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Zhang S, Zhao L, Yu M, Guo J, Liu C, Zhu C, Zhao M, Huang Y, Zheng Y. Measurement Methods for Droplet Adhesion Characteristics and Micrometer-Scale Quantification of Contact Angle on Superhydrophobic Surfaces: Challenges and Opportunities. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:9873-9891. [PMID: 38695884 DOI: 10.1021/acs.langmuir.3c03967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2024]
Abstract
Inspired by nature, superhydrophobic surfaces have been widely studied. Usually the wettability of a superhydrophobic surface is quantified by the macroscopic contact angle. However, this method has various limitations, especially for precision micro devices with superhydrophobic surfaces, such as biomimetic artificial compound eyes and biomimetic water strider robots. These precision micro devices with superhydrophobic surfaces proposed a higher demand for the quantification of contact angles, requiring contact angle quantification technology to have micrometer-scale measurement capabilities. In this review, it is proposed to achieve micrometer-scale quantification of superhydrophobic surface contact angles through droplet adhesion characteristics (adhesion force and contact radius). Existing contact angle quantification techniques and droplet characteristics' measurement methods were described in detail. The advancement of micrometer-scale quantification technology for the contact angle of superhydrophobic surfaces will enhance our understanding of superhydrophobic surfaces.
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Affiliation(s)
- Shiyu Zhang
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Lingzhe Zhao
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Meike Yu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Jinwei Guo
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Chuntian Liu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Chunyuan Zhu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Meirong Zhao
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Yinguo Huang
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Yelong Zheng
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
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Varghese N, Sykes TC, Quetzeri-Santiago MA, Castrejón-Pita AA, Castrejón-Pita JR. Effect of Surfactants on the Splashing Dynamics of Drops Impacting Smooth Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:8781-8790. [PMID: 38444249 PMCID: PMC11064227 DOI: 10.1021/acs.langmuir.3c03248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 02/16/2024] [Accepted: 02/21/2024] [Indexed: 03/07/2024]
Abstract
We present the results of a systematic study elucidating the role that dynamic surface tension has on the spreading and splashing dynamics of surfactant-laden droplets during the impact on hydrophobic substrates. Using four different surfactants at various concentrations, we generated a range of solutions whose dynamic surface tension were characterized to submillisecond timescales using maximum bubble-pressure tensiometry. Impact dynamics of these solutions were observed by high-speed imaging with subsequent quantitative image processing to determine the impact parameters (droplet size and speed) and dynamic wetting properties (dynamic contact angle). Droplets were slowly formed by dripping to allow the surfactants to achieve equilibrium at the free surface prior to impact. Our results indicate that while only the fastest surfactants appreciably affect the maximum spreading diameter, the droplet morphology during the initial stages of spreading is different to water for all surfactant solutions studied. Moreover, we show that surfactant-laden droplets splash more easily than pure liquid (water). Based on the association of the splashing ratio to our tensiometry measurements, we are able to predict the effective surface tension acting during splashing. These results suggest that droplet splashing characteristics are primarily defined by the stretching of the equilibrated droplet free surface.
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Affiliation(s)
- Nonu Varghese
- School
of Engineering and Material Sciences, Queen
Mary University of London, London, E1 4NS, U.K.
- Department
of Mechanical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Thomas C. Sykes
- Department
of Engineering Science, University of Oxford, Oxford OX1 3PJ, U.K.
| | - Miguel A. Quetzeri-Santiago
- Department
of Engineering Science, University of Oxford, Oxford OX1 3PJ, U.K.
- Instituto
de Investigaciones en Materiales, Universidad Nacional Autónoma
de México, Cd. Universitaria, Mexico City 04530, Mexico
| | | | - J. Rafael Castrejón-Pita
- Department
of Mechanical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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Yang L, Liu X, Wang J, Zhang P. An Experimental Study on Complete Droplet Rebound from Soft Surfaces: Critical Weber Numbers, Maximum Spreading, and Contact Time. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:2165-2173. [PMID: 38232322 DOI: 10.1021/acs.langmuir.3c03126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Droplet impact on soft surfaces (PDMS) was experimentally studied with particular interest in the complete rebound of droplets. This study focuses on the effect of liquid viscosity and the elastic modulus of the substrate on the critical rebound Weber number, maximum spreading, and contact time. Specifically, the lower and upper critical Weber numbers increase with an increasing droplet viscosity. With decreasing PDMS elastic modulus, the upper critical Weber number increases, while the lower critical Weber number decreases. The PDMS elastic modulus does not significantly affect the maximum spreading time and contact time. An interesting phenomenon of discontinuous contact time was experimentally observed and was theoretically interpreted.
