or multiscale roughness. By selecting an appropriate pillar pitch and employing tapered micropillars with small pillar widths, the solid-liquid contact at the three-phase contact line was reduced and low depinning forces were obtained. The underlying mechanism by which slippery superhydrophobic surfaces suppress wetting transitions is also discussed. The accuracy of the theoretical models for predicting the critical transition parameters was assessed, and a numerical model was developed in the surface evolver to compute the penetration of the droplet bottom meniscus within the micropillars.
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Affiliation(s)
- Jubair A. Shamim
- grid.26999.3d0000 0001 2151 536XDepartment of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656 Japan
| | - Yukinari Takahashi
- grid.26999.3d0000 0001 2151 536XDepartment of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656 Japan
| | - Anjan Goswami
- grid.7445.20000 0001 2113 8111Department of Mechanical Engineering, Imperial College London, London, SW7 2AZ UK
| | - Nadeem Shaukat
- grid.420112.40000 0004 0607 7017Center for Mathematical Sciences, Pakistan Institute of Engineering and Applied Sciences, Nilore, 45650 Islamabad Pakistan
| | - Wei-Lun Hsu
- grid.26999.3d0000 0001 2151 536XDepartment of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656 Japan
| | - Junho Choi
- grid.26999.3d0000 0001 2151 536XDepartment of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656 Japan
| | - Hirofumi Daiguji
- Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656, Japan.
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6
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Varol HS, Seeger S. Droplet Size-Assisted Polysiloxane Architecting. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:377-388. [PMID: 36527409 DOI: 10.1021/acs.langmuir.2c02607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
(Super)antiwetting shielding around engineering materials and protecting them against harsh environmental conditions have been achieved via growing various geometry polysiloxane (or silicone) patterns around them by using a droplet-assisted growth method, where the polymerization takes place inside of the water droplets acting as reaction vessels. The size and distribution of these reaction vessels are the main factors in making different geometry silicone patterns; however, very little is known about the fate of these droplets throughout the polymerization. Here, we propose keeping the relative humidity (% RH) inside the reactor stable throughout the polymerization as a new coating parameter to force the size of the reaction vessel water droplets to be the same for building simply shaped silicone rods with controlled geometry and distribution. In this manner, we grew simple geometry cylindric microrods on surfaces and could tune their length, diameter, inter-rod spacing, and thus the (super)hydrophobicity. Here, we also demonstrate that with changes in the amplitude and stability of the % RH, it is possible to fabricate different (super)hydrophobic nanograsses, conical silicone microrods, and isotropic silicone nanofilaments. The proposed new way of tuning initial and in situ reaction vessel droplet size can be used as a single factor to formulate different geometry silicone patterns with tunable dimensions, leading to different roughness and hydrophobicity. To a certain extent, the droplet size-assisted silicone shaping in this work provides a new way to control the length, diameter, morphology, inter-rod spacing, and thus the (super)hydrophobicity of the silicone patterns, especially those in the shape of simple cylindrical microrods. This control over silicone architecting will help to prepare new (super)hydrophobic coatings with more controlled morphology and thus wettability; on the contrary, it will support surface scientists modeling the connection between surface geometry and (super)antiwetting of such irregular pillared surfaces that remain elusive.
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Affiliation(s)
- H Samet Varol
- Department of Chemistry, Universität Zürich, ZürichCH 8057, Switzerland
- Ernst-Berl Institut für Technische und Makromolekulare Chemie, Technische Universität Darmstadt, DarmstadtD-64287, Germany
| | - Stefan Seeger
- Department of Chemistry, Universität Zürich, ZürichCH 8057, Switzerland
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7
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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 (BASEL, SWITZERLAND) 2022; 15:4747. [PMID: 35888211 PMCID: PMC9317979 DOI: 10.3390/ma15144747] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [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.)
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8
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Dent F, Harbottle D, Warren NJ, Khodaparast S. Temporally Arrested Breath Figure. ACS APPLIED MATERIALS & INTERFACES 2022; 14:27435-27443. [PMID: 35658418 PMCID: PMC9204694 DOI: 10.1021/acsami.2c05635] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
Since its original conception as a tool for manufacturing porous materials, the breath figure method (BF) and its variations have been frequently used for the fabrication of numerous micro- and nanopatterned functional surfaces. In classical BF, reliable design of the final pattern has been hindered by the dual role of solvent evaporation to initiate/control the dropwise condensation and induce polymerization, alongside the complex effects of local humidity and temperature influence. Herein, we provide a deterministic method for reliable control of BF pore diameters over a wide range of length scales and environmental conditions. To this end, we employ an adapted methodology that decouples cooling from polymerization by using a combination of initiative cooling and quasi-instantaneous UV curing to deliberately arrest the desired BF patterns in time. Through in situ real-time optical microscopy analysis of the condensation kinetics, we demonstrate that an analytically predictable self-similar regime is the predominant arrangement from early to late times O(10-100 s), when high-density condensation nucleation is initially achieved on the polymer films. In this regime, the temporal growth of condensation droplets follows a unified power law of D ∝ t. Identification and quantitative characterization of the scale-invariant self-similar BF regime allow fabrication of programmed pore size, ranging from hundreds of nanometers to tens of micrometers, at high surface coverage of around 40%. Finally, we show that temporal arresting of BF patterns can be further extended for selective surface patterning and/or pore size modulation by spatially masking the UV curing illumination source. Our findings bridge the gap between fundamental knowledge of dropwise condensation and applied breath figure patterning techniques, thus enabling mechanistic design and fabrication of porous materials and interfaces.
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Affiliation(s)
- Francis
J. Dent
- School
of Mechanical Engineering, University of
Leeds, LS2 9JT Leeds, U.K.
| | - David Harbottle
- School
of Chemical and Process Engineering, University
of Leeds, LS2 9JT Leeds, U.K.
| | - Nicholas J. Warren
- School
of Chemical and Process Engineering, University
of Leeds, LS2 9JT Leeds, U.K.
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9
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Varol HS, Seeger S. Fluorescent Staining of Silicone Micro- and Nanopatterns for Their Optical Imaging. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:231-243. [PMID: 34932361 DOI: 10.1021/acs.langmuir.1c02436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Performance of engineered surfaces can be enhanced by making them hydrophobic or superhydrophobic via coating them with low-surface-energy micro- and nanopatterns. However, the wetting phenomena of particularly irregular shape and spacing (super)hydrophobic patterns such as polysiloxane coatings are not yet fully understood from a microscopic perspective. Here, we show a new method to collect 3D confocal images from irregular polysiloxane micro- and nanorods from a single rod resolution to discuss their wetting response over long liquid/solid interaction times and quantify the length and diameter of these rods. To collect such 3D confocal images, fluorescent dye containing water droplets were left on our superhydrophobic and hydrophobic polysiloxane coated surfaces. Then their liquid/solid interfaces were imaged at different staining scenarios: (i) using different fluorescent dyes, (ii) when the droplets were in contact with surfaces, or (iii) after the droplets were taken away from the surface at the end of staining. Using such staining strategies, we could resolve the micro- and nanorods from root to top and determine their length and diameter, which were then found to be in good agreement with those obtained from their electron microscopy images. 3D confocal images in this paper, for the first time, present the long-time existence of more than one wetting state under the same droplet in contact with surfaces, as well as external and internal three-phase contact lines shifting and pinning. In the end, these findings were used to explain the time-dependent wetting kinetics of our surfaces. We believe that the proposed imaging strategy here will, in the future, be used to study many other irregular patterned (super)antiwetting surfaces to describe their wetting theory, which is today impossible due to the complicated surface geometry of these irregular patterns.
