1
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Tang S, Li Q, Li W, Chen S. Enhancement and Predictable Guidance of Coalescence-Induced Droplet Jumping on V-Shaped Superhydrophobic Surfaces with a Ridge. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 39133052 DOI: 10.1021/acs.langmuir.4c01809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/13/2024]
Abstract
Coalescence-induced droplet jumping has attracted significant attention in recent years. However, achieving a high jumping velocity while predictably regulating the jumping direction of the merged droplets by simple superhydrophobic structures remains a challenge. In this work, a novel V-shaped superhydrophobic surface with a ridge is conceived for enhanced and predictably guided coalescence-induced droplet jumping. By conducting experiments and lattice Boltzmann simulations, it is found that the presence of a ridge in the V-shaped superhydrophobic surface can modify the fluid dynamics during the droplet coalescence process, resulting in a much higher droplet jumping velocity than that achieved by the V-shaped superhydrophobic surface without a ridge. The enhancement of the droplet jumping velocity is mainly attributed to the combined effect of the earlier and more sufficient impingement between the liquid bridge and the ridge, as well as the accelerated droplet contraction by redirecting the internal liquid flow toward the jumping direction. A high normalized jumping velocity of V j * ≈ 0.71 is achieved by the newly designed surface, with a 930% increase in the energy conversion efficiency in comparison with that on a flat surface. Moreover, adjusting the opening direction of the V-groove at different groove angles is found to be an effective method to regulate the droplet jumping direction and expand the range of the jumping angle. Particularly, the droplet jumping angle can be well predicted based on the rotational angle (ω) and the groove angle (α), i.e., θj,p ≈ 90° - 0.5α - ω.
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Affiliation(s)
- Shi Tang
- School of Energy Science and Engineering, Central South University, Changsha 410083, China
| | - Qing Li
- School of Energy Science and Engineering, Central South University, Changsha 410083, China
| | - Wanxin Li
- School of Energy Science and Engineering, Central South University, Changsha 410083, China
| | - Shoutian Chen
- School of Energy Science and Engineering, Central South University, Changsha 410083, China
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2
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Challita EJ, Rohilla P, Bhamla MS. Fluid Ejections in Nature. Annu Rev Chem Biomol Eng 2024; 15:187-217. [PMID: 38669514 PMCID: PMC11269045 DOI: 10.1146/annurev-chembioeng-100722-113148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024]
Abstract
From microscopic fungi to colossal whales, fluid ejections are universal and intricate phenomena in biology, serving vital functions such as animal excretion, venom spraying, prey hunting, spore dispersal, and plant guttation. This review delves into the complex fluid physics of ejections across various scales, exploring both muscle-powered active systems and passive mechanisms driven by gravity or osmosis. It introduces a framework using dimensionless numbers to delineate transitions from dripping to jetting and elucidate the governing forces. Highlighting the understudied area of complex fluid ejections, this review not only rationalizes the biophysics involved but also uncovers potential engineering applications in soft robotics, additive manufacturing, and drug delivery. By bridging biomechanics, the physics of living systems, and fluid dynamics, this review offers valuable insights into the diverse world of fluid ejections and paves the way for future bioinspired research across the spectrum of life.
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Affiliation(s)
- Elio J Challita
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA;
| | - Pankaj Rohilla
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA;
| | - M Saad Bhamla
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA;
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3
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Meng Y, Zhou Y, Wang X, Wei W, Hu Y, Chen B, Zhong D. Direct Nanosecond Multiframe Imaging of Irreversible Dynamics in 4D Electron Microscopy. NANO LETTERS 2024. [PMID: 38856109 DOI: 10.1021/acs.nanolett.4c01025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Irreversible ultrafast events are prevalent in nature, yet their capture in real time poses significant challenges. Traditional single-shot imaging technologies, which utilize a single optical pump and single delayed electron probe, offer high spatiotemporal resolution but fail to capture the entire dynamic evolutions. Here, we introduce a novel imaging method employing a single optical pump and delayed multiple electron probes. This approach, facilitated by an innovative deflector in ultrafast electron microscopy, enables the acquisition of nine frames per exposure, paving the way for statistical and quantitative analyses. We have developed an algorithm that corrects frame-by-frame distortions, realizing a cross-correlation enhancement of ∼26%. Achieving ∼12 nm and 20 ns resolution, our method allows for the comprehensive visualization of laser-induced behaviors in Au nanoparticles, including merging, jumping, and collision processes. Our results demonstrate the capability of this multiframe imaging technique to document irreversible processes across materials science and biology with unprecedented nanometer-nanosecond precision.