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Affiliation(s)
- Lei Yang
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China
| | - Ximiao Liu
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China
| | - Jinyang Wang
- State Key Laboratory of Engines, Tianjin University, Tianjin 300350, PR China
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon 999077, Hong Kong
| | - Peng Zhang
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon 999077, Hong Kong
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Fan Y, Wang Y. Deposition and Spread of Aqueous Pesticide Droplets on Hydrophobic/Superhydrophobic Surfaces by Fast Aggregation of Surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5631-5640. [PMID: 37053578 DOI: 10.1021/acs.langmuir.3c00282] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Deposition and spread of aqueous droplets on hydrophobic/superhydrophobic surfaces are of great significance in many practical applications, such as spraying, coating, and printing, and particularly in improving pesticide utilization efficiency because the intrinsic hydrophobicity/superhydrophobicity of most plant leaves results in serious loss of water-based pesticides during spraying. It has been found that proper surfactants can promote the droplet spread on such surfaces. However, most reports involved the effects of surfactants on the spread of the gently released droplets over hydrophobic or highly hydrophobic substrates, while the situation on superhydrophobic substrates has rarely been explored. Moreover, high-speed impact makes it extremely difficult to deposit and spread the aqueous droplets on superhydrophobic surfaces; thus, the deposition and spread have just been achieved by surfactants in recent years. Here, we give an overview concerning the influence factors on the deposition and spreading performance of gently released and high-speed impacted droplets on hydrophobic/superhydrophobic substrates and emphasize the effects of fast aggregation of surfactants at the interface and in solution. We also outline perspectives on the future development of surfactant-assisted deposition and spreading after high-speed impact.
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Affiliation(s)
- Yaxun Fan
- CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Yilin Wang
- CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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Zhao R, Yu M, Sun Z, Li LJ, Guo XY, Xu Y, Wu XM. Regulating droplet impact and wetting behaviors on hydrophobic leaves using a nonionic surfactant. J Colloid Interface Sci 2023; 629:926-937. [DOI: 10.1016/j.jcis.2022.08.179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/14/2022] [Accepted: 08/29/2022] [Indexed: 11/15/2022]
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Esmaeili AR, Meisoll G, Mir N, Mohammadi R. On the droplet impact dynamics of nonionic surfactant solutions on non-wettable coatings. J Colloid Interface Sci 2022. [DOI: 10.1016/j.jcis.2022.05.097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Yang C, Cao W, Yang Z. Study on dynamic behavior of water droplet impacting on super-hydrophobic surface with micro-pillar structures by VOF method. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127634] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Li T, Wu Y. Impact Dynamics of Nanodroplets on V-Shaped Substrates: Asymmetrical Behavior and Fast-Rebound Dynamics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:13170-13178. [PMID: 34699717 DOI: 10.1021/acs.langmuir.1c02488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Controlling the drop impact behaviors plays an important role in both designing surface functional materials and improving industrial techniques. Here, the impact dynamics of nanodroplets on "V-shaped" substrates is studied, which is manifested as asymmetrical spreading and retraction behaviors that could be weakened by increasing the angles of the "V" shape, accompanied by the evolution of the shape from leaf-like, stripe-like, to dumbbell-like at v = 20 Å/ps. When v increases to 40 Å/ps, the previously deposited nanodroplets could be transformed to a rebound one at α = 60 and 90°, which is ascribed to the combined effect of the confinement conditions and the extrusion force. Furthermore, an impact behavior map as a function of impact velocity and angle is depicted, which suggests that a decrease in angles or an increase in the impact velocity is likely to cause the nanodroplets to rebound. More importantly, the results give visible evidence that compared to the flat substrates, the V-shaped structure is advantageous for achieving a fast-rebound behavior even at a low speed of impact, which should be good news for practical applications in many multidisciplinary fields, such as self-cleaning, anti-icing/fogging, pollution prevention, energy storage, and so forth.