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Affiliation(s)
- H Samet Varol
- Department of Chemistry, Universität Zürich, Zürich, CH 8057, Switzerland
- Ernst-Berl Institut für Technische und Makromolekulare Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str. 12, Darmstadt, D-64287, Germany
| | - Stefan Seeger
- Department of Chemistry, Universität Zürich, Zürich, CH 8057, Switzerland
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10
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Superhydrophobic self-similar nonwoven-titanate nanostructured materials. J Colloid Interface Sci 2021; 598:93-103. [PMID: 33894618 DOI: 10.1016/j.jcis.2021.03.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/07/2021] [Accepted: 03/08/2021] [Indexed: 11/22/2022]
Abstract
HYPOTHESIS Self-similarity is a scale-invariant irregularity that can assist in designing a robust superhydrophobic material. A combinatorial design strategy involving self-similarity and dual-length scale can be employed to create a new library of a doubly re-entrant, disordered, and porous network of superhydrophobic materials. Asymmetric wettability can be engineered in nonwoven materials by rendering them with superhydrophobic characteristics on one side. EXPERIMENTS A facile, scalable, and inexpensive spray-coating technique was used to decorate the weakly hydrophobicstearate-treatedtitanate nanowires (TiONWs)over the self-similar nonwoven material. Laser scanning confocal microscopy was employed to image the impalement dynamics in three dimensions. With the aid of X-ray microcomputed tomography analysis, the three-dimensional (3D) nonwoven structural parameters were obtained and analyzed. The underwater superhydrophobic behavior of the prepared samples was investigated. FINDINGS A classic 'lotus effect' has been successfully endowed in self-similar nonwoven-titanate nanostructured materials (SS-Ti-NMs) from a nonwoven material that housed the air pockets in bulk and water repellent TiONWs on the surface. The finer fiber-based SS-Ti-NMs exhibited lower roll-off angles and a thinner layer of water on its surface. An asymmetric wettability and the unusual display of underwater superhydrophobic behavior of SS-Ti-NMs have been uncovered.
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11
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Zhao B, Jia Y, Xu Y, Bonaccurso E, Deng X, Auernhammer GK, Chen L. What Can Probing Liquid-Air Menisci Inside Nanopores Teach Us About Macroscopic Wetting Phenomena? ACS APPLIED MATERIALS & INTERFACES 2021; 13:6897-6905. [PMID: 33523651 DOI: 10.1021/acsami.0c21736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Solid surfaces with excellent nonwetting ability have drawn significant interest from interfacial scientists and engineers. While much effort was devoted to investigating macroscopic wetting phenomena on nonwetting surfaces, the otherwise microscopic wetting has received less attention, and the surface/interface properties at the microscopic scale are not well resolved and correlated with the macroscopic wetting behavior. Herein, we first characterize the nanoscopic morphology and effective stiffness of liquid-air interfaces inside nanopores (nanomenisci) on diverse nonwetting nanoporous surfaces underneath water droplets using atomic force microscopy. Detailed three-dimensional imaging of the droplet-surface contact region reveals that water only slightly penetrates into the nanopores, allowing for quantitative prediction of the macroscopic contact angle using the Cassie-Baxter model. By gradually increasing the scanning force, we observe incrementally wetting of nanopores by water, and dewetting occurs when the force is lowered again, exhibiting reversible wetting-dewetting transitions. Further, nanoindentation measurements demonstrate that the nanomenisci show apparent elastic deformation and size-dependent effective stiffness at small indenting forces. Finally, we correlate the effective stiffness of the nanomenisci with the transition from complete rebound to partial rebound for impinging droplets on nanoporous surfaces. Our study suggests that probing the physical properties of the liquid-air menisci at the nanoscale is essential to rationalize macroscopic static and dynamic wetting phenomena on structured surfaces.
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Affiliation(s)
- Binyu Zhao
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
- Leibniz Institute of Polymer Research Dresden, Dresden 01069, Germany
| | - Youquan Jia
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Yi Xu
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
| | | | - Xu Deng
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Günter K Auernhammer
- Leibniz Institute of Polymer Research Dresden, Dresden 01069, Germany
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Longquan Chen
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
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12
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Fickel B, Postulka N, Hartmann M, Gründing DM, Nau M, Meckel T, Biesalski M. Changes of meniscus shapes and capillary rise heights under hypergravity. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2020.125688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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13
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Kumar M, Bhardwaj R, Sahu KC. Wetting Dynamics of a Water Droplet on Micropillar Surfaces with Radially Varying Pitches. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:5312-5323. [PMID: 32356997 DOI: 10.1021/acs.langmuir.0c00697] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The wetting dynamics of a sessile droplet on square micropillar substrates with radially varying pitches, prepared on silicon wafers using a photolithography technique, is investigated experimentally. Two configurations are considered, namely, substrates with radially increasing pitch and radially decreasing pitch. The droplet initially placed at the center experiences a wettability gradient because of the variation in pitch of the micropillar substrate leading to complex wetting dynamics. We observed that the droplet remains in the Cassie-Baxter state in the case of a radially increasing pitch and exhibits a higher contact angle than that on a smooth surface during its spreading stage. In contrast, the droplet experiences the Wenzel condition in the case of a radially decreasing pitch and assumes a lower contact angle relative to that observed on a smooth surface. The wetted diameter of the droplet in the radially decreasing pitch configuration is found to be smaller than that observed in the radially increasing pitch configuration. Our study also reveals that increasing the size of the pillars increases the wetted diameter of the droplet in both configurations. Theoretical models developed using the Cassie-Baxter and Wenzel states for the radially increasing and radially decreasing pitches satisfactorily predict the experimental behaviors.
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Affiliation(s)
- Manish Kumar
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Kirti Chandra Sahu
- Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502 285, Telangana, India
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14
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de Souza Lima R, Ré MI, Arlabosse P. Drying droplet as a template for solid formation: A review. POWDER TECHNOL 2020. [DOI: 10.1016/j.powtec.2019.09.052] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Gerlach F, Hartmann M, Tropea C. The interaction of inner and outer surface corners during spontaneous wetting. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2019.123977] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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16
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Eriksson M, Claesson PM, Järn M, Tuominen M, Wallqvist V, Schoelkopf J, Gane PAC, Swerin A. Wetting Transition on Liquid-Repellent Surfaces Probed by Surface Force Measurements and Confocal Imaging. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:13275-13285. [PMID: 31547659 DOI: 10.1021/acs.langmuir.9b02368] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Superhydrophobic surfaces in the Cassie-Baxter wetting state retain an air layer at the surface which prevents liquid water from reaching into the porous surface structure. In this work we explore how addition of ethanol, which reduces the surface tension, influences the wetting properties of superhydrophobic and smooth hydrophobic surfaces. Wetting properties are measured by dynamic contact angles, and the air layer at the superhydrophobic surface is visualized by laser scanning confocal microscopy. Colloidal probe atomic force microscopy measurements between a hydrophobic microsphere and the macroscopic surfaces showed that the presence of ethanol strongly affects the interaction forces. When the macroscopic surface is superhydrophobic, attractive forces extending up to a few micrometers are observed on retraction in water and in 20 vol % ethanol, signifying the presence of a large and growing gas capillary. Submicrometer attractive forces are observed between the probe particle and a smooth hydrophobic surface, and in this case a smaller gas capillary is formed. Addition of ethanol results in markedly different effects between superhydrophobic and hydrophobic surfaces. In particular, we show that the receding contact angle on the superhydrophobic surface is of paramount importance for describing the interaction forces.
