1
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Hu Z, Chu F, Shan H, Wu X, Dong Z, Wang R. Understanding and Utilizing Droplet Impact on Superhydrophobic Surfaces: Phenomena, Mechanisms, Regulations, Applications, and Beyond. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2310177. [PMID: 38069449 DOI: 10.1002/adma.202310177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 11/13/2023] [Indexed: 12/19/2023]
Abstract
Droplet impact is a ubiquitous liquid behavior that closely tied to human life and production, making indispensable impacts on the big world. Nature-inspired superhydrophobic surfaces provide a powerful platform for regulating droplet impact dynamics. The collision between classic phenomena of droplet impact and the advanced manufacture of superhydrophobic surfaces is lighting up the future. Accurately understanding, predicting, and tailoring droplet dynamic behaviors on superhydrophobic surfaces are progressive steps to integrate the droplet impact into versatile applications and further improve the efficiency. In this review, the progress on phenomena, mechanisms, regulations, and applications of droplet impact on superhydrophobic surfaces, bridging the gap between droplet impact, superhydrophobic surfaces, and engineering applications are comprehensively summarized. It is highlighted that droplet contact and rebound are two focal points, and their fundamentals and dynamic regulations on elaborately designed superhydrophobic surfaces are discussed in detail. For the first time, diverse applications are classified into four categories according to the requirements for droplet contact and rebound. The remaining challenges are also pointed out and future directions to trigger subsequent research on droplet impact from both scientific and applied perspectives are outlined. The review is expected to provide a general framework for understanding and utilizing droplet impact.
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Affiliation(s)
- Zhifeng Hu
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - He Shan
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xiaomin Wu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China
| | - Zhichao Dong
- CAS Key Laboratory of Bio-inspired Materials and Interfacial Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ruzhu Wang
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
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2
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Perumanath S, Chubynsky MV, Pillai R, Borg MK, Sprittles JE. Rolling and Sliding Modes of Nanodroplet Spreading: Molecular Simulations and a Continuum Approach. PHYSICAL REVIEW LETTERS 2023; 131:164001. [PMID: 37925699 DOI: 10.1103/physrevlett.131.164001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 05/11/2023] [Accepted: 08/15/2023] [Indexed: 11/07/2023]
Abstract
Molecular simulations discover a new mode of dynamic wetting that manifests itself in the very earliest stages of spreading, after a droplet contacts a solid. The observed mode is a "rolling" type of motion, characterized by a contact angle lower than the classically assumed value of 180°, and precedes the conventional "sliding" mode of spreading. This motivates the development of a novel continuum framework that captures all modes of motion, allows the dominant physical mechanisms to be understood, and permits the study of larger droplets.
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Affiliation(s)
- Sreehari Perumanath
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Mykyta V Chubynsky
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom
- Centre for Fluid and Complex Systems, Coventry University, Coventry, CV1 5FB, United Kingdom
| | - Rohit Pillai
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, United Kingdom
| | - Matthew K Borg
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, United Kingdom
| | - James E Sprittles
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom
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Tan J, Guo Y, Guo W. Diameter-Optimum Spreading for the Impinging of Water Nanodroplets on Solid Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:10504-10510. [PMID: 37462343 DOI: 10.1021/acs.langmuir.3c00983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
The impinging of water nanodroplets on solid surfaces is crucial to many nanotechnologies. Through large-scale molecular dynamics simulations, the size effect on the spreading of water nanodroplets after impinging on hydrophilic, graphite, and hydrophobic surfaces under low impinging velocities has been systematically studied. The spreading rates of nanodroplets first increase and then decrease and gradually become constant with the increase of nanodroplet diameter. The nanodroplets with the diameters of 17-19 nm possess the highest spreading rates because of the combined effect of the strongest interfacial interaction and the strongest surface interaction within water molecules. The highest water molecule densities, hydrogen bond numbers, and dielectric constants of interface and surface layers mainly contribute to the lowest interface work of adhesion and surface tension values at optimal diameters. These results unveil the nonmonotonic characteristics of spreading velocity, interface work of adhesion and surface tension with nanodroplet diameter for nanodroplets on solid surfaces.
