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Liu Z, Luo Y, Chen L, Yang Y, Lyu S, Luo Z. The Droplet Creeping-Sliding Dynamic Wetting Mechanism on Bionic Self-Cleaning Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:12602-12612. [PMID: 38848496 DOI: 10.1021/acs.langmuir.4c01063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2024]
Abstract
The dynamic wetting behavior of droplets has been of wide concern due to the hazards of accretion/icing of supercooled droplets on engineering components/systems served in low temperature freezing rain environment; thus, it is urgent to establish the relationship between droplet depinning/removing behaviors and surface characteristics. In this article, the actual rotation conditions of moving components such as wind turbine blades are simulated. The self-cleaning hydrophobic coating surface(S1) and bionic superhydrophobic coating surface(S2) show outstanding droplet removal performance compared to hydrophilic bare steel surface(S0), and the average speed of the droplet removal is increased by 400-500%. The "creeping-sliding" behavior of droplets on self-cleaning coatings is investigated by the change of droplet displacement(ΔD). The effect of the energy storage caused by the droplet creeping process provides initial kinetic energy for the droplet removal. Combined with the experimental data and theoretical model, the critical depinning resistance is calculated. The difference of the wetting interface free energy(ΔEx) during the dynamic wetting process of the droplets on the bionic superhydrophobic self-cleaning surface is researched. And the influence mechanism of the droplet embedded depth(x) on the creeping/sliding behavior in the nanotexture is clarified. Thus, the mechanical criterion of droplet depinning is proposed (the error is about 10%). The results can provide a theoretical basis for the design principle of antifreezing rain coatings on moving components.
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Affiliation(s)
- Zexuan Liu
- School of Materials, Sun Yat-Sen University, Shenzhen 518107, P. R. China
| | - Yimin Luo
- School of Materials, Sun Yat-Sen University, Shenzhen 518107, P. R. China
- State Key Laboratory of Solid Lubrication, Lanzhou Insti-tute of Chemical Physics, Chinese Academy of Sciences, Gansu Lanzhou 730000, P. R. China
| | - Litao Chen
- School of Materials, Sun Yat-Sen University, Shenzhen 518107, P. R. China
| | - Yujie Yang
- School of Materials, Sun Yat-Sen University, Shenzhen 518107, P. R. China
| | - Shushen Lyu
- School of Materials, Sun Yat-Sen University, Shenzhen 518107, P. R. China
| | - Zhuangzhu Luo
- School of Materials, Sun Yat-Sen University, Shenzhen 518107, P. R. China
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Wang X, Zeng Y, Yuan Z, Chen F, Lo WK, Yuan Y, Li T, Yan X, Wang S. Forced capillary wetting of viscoelastic fluids. J Colloid Interface Sci 2024; 662:555-562. [PMID: 38367573 DOI: 10.1016/j.jcis.2024.02.078] [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: 11/17/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/19/2024]
Abstract
HYPOTHESIS Achieving rapid capillary wetting is highly desirable in nature and industries. Previous endeavors have primarily concentrated on passive wetting strategies through surface engineering. However, these approaches are inadequate for high-viscosity fluids due to the significant viscous resistance, especially for non-Newtonian fluids. In contrast, forced wetting emerges as a promising method to address the challenges associated with achieving rapid wetting of non-Newtonian fluids in capillaries. EXPERIMENTS To investigate the forced wetting behavior of viscoelastic fluids in capillaries, we employ Xanthan Gum (XG) aqueous solutions as target fluids with the storage modulus significantly exceeding the loss modulus. We utilize smooth glass capillaries connected to a syringe pump to achieve high moving speeds of up to 1 m/s. FINDINGS Our experiments reveal a significant distinction in the power-law exponent that governs the scaling relationship between the dynamic contact angle and velocity for viscoelastic fluids compared to Newtonian fluids. This exponent is considerably smaller and varies based on the concentration of viscoelastic fluids and the diameter of the capillaries. We suggest that the viscosity dominates the wetting dynamics of viscoelastic fluids, manifested by the contact line morphology-dependent behavior. This insight has significant implications for microfluidics and drug injectability.
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Affiliation(s)
- Xiong Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China; Centre for Nature-Inspired Engineering, City University of Hong Kong, Hong Kong, China.
| | - Yijun Zeng
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
| | - Zhenyue Yuan
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
| | - Feipeng Chen
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Wai Kin Lo
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China; Centre for Nature-Inspired Engineering, City University of Hong Kong, Hong Kong, China
| | - Yongjiu Yuan
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China; Centre for Nature-Inspired Engineering, City University of Hong Kong, Hong Kong, China
| | - Tong Li
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China; Centre for Nature-Inspired Engineering, City University of Hong Kong, Hong Kong, China
| | - Xiao Yan
- School of Energy and Power Engineering, Chongqing University, Chongqing, China
| | - Steven Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China; Centre for Nature-Inspired Engineering, City University of Hong Kong, Hong Kong, China.