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Affiliation(s)
- Mimmi Eriksson
- RISE Research Institutes of Sweden , SE-11486 Stockholm , Sweden
- School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Chemistry, Division of Surface and Corrosion Science , KTH Royal Institute of Technology , SE-10044 Stockholm , Sweden
| | - Per Martin Claesson
- RISE Research Institutes of Sweden , SE-11486 Stockholm , Sweden
- School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Chemistry, Division of Surface and Corrosion Science , KTH Royal Institute of Technology , SE-10044 Stockholm , Sweden
| | - Mikael Järn
- RISE Research Institutes of Sweden , SE-11486 Stockholm , Sweden
| | - Mikko Tuominen
- RISE Research Institutes of Sweden , SE-11486 Stockholm , Sweden
| | - Viveca Wallqvist
- RISE Research Institutes of Sweden , SE-11486 Stockholm , Sweden
| | | | - Patrick A C Gane
- School of Chemical Engineering, Department of Bioproducts and Biosystems , Aalto University , FI-00076 Aalto , Finland
| | - Agne Swerin
- School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Chemistry, Division of Surface and Corrosion Science , KTH Royal Institute of Technology , SE-10044 Stockholm , Sweden
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17
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Mu L, Yoshikawa HN, Zoueshtiagh F, Ogawa T, Motosuke M, Ueno I. Quick Liquid Propagation on a Linear Array of Micropillars. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:9139-9145. [PMID: 31203626 DOI: 10.1021/acs.langmuir.9b00882] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The wetting process of a high energy surface can be accelerated locally through the capillary interaction of a liquid advancing front with a micro-object introduced to the surface (Mu et al., J. Fluid Mech, 2017, 830, R1). We demonstrate that a linear array of micropillars embedded in a fully wettable substrate can produce quick propagation of liquid along the array. It is observed that multiple interactions of a liquid front with pillars can induce the motion of liquid a hundred times faster than in the absence of pillars.
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Affiliation(s)
- Lizhong Mu
- Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering , Dalian University of Technology , 2 Linggong Road , Ganjinzi District, Dalian 116024 , China
- Research Institute for Science & Technology , Tokyo University of Science , 2641 Yamazaki, Noda , Chiba 278-8510 , Japan
| | - Harunori N Yoshikawa
- Université Côte d'Azur, CNRS, Institut de Physique de Nice , 06100 Nice , France
| | - Farzam Zoueshtiagh
- Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520-IEMN , F-59000 Lille , France
| | - Tetsuya Ogawa
- Division of Mechanical Engineering, Graduate School of Science & Technology , Tokyo University of Science , 2641 Yamazaki, Noda , Chiba 278-8510 , Japan
| | - Masahiro Motosuke
- Department of Mechanical Engineering, Faculty of Engineering , Tokyo University of Science , 6-3-1 Niijuku , Katsushika , Tokyo 125-8585 , Japan
| | - Ichiro Ueno
- Department Mechanical Engineering, Faculty of Science and Technology , Tokyo University of Science , 2641 Yamazaki , Noda, Chiba 278-8510 , Japan
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18
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Eriksson M, Tuominen M, Järn M, Claesson PM, Wallqvist V, Butt HJ, Vollmer D, Kappl M, Schoelkopf J, Gane PAC, Teisala H, Swerin A. Direct Observation of Gas Meniscus Formation on a Superhydrophobic Surface. ACS NANO 2019; 13:2246-2252. [PMID: 30707561 DOI: 10.1021/acsnano.8b08922] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The formation of a bridging gas meniscus via cavitation or nanobubbles is considered the most likely origin of the submicrometer long-range attractive forces measured between hydrophobic surfaces in aqueous solution. However, the dynamics of the formation and evolution of the gas meniscus is still under debate, in particular, in the presence of a thin air layer on a superhydrophobic surface. On superhydrophobic surfaces the range can even exceed 10 μm. Here, we report microscopic images of the formation and growth of a gas meniscus during force measurements between a superhydrophobic surface and a hydrophobic microsphere immersed in water. This is achieved by combining laser scanning confocal microscopy and colloidal probe atomic force microscopy. The configuration allows determination of the volume and shape of the meniscus, together with direct calculation of the Young-Laplace capillary pressure. The long-range attractive interactions acting on separation are due to meniscus formation and volume growth as air is transported from the surface layer.
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Affiliation(s)
- Mimmi Eriksson
- RISE Research Institutes of Sweden , Bioscience and Materials - Surface, Process and Formulation , SE-114 86 Stockholm , Sweden
| | - Mikko Tuominen
- RISE Research Institutes of Sweden , Bioscience and Materials - Surface, Process and Formulation , SE-114 86 Stockholm , Sweden
| | - Mikael Järn
- RISE Research Institutes of Sweden , Bioscience and Materials - Surface, Process and Formulation , SE-114 86 Stockholm , Sweden
| | - Per Martin Claesson
- RISE Research Institutes of Sweden , Bioscience and Materials - Surface, Process and Formulation , SE-114 86 Stockholm , Sweden
- KTH Royal Institute of Technology , School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Chemistry, Division of Surface and Corrosion Science , SE-100 44 Stockholm , Sweden
| | - Viveca Wallqvist
- RISE Research Institutes of Sweden , Bioscience and Materials - Surface, Process and Formulation , SE-114 86 Stockholm , Sweden
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research , Department of Physics at Interfaces , Ackermannweg 10 , DE-55128 Mainz , Germany
| | - Doris Vollmer
- Max Planck Institute for Polymer Research , Department of Physics at Interfaces , Ackermannweg 10 , DE-55128 Mainz , Germany
| | - Michael Kappl
- Max Planck Institute for Polymer Research , Department of Physics at Interfaces , Ackermannweg 10 , DE-55128 Mainz , Germany
| | - Joachim Schoelkopf
- Omya International AG , Baslerstrasse 42 , CH-4665 Oftringen , Switzerland
| | - Patrick A C Gane
- Omya International AG , Baslerstrasse 42 , CH-4665 Oftringen , Switzerland
- Aalto University , School of Chemical Engineering, Department of Bioproducts and Biosystems , FI-00076 Aalto , Finland
| | - Hannu Teisala
- Max Planck Institute for Polymer Research , Department of Physics at Interfaces , Ackermannweg 10 , DE-55128 Mainz , Germany
| | - Agne Swerin
- RISE Research Institutes of Sweden , Bioscience and Materials - Surface, Process and Formulation , SE-114 86 Stockholm , Sweden
- KTH Royal Institute of Technology , School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Chemistry, Division of Surface and Corrosion Science , SE-100 44 Stockholm , Sweden
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19
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Lightweight Porous Glass Composite Materials Based on Capillary Suspensions. MATERIALS 2019; 12:ma12040619. [PMID: 30791420 PMCID: PMC6416639 DOI: 10.3390/ma12040619] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/08/2019] [Accepted: 02/13/2019] [Indexed: 11/17/2022]
Abstract
In this article, we present a simple, advanced method to produce lightweight tailor-made materials based on capillary suspensions that are made from locally bonded hollow glass spheres with a high total porosity in the range of 70% at apparent densities of 200 kg/m3, having a compressive strength of 0.6 MPa. The amount of added liquid and the particle surface treatment determine the network structure in the pastes and the resulting microstructure of the porous material in a straightforward manner. This structure has a strong impact on the porosity, pore size, and mechanical properties of the final body. The most promising porous materials were made of surface treated hollow glass spheres that create a sample-spanning network in the capillary state, where the added liquid wets the particles worse than the bulk fluid. These samples approach the density of natural balsa wood and they may find application in fields where either weight or structure are important, such as in insulation materials, filters, and membranes, as well as lightweight construction materials for automotive or aerospace engineering.