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Affiliation(s)
- Jie Tan
- State Key Laboratory of Mechanics and Control for Aerospace Structures, MOE Key Laboratory for Intelligent Nano Materials and Devices, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Yufeng Guo
- State Key Laboratory of Mechanics and Control for Aerospace Structures, MOE Key Laboratory for Intelligent Nano Materials and Devices, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Wanlin Guo
- State Key Laboratory of Mechanics and Control for Aerospace Structures, MOE Key Laboratory for Intelligent Nano Materials and Devices, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
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Li R, Zhu P, Xu Y, Lu H, Rong J. Molecular Dynamics Simulation of Droplet Impact on a Hydrophobic 3D Elastic Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 37450274 DOI: 10.1021/acs.langmuir.3c01519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
The phenomenon of droplets impacting elastic surfaces is common in nature and in many engineering applications. It has been shown that droplet impact on an elastic surface drastically reduces droplet contact time and hinders droplet spreading. However, most of the current studies are based on experiments, and the analysis of the influence mechanism of the elastic substrate on the dynamic behavior of droplets is not complete. In addition, the simulations of droplet impact on elastic substrates are mainly focused on 2D elastic films or vibrating rigid substrates, ignoring the effect of 3D elastic substrate deformation on the droplet dynamic behavior. Therefore, in this paper, we propose to model the droplet impact on a 3D hydrophobic elastic substrate using the molecular dynamics method. We find that droplet pancake rebound can substantially reduce the droplet contact time. Moreover, we record the conditions required for the pancake rebound of the droplet. Furthermore, we investigated the effects of the elastic modulus of the substrate and the initial velocity of the droplet on the droplet contact time, contact area, and spreading factor. This study further elucidates the influence mechanism of the elastic substrate on the dynamic behavior of the droplet and provides theoretical guidance for regulating the dynamic behavior of the droplet in related fields.
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Affiliation(s)
- Rao Li
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, PR China
| | - Pengzhe Zhu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, PR China
| | - Yimeng Xu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, PR China
| | - Hongsheng Lu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, PR China
| | - Jiacheng Rong
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, PR China
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Liu H, Zhang J, Luo J, Wen D. Impact of nanodroplets on cone-textured surfaces. Phys Rev E 2023; 107:065101. [PMID: 37464703 DOI: 10.1103/physreve.107.065101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 05/10/2023] [Indexed: 07/20/2023]
Abstract
Molecular dynamics simulations have been performed to study the dynamics of nanodroplets impacting on a flat superhydrophobic surface and surfaces covered with nanocone structures. We present a panorama of nanodroplet behaviors for a wide range of impact velocities and different cone geometrics, and develop a model to predict whether a nanodroplet impacting onto cone-textured surfaces will touch the underlying substrate during impact. The advantages and disadvantages of applying nanocone structures to the solid surface are revealed by the investigations into restitution coefficient and contact time. The effects of nanocone structures on droplet bouncing dynamics are probed using momentum analysis rather than conventional energy analysis. We further demonstrate that a single Weber number is inadequate for unifying the dynamics of macroscale and nanoscale droplets on cone-textured surfaces, and propose a combined dimensionless number to address it. The extensive findings of this study carry noteworthy implications for engineering applications, such as nanoprinting and nanomedicine on functional patterned surfaces, providing fundamental support for these technologies.
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Affiliation(s)
- Hanyi Liu
- School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
| | - Jun Zhang
- School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
| | - Jia Luo
- School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
| | - Dongsheng Wen
- School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
- TUM School of Engineering and Design, Technical University of Munich, 80333 Munich, Germany
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Dynamic wetting of various liquids: Theoretical models, experiments, simulations and applications. Adv Colloid Interface Sci 2023; 313:102861. [PMID: 36842344 DOI: 10.1016/j.cis.2023.102861] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 02/12/2023] [Accepted: 02/13/2023] [Indexed: 02/23/2023]
Abstract
Dynamic wetting is a ubiquitous phenomenon and frequently observed in our daily life, as exemplified by the famous lotus effect. It is also an interfacial process of upmost importance involving many cutting-edge applications and has hence received significantly increasing academic and industrial attention for several decades. However, we are still far away to completely understand and predict wetting dynamics for a given system due to the complexity of this dynamic process. The physics of moving contact lines is mainly ascribed to the full coupling with the solid surface on which the liquids contact, the atmosphere surrounding the liquids, and the physico-chemical characteristics of the liquids involved (small-molecule liquids, metal liquids, polymer liquids, and simulated liquids). Therefore, to deepen the understanding and efficiently harness wetting dynamics, we propose to review the major advances in the available literature. After an introduction providing a concise and general background on dynamic wetting, the main theories are presented and critically compared. Next, the dynamic wetting of various liquids ranging from small-molecule liquids to simulated liquids are systematically summarized, in which the new physical concepts (such as surface segregation, contact line fluctuations, etc.) are particularly highlighted. Subsequently, the related emerging applications are briefly presented in this review. Finally, some tentative suggestions and challenges are proposed with the aim to guide future developments.