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Affiliation(s)
- Tao Li
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China
| | - Yan Wu
- Department of Chemistry, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 999077, China
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Li Z, Li Z, Gao Y, Zhang C, Zhao K, Guo Y, Bao Z, Wu T, Li X, Du F. Assemblies disaggregation and diffusion dictated droplet impact and wetting behaviors on hydrophobic surface. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116826] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Gao SR, Jin JX, Wei BJ, Zhang LZ, Yang YR, Wang XD, Lee DJ. Rebound Behaviors of Multiple Droplets Simultaneously Impacting a Superhydrophobic Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:11233-11241. [PMID: 34528810 DOI: 10.1021/acs.langmuir.1c01490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The rebound behaviors of multiple droplets simultaneously impacting a superhydrophobic surface were investigated via lattice Boltzmann method (LBM) simulations. Three rebound regions were identified, i.e., an edge-dominating region, a center-dominating region, and an independent rebound region. The occurrence of the rebound regions strongly depends on the droplet spacing and the associated Weber and Reynolds numbers. Three new rebound morphologies, i.e., a pin-shaped morphology, a downward comb-shaped morphology, and an upward comb-shaped morphology, were presented. Intriguingly, in the edge-dominating region, the central droplets experience a secondary wetting process to significantly prolong the contact time. However, in the center-dominating region, the contact time is dramatically shortened because of the strong interactions generated by the central droplets and the central ridges. These findings provide useful information for practical applications such as self-cleaning, anticorrosion, anti-icing, and so forth.
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Affiliation(s)
- Shu-Rong Gao
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Jia-Xin Jin
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Bo-Jian Wei
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Ling-Zhe Zhang
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Yan-Ru Yang
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Xiao-Dong Wang
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Duu-Jong Lee
- Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong 999077, Hong Kong, China
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Esmaeili AR, Mir N, Mohammadi R. Impact Dynamics and Freezing Behavior of Surfactant-Laden Droplets on Non-Wettable Coatings at Subzero Temperatures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:11049-11060. [PMID: 34498877 DOI: 10.1021/acs.langmuir.1c01639] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The present study investigates the impact and freezing behavior of the droplets of surfactant solutions on non-wettable coatings at very low temperatures of -10 to -30 °C. Our goal is to elucidate the critical role of concentration, molecular weight, and ionic nature of surfactants on these phenomena. To achieve this goal, we used sodium dodecyl sulfate (anionic), hexadecyltrimethylammonium bromide (cationic), and n-decanoyl-n-methylglucamine (nonionic) at four concentrations ranging from 0 to 2 × CMC (critical micelle concentration). We captured the impact-freezing of the droplets on superhydrophobic alkyl ketene dimer coatings using a high-speed camera at 5000 frames per second. The results show that the ability of the droplets to spread and retract on the coatings is a function of concentration, ionic nature, and molecular weight of the surfactants, as well as the temperature-dependent viscosity of the solutions. Additionally, surfactant-laden droplets generally demonstrated an accelerated freezing compared to pure water. This might be due to the fact that the presence of surfactants can promote both heterogeneous ice nucleation from within the liquid and a larger solid-liquid interfacial area by filling the air pockets of the surface, leading to enhanced heat transfer. The behavior of the cationic surfactant at certain concentrations was, however, an exception leading to a freezing delay, for which a mechanism will be proposed.
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Affiliation(s)
- Amir R Esmaeili
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Noshin Mir
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Reza Mohammadi
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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Yada S, Allais B, van der Wijngaart W, Lundell F, Amberg G, Bagheri S. Droplet Impact on Surfaces with Asymmetric Microscopic Features. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10849-10858. [PMID: 34469168 PMCID: PMC8447403 DOI: 10.1021/acs.langmuir.1c01813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The impact of liquid drops on a rigid surface is central in cleaning, cooling, and coating processes in both nature and industrial applications. However, it is not clear how details of pores, roughness, and texture on the solid surface influence the initial stages of the impact dynamics. Here, we experimentally study drops impacting at low velocities onto surfaces textured with asymmetric (tilted) ridges. We found that the difference between impact velocity and the capillary speed on a solid surface is a key factor of spreading asymmetry, where the capillary speed is determined by the friction at a moving three-phase contact line. The line-friction capillary number Caf = μfV0/σ (where μf,V0, and σ are the line friction, impact velocity, and surface tension, respectively) is defined as a measure of the importance of the topology of surface textures for the dynamics of droplet impact. We show that when Caf ≪ 1, the droplet impact is asymmetric; the contact line speed in the direction against the inclination of the ridges is set by line friction, whereas in the direction with inclination, the contact line is pinned at acute corners of the ridges. When Caf ≫ 1, the geometric details of nonsmooth surfaces play little role.
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Affiliation(s)
- Susumu Yada
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
| | | | | | - Fredrik Lundell
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
| | - Gustav Amberg
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
- Södertörn
University, 141 89 Stockholm, Sweden
| | - Shervin Bagheri
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
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