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20
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Papadopoulos P, Pinchasik BE, Tress M, Vollmer D, Kappl M, Butt HJ. Wetting of soft superhydrophobic micropillar arrays. SOFT MATTER 2018; 14:7429-7434. [PMID: 30183043 PMCID: PMC6192145 DOI: 10.1039/c8sm01333k] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 08/24/2018] [Indexed: 05/26/2023]
Abstract
Superhydrophobic surfaces are usually assumed to be rigid so that liquids do not deform them. Here we analyze how the relation between microstructure and wetting changes when the surface is flexible. Therefore we deposited liquid drops on arrays of flexible micropillars. We imaged the drop's surface and the bending of micropillars with confocal microscopy and analyzed the deflection of micropillars while the contact line advanced and receded. The deflection is directly proportional to the horizontal component of the capillary force acting on that particular micropillar. In the Cassie or "fakir" state, drops advance by touching down on the next top faces of micropillars, much like on rigid arrays. In contrast, on the receding side the micropillars deform. The main force hindering the slide of a drop is due to pinning at the receding side, while the force on the advancing side is negligible. In the Wenzel state, micropillars were deflected in both receding and advancing states.
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Affiliation(s)
| | | | - Martin Tress
- Department of Chemistry, University of Tennessee, Knoxville, TN, USA
| | - Doris Vollmer
- Max Planck Institute for Polymer Research, Mainz, Germany.
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Mainz, Germany.
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21
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Gojzewski H, Obszarska J, Harlay A, Hempenius MA, Vancso GJ. Designer poly(urea-siloxane) microspheres with controlled modulus and size: Synthesis, morphology, and nanoscale stiffness by AFM. POLYMER 2018. [DOI: 10.1016/j.polymer.2018.07.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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22
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Latikka M, Backholm M, Timonen JV, Ras RH. Wetting of ferrofluids: Phenomena and control. Curr Opin Colloid Interface Sci 2018. [DOI: 10.1016/j.cocis.2018.04.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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23
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Kim T, Kim W. Viscous dewetting of metastable liquid films on substrates with microgrooves. J Colloid Interface Sci 2018. [DOI: 10.1016/j.jcis.2018.02.073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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24
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Haußmann A. Light scattering from sessile water drops and raindrop-shaped glass beads as a validation tool for rainbow simulations. APPLIED OPTICS 2017; 56:G136-G144. [PMID: 29047479 DOI: 10.1364/ao.56.00g136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 05/07/2017] [Indexed: 06/07/2023]
Abstract
The shape deviation of falling raindrops from exact spheres is known to affect the appearance of natural rainbows, e.g., by enhancing the visibility of supernumerary arcs around the top or by creating branching effects known as "twinned rainbows." To check the accuracy of numerical optical models for rainbow scattering from such nonspherical drops, two simple and low-cost experiments are presented in this paper: (1) sessile, i.e., sitting, drops on ultrahydrophobic surfaces, and (2) glass beads in the shape of falling raindrops. The experimental results are compared to polarization-resolved Monte Carlo ray-tracing simulations, with special emphasis on circular polarization, which results from total internal reflections in these nonspherical scatterers.
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25
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Alonso-Redondo E, Gueddida A, Li J, Graczykowski B, Sotomayor Torres CM, Pennec Y, Yang S, Djafari-Rouhani B, Fytas G. Directional elastic wave propagation in high-aspect-ratio photoresist gratings: liquid infiltration and aging. NANOSCALE 2017; 9:2739-2747. [PMID: 28045161 DOI: 10.1039/c6nr08312a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Determination of the mechanical properties of nanostructured soft materials and their composites in a quantitative manner is of great importance to improve the fidelity in their fabrication and to enable the subsequent reliable utility. Here, we report on the characterization of the elastic and photoelastic parameters of a periodic array of nanowalls (grating) by the non-invasive Brillouin light scattering technique and finite element calculations. The resolved elastic vibrational modes in high and low aspect ratio nanowalls reveal quantitative and qualitative differences related to the two-beam interference lithography fabrication and subsequent aging under ambient conditions. The phononic properties, namely the dispersion relations, can be drastically altered by changing the surrounding material of the nanowalls. Here we demonstrate that liquid infiltration turns the phononic function from a single-direction phonon-guiding to an anisotropic propagation along the two orthogonal directions. The susceptibility of the phononic behavior to the infiltrating liquid can be of unusual benefits, such as sensing and alteration of the materials under confinement.
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Affiliation(s)
- E Alonso-Redondo
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - A Gueddida
- Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR-CNRS 8520, UFR de Physique, Université de Lille 1, 59655 Villeneuve d'Ascq, France and LPMR, Département de Physique, Faculté des Sciences, Université Mohamed I, 60000 Oujda, Morocco
| | - J Li
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, USA
| | - B Graczykowski
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and the Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra, Spain
| | - C M Sotomayor Torres
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and the Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra, Spain and ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Y Pennec
- Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR-CNRS 8520, UFR de Physique, Université de Lille 1, 59655 Villeneuve d'Ascq, France
| | - S Yang
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, USA
| | - B Djafari-Rouhani
- Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR-CNRS 8520, UFR de Physique, Université de Lille 1, 59655 Villeneuve d'Ascq, France
| | - G Fytas
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany. and Department of Materials Science, University of Crete and IESL/FORTH, 71110 Heraklion, Greece
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26
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Lloyd BP, Bartlett PN, Wood RJK. Active gas replenishment and sensing of the wetting state in a submerged superhydrophobic surface. SOFT MATTER 2017; 13:1413-1419. [PMID: 28121004 DOI: 10.1039/c6sm02820a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Previously superhydrophobic surfaces have demonstrated effective drag reduction by trapping a lubricious gas layer on the surface with micron-sized hydrophobic features. However, prolonged reduction of drag is hindered by the dissolution of the gas into the surrounding water. This paper demonstrates a novel combination of superhydrophobic surface design and electrochemical control methods which allow quick determination of the wetted area and a gas replenishment mechanism to maintain the desirable gas filled state. Electrochemical impedance spectroscopy is used to measure the capacitance of the surface which is shown to be proportional to the solid/liquid interface area. To maintain a full gas coverage for prolonged periods the surface is held at an electrical potential which leads to hydrogen evolution. In the desired gas filled state the water does not touch the metallic area of the surface, however after gas has dissolved the water touches the metal which closes the electrochemical circuit causing hydrogen to be produced replenishing the gas in the surface and returning to the gas filled state; in this way the system is self-actuating. This type of surface and electrochemical control shows promise for applications where the gas filled state of superhydrophobic surfaces must be maintained when submerged for long periods of time.