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Han N, Huang B, Sun B, He X. Oblique Impacts of Nanodroplets upon Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13093-13102. [PMID: 36268907 DOI: 10.1021/acs.langmuir.2c01797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
In this work, oblique impacts of nanodroplets impacting surfaces in a wide range of impact angles (α) are investigated in detail via molecular dynamics simulations. Five outcomes are observed, including deposition, prompt splashing, break-up, separation, and shattering. With increasing impact angle, the outcomes of prompt splashing, break-up, separation, and shattering are enlarged but the one of deposition is compressed. By drawing a Wen ∼ α phase diagram, the outcome regimes and corresponding boundaries of them can be successfully identified, and the boundary between the deposition and other outcome regimes is theoretically modeled and shows good agreement with the phase diagram, where Wen is the normal impact Weber number. For further understanding of the oblique impacts, the maximum spreading factor, as the feature parameter of spreading, is investigated. Asymmetry spreading behaviors are observed, noting that βmax,∥ is always larger than βmax,⊥. βmax,⊥ is tested that it only depends on Wen with wide impact angles and could be predicted by the scaling law of βmax,⊥ = 0.7Wen1/4. However, βmax,∥ depends on not only Wen but also impact angles. A modified model is proposed for predicting βmax,∥ as 0.7Wen1/4 + 0.001(Wen tan2 α)3/2, which shows good agreement with data on surfaces with θ from 73 to 105° in wide Wen and α ranges.
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Affiliation(s)
- Ningning Han
- Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, North China Electric Power University, Beijing102206, China
| | - Boyu Huang
- State Grid Anshan Electric Power Supply Company, Liaoning114000, China
| | - Baomin Sun
- Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, North China Electric Power University, Beijing102206, China
| | - Xin He
- School of Mechanical Engineering, Northeast Electric Power University, Jilin City132012, China
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Li R, Zhu P, Yin Z, Xu Y. Molecular Dynamics Simulation of Nanodroplets Impacting Stripe-Textured Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7058-7066. [PMID: 35608995 DOI: 10.1021/acs.langmuir.2c00770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The dynamic behavior of droplets impacting on textured surfaces has an important influence on many engineering applications, such as anti-icing and self-cleaning. However, the mechanism and law of the effect of textured surfaces on the impact behavior of nanodroplets has not been fully revealed yet. In this paper, the molecular dynamics (MD) method is used to model the dynamic behavior of nanodroplets after impacting the solid surface with a striped texture. The influences of texture gap and texture angle on the real contact area, spreading factor, contact time, and bounce velocity of the droplet after impact are also quantitatively analyzed. It is shown that the striped texture produces significant anisotropy in the spreading and contraction behavior of nanodroplets after impact, and the anisotropy is more pronounced on the ridged texture surface than on the grooved texture surface. In addition, we find that the texture gap has little effect on the dynamic behavior of nanodroplets impacting the textured surface. However, as the bottom angle of the texture increases, the real contact area and bounce velocity of the nanodroplet increase significantly, while the contact time and spreading factor decrease. This work further elucidates the characteristics and mechanisms of nanodroplets impacting on stripe-textured surfaces and provides a theoretical basis for the design of nanostructured surfaces in relevant applications.
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Affiliation(s)
- Rao Li
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, P. R. China
| | - Pengzhe Zhu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, P. R. China
| | - Zhihua Yin
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, P. R. China
| | - Yimeng Xu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing 10081, P. R. China
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A H, Yang Z, Hu R, Chen YF. Roles of energy dissipation and asymmetric wettability in spontaneous imbibition dynamics in a nanochannel. J Colloid Interface Sci 2021; 607:1023-1035. [PMID: 34571292 DOI: 10.1016/j.jcis.2021.09.051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/29/2021] [Accepted: 09/09/2021] [Indexed: 01/28/2023]
Abstract
HYPOTHESIS The imbibition dynamics is controlled by energy dissipation mechanisms and influenced by asymmetric wettability in a nanochannel. We hypothesize that the imbibition dynamics can be described by a combined model of the Lucas-Washburn equation and the Cox-Voinov law considering velocity-dependent contact angles. METHODS Molecular dynamics simulations are utilized to investigate the imbibition dynamics. A wide range of wetting conditions is achieved via adjusting the liquid-solid interaction parameters, and the spontaneous imbibition processes are quantified and compared. FINDINGS The critical condition for the occurrence of spontaneous imbibition is analyzed from a surface energy perspective. The analyses of energy conversion and dissipation indicate that the viscous dissipation is dominant during spontaneous imbibition. The classical Lucas-Washburn equation is modified with the Cox-Voinov law considering the effect of the dynamic contact angle and an effective equilibrium contact angle. We show that the proposed theory well captures the imbibition dynamics embodied in the growth of imbibition length as well as the transient interface shape and velocity for both the symmetric and asymmetric wetting conditions. In nanochannels with asymmetric wettability, the imbibition length difference between the sidewalls and interface oscillations increases with wetting disparity. Our findings deepen the understanding of imbibition dynamics on the nanoscale, and provide a theoretical reference for relevant applications.