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Wang JX, Qian J, Li JX, Wang X, Lei C, Li S, Li J, Zhong M, Mao Y. Enhanced interfacial boiling of impacting droplets upon vibratory surfaces. J Colloid Interface Sci 2024; 658:748-757. [PMID: 38142625 DOI: 10.1016/j.jcis.2023.12.095] [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: 09/25/2023] [Revised: 12/02/2023] [Accepted: 12/14/2023] [Indexed: 12/26/2023]
Abstract
HYPOTHESIS Despite the flourishing studies of droplet interfacial boiling, the boiling upon vibratory surfaces, which may cause vigorous liquid-vapor-solid interactions, has rarely been investigated. Enhanced boiling normally can be gained from rapid removal of vapor and disturbance of liquid-vapor interface. We hypothesize that the vibratory surfaces enhance both effects with new intriguing phenomena and thus, attain an enhanced boiling heat transfer. EXPERIMENTS We experimentally investigated the impacting fluid dynamics and coupled heat transfer patterns of multiple droplets and a single droplet impinging on still and vibratory surfaces of various materials and different wettability. FINDINGS The boiling under vibratory surfaces with increased vibration velocity amplitude and enhanced wettability can be enhanced by 80% in heat transfer coefficient and Nusselt number, which is attributed to several reasons: shortened bubble lifespan, thinner and smaller bubbles, and enhanced disturbances in liquid-vapor interfaces. The vibration also delays the Leidenfrost point when the droplet impacts a descending surface, which shows that the droplet impact moment (vibration phase angle) is particularly crucial. The descending surface releases the generated vapor actively and facilitates liquid-solid contact, thereby delaying the Leidenfrost. From fundamentals to application, this article strengthens our understanding of vibrated interfacial boiling in scenarios closer to multiple natural processes and practical industries.
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Affiliation(s)
- Ji-Xiang Wang
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China; Hebei Key Laboratory of Man-machine Environmental Thermal Control Technology and Equipment, Hebei Vocational University of Technology and Engineering, Hebei 054000, PR China; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, PR China; Taizhou Wavexploration Energy Ltd., Taizhou, 225513, PR China
| | - Jian Qian
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China
| | - Jia-Xin Li
- China Academy of Launch Vehicle Technology, Beijing 100076, PR China
| | - Xiong Wang
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, PR China
| | - Chaojie Lei
- Beijing Sino-Spark Technology Co., Ltd., Beijing 100191, PR China
| | - Shengquan Li
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China
| | - Jun Li
- School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, PR China.
| | - Mingliang Zhong
- Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, PR China; National Key Laboratory of Optical Field Manipulation Science and Technology, Chinese Academy of Sciences, Chengdu 610209, PR China.
| | - Yufeng Mao
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China; Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, PR China; National Key Laboratory of Optical Field Manipulation Science and Technology, Chinese Academy of Sciences, Chengdu 610209, PR China.
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Wang X, Yan X, Min Q. Mass transfer of microbubble in liquid under multifrequency acoustic excitation - A theoretical study. ULTRASONICS SONOCHEMISTRY 2024; 102:106760. [PMID: 38199078 PMCID: PMC10788794 DOI: 10.1016/j.ultsonch.2024.106760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 12/05/2023] [Accepted: 01/05/2024] [Indexed: 01/12/2024]
Abstract
Microbubble's mass transfer under external acoustic excitation holds immense potential across various technological fields. However, the current state of acoustic technology faces limitations due to inadequate control over bubble size in liquids under external excitation. Here, we conducted numerical investigations of the mass transfer behavior of microbubbles in liquids under multifrequency acoustic excitations with different frequencies (in the MHz range), pressure amplitudes (in the range of several atmospheric pressures), and amplitude ratios. We identified various pressure threshold regions for the growth of gas bubbles (radii range from a few microns to tens of microns) and observed common intersections between single and multifrequency excitations that enable effective control of the growth intervals and final size of bubbles by adjusting the ratio of pressure amplitude and frequency value. Allocating power to the lower frequency component of multifrequency acoustic excitation is recommended to facilitate mass transfer or diffusion, as small-frequency acoustic excitation has a more significant effect than the higher frequency in the growth region. Our study provides a better understanding of the dynamics of bubbles under complex excitations and has practical implications for developing methods to control and promote bubble-related processes.
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Affiliation(s)
- Xiong Wang
- Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Institute of Nuclear and New Energy Technology, Beijing 100084, China; Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077, China.
| | - Xiao Yan
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 400030, China; Institute of Engineering Thermophysics, Chongqing University, Chongqing 400030, China
| | - Qi Min
- Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Institute of Nuclear and New Energy Technology, Beijing 100084, China.
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Yin Y, Zhao L, Lin S. CO 2-philicity to CO 2-phobicity Transition on Smooth and Stochastic Rough Cu-like Substrate Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 38039439 DOI: 10.1021/acs.langmuir.3c02434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2023]
Abstract
CO2 on metal substrates is essential to CO2 liquefaction and transportation of CO2, yet the manipulation of the wettability of the CO2 and the elucidation of its underlying mechanism have not been fully achieved. Here, using molecular dynamics simulations, we report CO2 wetting characteristics on both smooth and stochastic rough Cu-like substrate surfaces. The results indicate that the apparent contact angle (CA) of the CO2 droplet on the smooth surface decreases from 180° to 0° as the CO2-solid characteristic interaction energy increases from 0.002 to 0.016 eV. In addition, the CAs become greater with increasing the density of surface asperities, regardless of the intrinsic surface wettability. This is attributed to the capillary drying-out of liquid CO2 molecules in gaps between surface asperities at the three-phase contact line of the droplet, which is usually overlooked in previous theoretical studies. Notably, the intrinsically CO2-philic surface transforms to the CO2-phobic due to an increase in the density of surface rugosity. Moreover, we verify the range of applicability of the CA prediction models concerning the nanoscale asperities. This work is beneficial for fully understanding the influence of nanoscale surface topography on CO2 wettability and shedding light on the design of functionalized and patterned surfaces to manipulate CO2 wettability.
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Affiliation(s)
- Yuming Yin
- National Engineering Research Center of Turbo-Generator Vibration, School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China
| | - Lingling Zhao
- National Engineering Research Center of Turbo-Generator Vibration, School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China
| | - Shangchao Lin
- Institute of Engineering Thermophysics, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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