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Affiliation(s)
- Ben P Lloyd
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ, UK.
| | | | - Robert J K Wood
- National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ, UK.
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27
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Extrand CW. Remodeling of Super-hydrophobic Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:8608-8612. [PMID: 27541362 DOI: 10.1021/acs.langmuir.6b02292] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An experimental study on the underlying mechanisms of structured super-hydrophobic surfaces was recently published [ Butt, H.-J.; et al. How Water Advances on Superhydrophobic Surfaces. Phys. Rev. Lett. 2016, 116, 096101 . DOI: 10.1103/PhysRevLett.116.096101 ]. After depositing small drops of water, Butt's group inclined their surfaces to initiate movement. They examined the contact between the water and structured surfaces with confocal microscopy. They observed that drops were suspended atop the protruding features and movement of water was different at the advancing and receding edges. At the advancing edge, the water interface descended downward and draped itself across the features. At the receding edge, water jumped from one feature to the next. As Butt and co-workers did not test their data against any existing model, that is done in this paper. Here, a previously proposed model that employs linear averaging at the contact line was adapted to their surfaces in an attempt to estimate their contact and sliding angles. Predictions from the model generally agreed with their experimental measurements.
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Affiliation(s)
- C W Extrand
- CPC , 1001 Westgate Drive, St. Paul, Minnesota 55114, United States
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28
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Zanini M, Isa L. Particle contact angles at fluid interfaces: pushing the boundary beyond hard uniform spherical colloids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:313002. [PMID: 27299800 DOI: 10.1088/0953-8984/28/31/313002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Micro and nanoparticles at fluid interfaces have been attracting increasing interest in the last few decades as building blocks for materials, as mechanical and structural probes for complex interfaces and as models for two-dimensional systems. The three-phase contact angle enters practically all aspects of the particle behavior at the interface: its thermodynamics (binding energy to the interface), dynamics (motion and drag at the interface) and interactions with the interface (adsorption and wetting). Moreover, many interactions among particles at the interface also strongly depend on the contact angle. These concepts have been extensively discussed for non-deformable, homogeneous and mostly spherical particles, but recent progress in particle synthesis and fabrication has instead moved in the direction of producing more complex micro and nanoscale objects, which can be responsive, deformable, heterogenous and/or anisotropic in shape, surface chemistry and material properties. These new particles have a much greater potential for applications and new science, and the study of their behavior at interfaces has only very recently started. In this paper, we critically review the current state of the art of the experimental methods available to measure the contact angle of micro and nanoparticles at fluid interfaces, indicating their strengths and limitations. We then comment on new particle systems that are currently attracting increasing interest in relation to their adsorption and assembly at fluid interfaces and discuss if and which ones of the current techniques are suited to investigate their properties at interfaces. Based on this discussion, we will finally try to indicate a direction in which new experimental methods should develop in the future to tackle the new challenges posed by the novel types of particles that more and more often are used at interfaces.
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Affiliation(s)
- Michele Zanini
- Department of Materials, Laboratory for Interfaces, Soft matter and Assembly, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich, Switzerland
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29
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Abstract
This feature article provides an overview of wetting phenomena. Much of the analysis done on wetting in the last 100 years assumes that the phenomena are determined by molecular interactions within the interfacial area between the liquid and solid. However, there is now ample evidence that wetting is controlled by interactions in the vicinity of the contact line where the liquid and solid meet. Recent experiments and modeling that demonstrate this are reviewed.
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Affiliation(s)
- Charles W Extrand
- CPC, Inc., 1001 Westgate Drive, St. Paul, Minnesota 55114, United States
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30
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Neubauer JW, Xue L, Erath J, Drotlef DM, Campo AD, Fery A. Monitoring the Contact Stress Distribution of Gecko-Inspired Adhesives Using Mechano-Sensitive Surface Coatings. ACS APPLIED MATERIALS & INTERFACES 2016; 8:17870-17877. [PMID: 27327111 DOI: 10.1021/acsami.6b05327] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The contact geometry of microstructured adhesive surfaces is of high relevance for adhesion enhancement. Theoretical considerations indicate that the stress distribution in the contact zone is crucial for the detachment mechanism, but direct experimental evidence is missing so far. In this work, we propose a method that allows, for the first time, the detection of local stresses at the contact area of biomimetic adhesive microstructures during contact formation, compression and detachment. We use a mechano-sensitive polymeric layer, which turns mechanical stresses into changes of fluorescence intensity. The biomimetic surface is brought into contact with this layer in a well-defined fashion using a microcontact printer, while the contact area is monitored with fluorescence microscopy in situ. Thus, changes in stress distribution across the contact area during compression and pull-off can be visualized with a lateral resolution of 1 μm. We apply this method to study the enhanced adhesive performance of T-shaped micropillars, compared to flat punch microstructures. We find significant differences in the stress distribution of the both differing contact geometries during pull-off. In particular, we find direct evidence for the suppression of crack nucleation at the edge of T-shaped pillars, which confirms theoretical models for the superior adhesive properties of these structures.
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Affiliation(s)
- Jens W Neubauer
- Leibniz-Institut für Polymerforschung Dresden e.V. , Hohe Str. 6, 01069 Dresden, Germany
- Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany
| | - Longjian Xue
- School of Power and Mechanical Engineering, Wuhan University , South Donghu Road 8, 430072 Wuhan, China
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Johann Erath
- Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany
| | - Dirk-M Drotlef
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
| | - Aránzazu Del Campo
- Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany
- INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany
- Chemistry Department, Saarland University , 66123 Saarbrücken, Germany
| | - Andreas Fery
- Leibniz-Institut für Polymerforschung Dresden e.V. , Hohe Str. 6, 01069 Dresden, Germany
- Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany
- Cluster of Excellence Centre for Advancing Electronics Dresden (cfaed), Technische Universität Dresden , 01062 Dresden, Germany
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31
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Contraires E, Teisseire J, Søndergård E, Barthel E. Wetting against the nap - how asperity inclination determines unidirectional spreading. SOFT MATTER 2016; 12:6067-6072. [PMID: 27373469 DOI: 10.1039/c6sm00523c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We have carried out wetting experiments on textured surfaces with high aspect ratio asperities in the Wenzel state. When inclination is imparted to the asperities, we observe a strictly unidirectional spreading opposite to the direction in which the asperities point. The advancing contact angle decreases markedly as inclination increases. A crude numerical analysis successfully accounts for this behaviour, highlighting the interplay between Gibbs pinning at the top of the structures and imbibition along the valleys between them. In Gibbs pinning non-linearities play a major role and we find that simple line averaging - i.e. a rule of mixture - cannot account for this evolution except for weak surface perturbations, i.e. large inclinations.