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Affiliation(s)
- Hubao A
- State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Zhibing Yang
- State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education, Wuhan University, Wuhan 430072, China.
| | - Ran Hu
- State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Yi-Feng Chen
- State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education, Wuhan University, Wuhan 430072, China
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Yan HJ, Wan ZH, Qin FH, Sun DJ. Origin of Rebound Suppression for Dilute Polymer Solution Droplets on Superhydrophobic Substrate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:7565-7572. [PMID: 34110827 DOI: 10.1021/acs.langmuir.1c01061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Controlling droplet deposition with a minute amount of polymer additives is of profound practical importance in a wild range of applications. Previous work ascribed the relevant mechanisms to extensional viscosity, normal stress, wetting properties, etc., but the mechanism remains controversial. In this paper, we employ molecular dynamics simulations systematically for the first time to investigate the origin of rebound suppression for dilute polymer solution droplets on a flat superhydrophobic substrate. The results demonstrate that polymer-substrate interactions and impact velocities dominate the antirebound phenomenon. For low impact velocities, the dynamic characteristics of droplets are insensitive to polymer additives. However, large impact velocities will enhance the stretch behavior of polymer chains and make the chains closer to the substrate, increasing the probability of polymer molecules contacting the bottom substrate. With the cooperation of strong polymer-substrate interactions, polymer molecules can be absorbed easily by the bottom substrate, resisting the retraction process and leading to the onset of the antirebound behavior.
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Affiliation(s)
- Hong-Ji Yan
- Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Zhen-Hua Wan
- Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Feng-Hua Qin
- Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - De-Jun Sun
- Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
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Wang YB, Wang YF, Yang YR, Wang XD, Chen M. Spreading Time of Impacting Nanodroplets. J Phys Chem B 2021; 125:5630-5635. [PMID: 34008980 DOI: 10.1021/acs.jpcb.1c01735] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The kinematic time and maximum spreading time for the impact of nanodroplets of different types of fluids on solid surfaces with different wettability are investigated. It shows that the capillary regime still exits for the nanodroplet impact, even if viscous dissipation increases significantly when the droplet size reduces to the nanoscale. By taking into account the influence of liquid types and surface wettability, we first obtain scaling laws of the maximum spreading time for the capillary and viscous regimes. We further propose a universal scaling law by interpolating the scaling laws in the two asymptotic regimes. The universal scaling law is in excellent agreement with molecular dynamics simulations for various liquids and surface wettability.
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Affiliation(s)
- Yi-Bo Wang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.,Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Yi-Feng Wang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.,Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Yan-Ru Yang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.,Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Xiao-Dong Wang
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.,Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
| | - Min Chen
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
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Fan J, De Coninck J, Wu H, Wang F. A generalized examination of capillary force balance at contact line: On rough surfaces or in two-liquid systems. J Colloid Interface Sci 2020; 585:320-327. [PMID: 33302048 DOI: 10.1016/j.jcis.2020.11.100] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/24/2020] [Accepted: 11/25/2020] [Indexed: 01/01/2023]
Abstract
We investigate the capillary force balance at the contact line on rough solid surfaces and in two-liquid systems. Our results confirm that solid-liquid interactions perpendicular to the interface have a significant influence on the lateral component of the capillary force exerted on the contact line. Surface roughness of the solid substrate reduces the mobility of liquid and alters how the perpendicular solid-liquid interactions transfer into a force acting parallel to the interface. A quantitative relation between surface roughness and the transfer strategy is proposed. Moreover, when a liquid is in coexistence with another immiscible liquid on a solid, the capillary forces exerted on liquids of both sides are involved in our theoretical model. The contact angle can be predicted by calculating three interfacial tensions. These arguments are then verified by molecular dynamics simulations. Our findings set up the generalized theoretical framework for the capillary force balance at the contact line and broaden its application in more realistic scenarios.
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Affiliation(s)
- JingCun Fan
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, CAS Center for Excellence in Complex System Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Joël De Coninck
- Laboratory of Surface and Interfacial Physics (LPSI), University of Mons, 7000 Mons, Belgium
| | - HengAn Wu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, CAS Center for Excellence in Complex System Mechanics, University of Science and Technology of China, Hefei 230027, China.
| | - FengChao Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, CAS Center for Excellence in Complex System Mechanics, University of Science and Technology of China, Hefei 230027, China.
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