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Affiliation(s)
- Elise Contraires
- Laboratoire de Tribologie et Dynamique des Systèmes, UMR5513, CNRS, Ecole Centrale de Lyon, 36 avenue Guy de Collongue, FR-69134 Ecully cedex, France
| | - Jérémie Teisseire
- Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers, France and PCRS, Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers, France
| | - Elin Søndergård
- Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers, France
| | - Etienne Barthel
- École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI) ParisTech, PSL Research University, Sciences et Ingénierie de la matière Molle, CNRS UMR 7615, 10, Rue Vauquelin, F-75231 Paris Cedex 05, France and Sorbonne-Universités, UPMC Univ. Paris 06, SIMM, 10, Rue Vauquelin, F-75231 Paris Cedex 05, France
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32
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3D Imaging of Water-Drop Condensation on Hydrophobic and Hydrophilic Lubricant-Impregnated Surfaces. Sci Rep 2016; 6:23687. [PMID: 27040483 PMCID: PMC4819200 DOI: 10.1038/srep23687] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 03/08/2016] [Indexed: 11/23/2022] Open
Abstract
Condensation of water from the atmosphere on a solid surface is an ubiquitous phenomenon in nature and has diverse technological applications, e.g. in heat and mass transfer. We investigated the condensation kinetics of water drops on a lubricant-impregnated surface, i.e., a micropillar array impregnated with a non-volatile ionic liquid. Growing and coalescing drops were imaged in 3D using a laser scanning confocal microscope equipped with a temperature and humidity control. Different stages of condensation can be discriminated. On a lubricant-impregnated hydrophobic micropillar array these are: (1) Nucleation on the lubricant surface. (2) Regular alignment of water drops between micropillars and formation of a three-phase contact line on a bottom of the substrate. (3) Deformation and bridging by coalescence which eventually leads to a detachment of the drops from the bottom substrate. The drop-substrate contact does not result in breakdown of the slippery behaviour. Contrary, on a lubricant-impregnated hydrophilic micropillar array, the condensed water drops replace the lubricant. Consequently, the surface loses its slippery property. Our results demonstrate that a Wenzel-like to Cassie transition, required to maintain the facile removal of condensed water drops, can be induced by well-chosen surface hydrophobicity.
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33
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Akerboom S, Kamperman M, Leermakers FAM. Three-gradient regular solution model for simple liquids wetting complex surface topologies. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2016; 7:1377-1396. [PMID: 27826512 PMCID: PMC5082679 DOI: 10.3762/bjnano.7.129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/25/2016] [Indexed: 05/12/2023]
Abstract
We use regular solution theory and implement a three-gradient model for a liquid/vapour system in contact with a complex surface topology to study the shape of a liquid drop in advancing and receding wetting scenarios. More specifically, we study droplets on an inverse opal: spherical cavities in a hexagonal pattern. In line with experimental data, we find that the surface may switch from hydrophilic (contact angle on a smooth surface θY < 90°) to hydrophobic (effective advancing contact angle θ > 90°). Both the Wenzel wetting state, that is cavities under the liquid are filled, as well as the Cassie-Baxter wetting state, that is air entrapment in the cavities under the liquid, were observed using our approach, without a discontinuity in the water front shape or in the water advancing contact angle θ. Therefore, air entrapment cannot be the main reason why the contact angle θ for an advancing water front varies. Rather, the contact line is pinned and curved due to the surface structures, inducing curvature perpendicular to the plane in which the contact angle θ is observed, and the contact line does not move in a continuous way, but via depinning transitions. The pinning is not limited to kinks in the surface with angles θkink smaller than the angle θY. Even for θkink > θY, contact line pinning is found. Therefore, the full 3D-structure of the inverse opal, rather than a simple parameter such as the wetting state or θkink, determines the final observed contact angle.
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Affiliation(s)
- Sabine Akerboom
- Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands
| | - Marleen Kamperman
- Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands
| | - Frans A M Leermakers
- Physical Chemistry and Soft Matter, Wageningen University, Stippeneng 4, 6708 WE Wageningen, Netherlands
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34
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Butt HJ, Vollmer D, Papadopoulos P. Super liquid-repellent layers: The smaller the better. Adv Colloid Interface Sci 2015; 222:104-9. [PMID: 24996450 DOI: 10.1016/j.cis.2014.06.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 06/03/2014] [Accepted: 06/03/2014] [Indexed: 11/29/2022]
Abstract
Super liquid-repellent layers need to have a high impalement pressure and high contact angles, in particular a high apparent receding contact angle. Here, we demonstrate that to achieve both, the features constituting the layer should be as small as possible. Therefore, two models for super liquid-repellent layers are theoretically analyzed: A superhydrophobic layer consisting of an array of cylindrical micropillars and a superamphiphobic layer of an array of pillars of spheres. For the cylindrical micropillars a simple expression for the apparent receding contact angle is derived. It is based on a force balance rather than a thermodynamic approach. The model is supported by confocal microscope images of a water drop on an array of hydrophobic cylindrical pillars. The ratio of the width of a pillar w to the center-to-center spacing a is a primary factor in controlling the receding angle. Keeping the ratio w/a constant, the absolute size of surface features should be as small as possible, to maximize the impalement pressure.
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Affiliation(s)
- Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
| | - Doris Vollmer
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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35
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Detailed statistical contact angle analyses; “slow moving” drops on inclining silicon-oxide surfaces. J Colloid Interface Sci 2015; 447:229-39. [DOI: 10.1016/j.jcis.2014.10.047] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 10/13/2014] [Accepted: 10/15/2014] [Indexed: 11/24/2022]
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36
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Lv P, Xue Y, Liu H, Shi Y, Xi P, Lin H, Duan H. Symmetric and asymmetric meniscus collapse in wetting transition on submerged structured surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:1248-1254. [PMID: 25548941 DOI: 10.1021/la503465q] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The wetting transition from the Cassie-Baxter to the Wenzel state is a phenomenon critically pertinent to the functionality of microstructured superhydrophobic surfaces. This work focuses on the last stage of the transition, when the liquid-gas interface touches the bottom of the microstructure, which is also known as the "collapse" phenomenon. The process was examined in situ on a submerged surface patterned with cylindrical micropores using confocal microscopy. Both symmetric and asymmetric collapses were observed. The latter significantly shortens the progression of the metastable state prior to the collapse when compared with the former and hence may affect the lifespan of superhydrophobicity. Further experiments identified that asymmetric collapse were induced by impurities due to prior use of the structure. The problem is thus of broad relevance, since endurance through cycles is a practical requirement for these functional surfaces. Finally, the use of hierarchical structures is proposed as a remedy. The embedded self-cleaning mechanism serves to effectively remove the impurities, so as to avoid the triggering mechanism for asymmetric collapses.
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Affiliation(s)
- Pengyu Lv
- State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, CAPT, IFSA Collaborative Innovation Center of MoE, College of Engineering and ‡Department of Biomedical Engineering, College of Engineering, Peking University , Beijing 100871, China
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37
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Mammen L, Bley K, Papadopoulos P, Schellenberger F, Encinas N, Butt HJ, Weiss CK, Vollmer D. Functional superhydrophobic surfaces made of Janus micropillars. SOFT MATTER 2015; 11:506-15. [PMID: 25415839 PMCID: PMC4358088 DOI: 10.1039/c4sm02216e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 10/31/2014] [Indexed: 05/26/2023]
Abstract
We demonstrate the fabrication of superhydrophobic surfaces consisting of micropillars with hydrophobic sidewalls and hydrophilic tops, referred to as Janus micropillars. Therefore we first coat a micropillar array with a mono- or bilayer of polymeric particles, and merge the particles together to shield the top faces while hydrophobizing the walls. After removing the polymer film, the top faces of the micropillar arrays can be selectively chemically functionalised with hydrophilic groups. The Janus arrays remain superhydrophobic even after functionalisation as verified by laser scanning confocal microscopy. The robustness of the superhydrophobic behaviour proves that the stability of the entrapped air cushion is determined by the forces acting at the rim of the micropillars. This insight should stimulate a new way of designing super liquid-repellent surfaces with tunable liquid adhesion. In particular, combining superhydrophobicity with the functionalisation of the top faces of the protrusions with hydrophilic groups may have exciting new applications, including high-density microarrays for high-throughput screening of bioactive molecules, cells, or enzymes or efficient water condensation. However, so far chemical attachment of hydrophilic molecules has been accompanied with complete wetting of the surface underneath. The fabrication of superhydrophobic surfaces where the top faces of the protrusions can be selectively chemically post-functionalised with hydrophilic molecules, while retaining their superhydrophobic properties, is both promising and challenging.
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Affiliation(s)
- Lena Mammen
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
| | - Karina Bley
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
| | - Periklis Papadopoulos
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
| | - Frank Schellenberger
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
| | - Noemí Encinas
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
| | - Clemens K. Weiss
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
- University of Applied Sciences Bingen , Berlinstrasse 109 , D-55411 Bingen , Germany
| | - Doris Vollmer
- Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 , Mainz , Germany .
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38
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Schellenberger F, Xie J, Encinas N, Hardy A, Klapper M, Papadopoulos P, Butt HJ, Vollmer D. Direct observation of drops on slippery lubricant-infused surfaces. SOFT MATTER 2015; 11:7617-26. [PMID: 26291621 DOI: 10.1039/c5sm01809a] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Water droplet resting on a slippery surface.
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Affiliation(s)
| | - Jing Xie
- Max Planck Institute for Polymer Research
- 55128 Mainz, Germany
| | - Noemí Encinas
- Max Planck Institute for Polymer Research
- 55128 Mainz, Germany
| | - Alexandre Hardy
- Max Planck Institute for Polymer Research
- 55128 Mainz, Germany
| | - Markus Klapper
- Max Planck Institute for Polymer Research
- 55128 Mainz, Germany
| | | | | | - Doris Vollmer
- Max Planck Institute for Polymer Research
- 55128 Mainz, Germany
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39
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40
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Extrand CW, Moon SI. Repellency of the lotus leaf: contact angles, drop retention, and sliding angles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8791-7. [PMID: 25029189 DOI: 10.1021/la5019482] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Much of the modeling done on repellency and super hydrophobicity has focused on surfaces with rectilinear geometries, but their wetting behavior is simpler and can be quite different from that of repellent surfaces with curved features. In this study, we model the contact angles and sliding angles exhibited by the lotus leaf, accounting for the influence of curvature and pinning. Our estimates agree reasonably well with experimental observations.
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Affiliation(s)
- C W Extrand
- Entegris, Inc. , 101 Peavey Road, Chaska, Minnesota 55318, United States
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41
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Kanungo M, Mettu S, Law KY, Daniel S. Effect of roughness geometry on wetting and dewetting of rough PDMS surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:7358-7368. [PMID: 24911256 DOI: 10.1021/la404343n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Rough PDMS surfaces comprising 3 μm hemispherical bumps and cavities with pitches ranging from 4.5 to 96 μm have been fabricated by photolithographic and molding techniques. Their wetting and dewetting behavior with water was studied as model for print surfaces used in additive manufacturing and printed electronics. A smooth PDMS surface was studied as control. For a given pitch, both bumpy and cavity surfaces exhibit similar static contact angles, which increase as the roughness ratio increases. Notably, the observed water contact angles are shown to be consistently larger than the calculated Wenzel angles, attributable to the pinning of the water droplets into the metastable wetting states. Optical microscopy reveals that the contact lines on both the bumpy and cavity surfaces are distorted by the microtextures, pinning at the lead edges of the bumps and cavities. Vibration of the sessile droplets on the smooth, bumpy, and cavity PDMS surfaces results in the same contact angle, from 110°-124° to ∼91°. The results suggest that all three surfaces have the same stable wetting states after vibration and that water droplets pin in the smooth area of the rough PDMS surfaces. This conclusion is supported by visual inspection of the contact lines before and after vibration. The importance of pinning location rather than surface energy on the contact angle is discussed. The dewetting of the water droplet was studied by examining the receding motion of the contact line by evaporating the sessile droplets of a very dilute rhodamine dye solution on these surfaces. The results reveal that the contact line is dragged by the bumps as it recedes, whereas dragging is not visible on the smooth and the cavity surfaces. The drag created by the bumps toward the wetting and dewetting process is also visible in the velocity-dependent advancing and receding contact angle experiments.
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Affiliation(s)
- Mandakini Kanungo
- Xerox Corporation Xerox Research Center, Webster 800 Phillips Rd, 147-59B, Webster, New York 14580, United States
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42
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Cheng Y, Suhonen H, Helfen L, Li J, Xu F, Grunze M, Levkin PA, Baumbach T. Direct three-dimensional imaging of polymer-water interfaces by nanoscale hard X-ray phase tomography. SOFT MATTER 2014; 10:2982-2990. [PMID: 24695753 DOI: 10.1039/c3sm52604f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report three-dimensional (3D) direct imaging of complex surface-liquid interfaces by hard X-ray phase contrast tomography as a non-destructive approach for the morphological characterization of surfaces at the micro- and nanoscale in contact with water. Specifically, we apply this method to study the solid-air-water interface in hydrophobic macroporous polymethacrylate surfaces, and the solid-oil-water interface in slippery liquid-infused porous surfaces (SLIPS). Varying the isotropic spatial resolution allows the 3D quantitative characterization of individual polymer globules, globular clusters (porosity) as well as the infused lubricant layer on SLIPS. Surface defects were resolved at the globular level. We show the first application of X-ray nanotomography to hydrated surface characterizations and we anticipate that X-ray nanoscale imaging will open new ways for various surface/interface studies.
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Affiliation(s)
- Yin Cheng
- Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), D-76344 Karlsruhe, Germany.
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43
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Ben Said M, Selzer M, Nestler B, Braun D, Greiner C, Garcke H. A phase-field approach for wetting phenomena of multiphase droplets on solid surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4033-4039. [PMID: 24673164 DOI: 10.1021/la500312q] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study the equilibrium wetting behavior of immiscible multiphase systems on a flat, solid substrate. We present numerical computations which are based on a vector-valued multiphase-field model of Allen-Cahn type, with a new boundary condition, based on appropriately designed surface energy contributions in order to ensure the right contact angles at multiphase junctions. Experimental investigations are carried out to validate the method and to support the numerical results.
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Affiliation(s)
- Marouen Ben Said
- Institute of Applied Materials, Karlsruhe Institute of Technology , 76131 Karlsruhe, Germany
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44
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Bellanger H, Darmanin T, Taffin de Givenchy E, Guittard F. Chemical and physical pathways for the preparation of superoleophobic surfaces and related wetting theories. Chem Rev 2014; 114:2694-716. [PMID: 24405122 DOI: 10.1021/cr400169m] [Citation(s) in RCA: 243] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Hervé Bellanger
- Univ. Nice Sophia Antipolis , CNRS, LPMC, UMR 7336, 06100 Nice, France
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45
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Zhang Z, Kim H, Ha MY, Jang J. Molecular dynamics study on the wettability of a hydrophobic surface textured with nanoscale pillars. Phys Chem Chem Phys 2014; 16:5613-21. [PMID: 24513852 DOI: 10.1039/c3cp54976c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Zhengqing Zhang
- Department of Nanomaterials Engineering, Pusan National University, Busan 609-735, Republic of Korea.
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46
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Sadek C, Tabuteau H, Schuck P, Fallourd Y, Pradeau N, Le Floch-Fouéré C, Jeantet R. Shape, shell, and vacuole formation during the drying of a single concentrated whey protein droplet. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15606-15613. [PMID: 24261716 DOI: 10.1021/la404108v] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The drying of milk concentrate droplets usually leads to specific particle morphology influencing their properties and their functionality. Understanding how the final shape of the particle is formed therefore represents a key issue for industrial applications. In this study, a new approach to the investigation of droplet-particle conversion is proposed. A single droplet of concentrated globular proteins extracted from milk was deposited onto a hydrophobic substrate and placed in a dry environment. Complementary methods (high-speed camera, confocal microscopy, and microbalance) were used to record the drying behavior of the concentrated protein droplets. Our results showed that whatever the initial concentration, particle formation included three dynamic stages clearly defined by the loss of mass and the evolution of the internal and external shapes of the droplet. A new and reproducible particle shape was related in this study. It was observed after drying a smooth, hemispherical cap-shaped particle, including a uniform protein shell and the nucleation of an internal vacuole. The particle morphology was strongly influenced by the drying environment, the contact angle, and the initial protein concentration, all of which governed the duration of the droplet shrinkage, the degree of buckling, and the shell thickness. These results are discussed in terms of specific protein behaviors in forming a predictable and a characteristic particle shape. The way the shell is formed may be the starting point in shaping particle distortion and thus represents a potential means of tuning the particle morphology.
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47
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Zuruzi AS, Yeo YH, Monkowski AJ, Ding CS, MacDonald NC. Superhydrophilicity on microstructured titanium surfaces via a superficial titania layer with interconnected nanoscale pores. NANOTECHNOLOGY 2013; 24:245304. [PMID: 23690071 DOI: 10.1088/0957-4484/24/24/245304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Microstructured titanium (Ti) surfaces often suffer from poor hydrophilicity which makes the realization of open microfluidic devices difficult. Here, we investigate the effect of a superficial porous titania (TiO2) layer on the hydrophilicity of microstructured surfaces. High aspect ratio Ti micropillars were micromachined from bulk Ti sheets. Porous TiO2 was subsequently grown on Ti micropillars by a wet oxidation route followed by thermal annealing. Porous TiO2 was characterized using atomic force microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. Detailed morphology study and pore size analysis were carried using focused ion beam machining coupled with scanning electron microscopy. Static contact angle and dynamic spreading studies clearly demonstrate enhanced hydrophilicity of microstructured Ti surfaces with a superficial porous TiO2 layer. Such enhancement promises interesting applications in the microfluidics and microsystems fields.
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48
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Papadopoulos P, Mammen L, Deng X, Vollmer D, Butt HJ. How superhydrophobicity breaks down. Proc Natl Acad Sci U S A 2013; 110:3254-8. [PMID: 23382197 PMCID: PMC3587223 DOI: 10.1073/pnas.1218673110] [Citation(s) in RCA: 249] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A droplet deposited or impacting on a superhydrophobic surface rolls off easily, leaving the surface dry and clean. This remarkable property is due to a surface structure that favors the entrainment of air cushions beneath the drop, leading to the so-called Cassie state. The Cassie state competes with the Wenzel (impaled) state, in which the liquid fully wets the substrate. To use superhydrophobicity, impalement of the drop into the surface structure needs to be prevented. To understand the underlying processes, we image the impalement dynamics in three dimensions by confocal microscopy. While the drop evaporates from a pillar array, its rim recedes via stepwise depinning from the edge of the pillars. Before depinning, finger-like necks form due to adhesion of the drop at the pillar's circumference. Once the pressure becomes too high, or the drop too small, the drop slowly impales the texture. The thickness of the air cushion decreases gradually. As soon as the water-air interface touches the substrate, complete wetting proceeds within milliseconds. This visualization of the impalement dynamics will facilitate the development and characterization of superhydrophobic surfaces.
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Affiliation(s)
- Periklis Papadopoulos
- Physics at Interfaces, Max Planck Institute for Polymer Research, D-55128 Mainz, Germany
| | - Lena Mammen
- Physics at Interfaces, Max Planck Institute for Polymer Research, D-55128 Mainz, Germany
| | - Xu Deng
- Physics at Interfaces, Max Planck Institute for Polymer Research, D-55128 Mainz, Germany
| | - Doris Vollmer
- Physics at Interfaces, Max Planck Institute for Polymer Research, D-55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Physics at Interfaces, Max Planck Institute for Polymer Research, D-55128 Mainz, Germany
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49
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Li X, Mao L, Ma X. Dynamic behavior of water droplet impact on microtextured surfaces: the effect of geometrical parameters on anisotropic wetting and the maximum spreading diameter. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:1129-1138. [PMID: 23265312 DOI: 10.1021/la304567s] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Textured silicon surfaces decorated by square arrays of pillars with adjustable pitch were fabricated. The wetting behavior, especially for direction-dependent water contact angles on textured silicon surfaces after silanization, was investigated by incorporating the contact line fraction into a modified Wenzel model. Also, the effect of geometrical parameters on the anisotropic wetting behavior of water was examined with respect to water droplet impact on the textured surface. Moreover, the maximum spreading factor was studied theoretically in terms of energy conservation, allowing for surface topography and viscous friction of the liquid flowing among the arrays of the posts. Theoretical models were found to be in good agreement with experimental data.
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Affiliation(s)
- Xiying Li
- Institute of Fine Chemistry and Engineering, Henan University, Kaifeng, 475001, China.
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50
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Paxson AT, Varanasi KK. Self-similarity of contact line depinning from textured surfaces. Nat Commun 2013; 4:1492. [PMID: 23422660 PMCID: PMC3586717 DOI: 10.1038/ncomms2482] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 01/14/2013] [Indexed: 11/28/2022] Open
Abstract
The mobility of drops on surfaces is important in many biological and industrial processes, but the phenomena governing their adhesion, which is dictated by the morphology of the three-phase contact line, remain unclear. Here we describe a technique for measuring the dynamic behaviour of the three-phase contact line at micron length scales using environmental scanning electron microscopy. We examine a superhydrophobic surface on which a drop's adhesion is governed by capillary bridges at the receding contact line. We measure the microscale receding contact angle of each bridge and show that the Gibbs criterion is satisfied at the microscale. We reveal a hitherto unknown self-similar depinning mechanism that shows how some hierarchical textures such as lotus leaves lead to reduced pinning, and counter-intuitively, how some lead to increased pinning. We develop a model to predict adhesion force and experimentally verify the model's broad applicability on both synthetic and natural textured surfaces.
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Affiliation(s)
- Adam T. Paxson
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Kripa K. Varanasi
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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