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Affiliation(s)
- Yenan Meng
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, and School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yu Zhou
- State Key Laboratory of Mechanical System and Vibration School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiaoxiang Wang
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, and School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Weiyu Wei
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, and School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yongxiang Hu
- State Key Laboratory of Mechanical System and Vibration School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Bin Chen
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, and School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dongping Zhong
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, and School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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4
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Chu J, Feng X, Li Y, Li F, Tian G. Hierarchical Structure with Microcrater Covered with Nanograss Enhancing Condensation and Its Antifrosting/Anti-Icing Performance Inspired by Euphorbia helioscopia L. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:10313-10325. [PMID: 38683169 DOI: 10.1021/acs.langmuir.4c00934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Abstract
Over an extended period of evolution and natural selection, a multitude of species developed a diverse array of biological interface features with specific functions. These biological structures provide a rich source of inspiration for the design of bionic structures on superhydrophobic surfaces. Understanding the functional mechanism of plant leaves is of paramount importance for the advancement of new engineering materials and the further promotion of engineering applications of bionic research. The hierarchical structure of microcrater-covered nanograss (MCNG) on the surface of E. helioscopia L. leaf provided the inspiration for the bionic MCNG surface, which was successfully prepared on a copper substrate by hybrid laser micromachining technology and chemical etching. The combined action of texture structure and surface chemistry resulted in a contact angle of 169° ± 1° for MCNG surface droplets and a rolling angle of less than 1°. Notably, the condensation-induced adhesion force does not augment with the increase of the temperature difference, which facilitated the shedding of hot droplets from the surface. The microscope observation revealed a high density of condensed droplets on the MCNG surface and the tangible jumping behavior of the droplets. The fabricated MCNG also demonstrated excellent antifrost/anti-icing abilities in low-temperature and high-humidity environments. Finally, the study confirmed the exceptional mechanical durability and reusability of the MCNG surface through various tests, including scratch damage, sandpaper wear, water flow impact and flushing, and condensation-drying cycle tests. The nanograss can be effectively protected within the microcrater structure. This research presents a promising approach for preventing and/or removing unwanted droplets in numerous engineering applications.
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Affiliation(s)
- Jiahui Chu
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Xiaoming Feng
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Yan Li
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Fengqin Li
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
| | - Guizhong Tian
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
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5
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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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6
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Wang DQ, Wang ZJ, Wang SY, Yang YR, Zheng SF, Lee DJ, Wang XD. Coalescence-Induced Jumping of Nanodroplets in a Perpendicular Electric Field: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 38298055 DOI: 10.1021/acs.langmuir.3c03758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
Coalescence-induced jumping has promised a substantial reduction in the droplet detachment size and consequently shows great potential for heat-transfer enhancement in dropwise condensation. In this work, using molecular dynamics simulations, the evolution dynamics of the liquid bridge and the jumping velocity during coalescence-induced nanodroplet jumping under a perpendicular electric field are studied for the first time to further promote jumping. It is found that using a constant electric field, the jumping performance at the small intensity is weakened owing to the continuously decreased interfacial tension. There is a critical intensity above which the electric field can considerably enhance the stretching effect with a stronger liquid-bridge impact and, hence, improve the jumping performance. For canceling the inhibition effect of the interfacial tension under the condition of the weak electric field, a square-pulsed electric field with a paused electrical effect at the expansion stage of the liquid bridge is proposed and presents an efficient nanodroplet jumping even using the weak electric field.
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Affiliation(s)
- Dan-Qi 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
| | - Zi-Jie 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
| | - Shao-Yu 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
| | - Shao-Fei Zheng
- 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
| | - Duu-Jong Lee
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong 999077, Hong Kong
- Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li 32003, Taiwan
| | - 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
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7
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Ma C, Wang L, Xu Z, Tong W, Zheng Q. Uniform and Persistent Jumping Detachment of Condensed Nanodroplets. NANO LETTERS 2024; 24:1439-1446. [PMID: 38237068 DOI: 10.1021/acs.nanolett.3c04930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
Realizing jumping detachment of condensed droplets from solid surfaces at the smallest sizes possible is vital for applications such as antifogging/frosting and heat transfer. For instance, if droplets uniformly jump at sizes smaller than visible light wavelengths of 400-720 nm, antifogging issues could be resolved. In comparison, the smallest droplets experimentally observed so far to jump uniformly were around 16 μm in radius. Here, we show molecular dynamics (MD) simulations of persistent droplet jumping with a uniform radius down to only 3.6 nm on superhydrophobic thin-walled lattice (TWL) nanostructures integrated with superhydrophilic nanospots. The size cutoff is attributed to the preferential cross-lattice coalescence of island droplets. As an application, the MD results exhibit a 10× boost in the heat transfer coefficient (HTC), showing a -1 scaling law with the maximum droplet radius. We provide phase diagrams for jumping and wetting behaviors to guide the design of lattice structures with advanced antidew performance.
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Affiliation(s)
- Chen Ma
- Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, China
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
| | - Lin Wang
- Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, China
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University, Jinan 250100, China
| | - Zhi Xu
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Tribology in Advanced Equipment (SKLT), Tsinghua University, Beijing 100084, China
| | - Wei Tong
- Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, China
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
- Institute of Superlubricity Technology, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China
| | - Quanshui Zheng
- Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, China
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Tribology in Advanced Equipment (SKLT), Tsinghua University, Beijing 100084, China
- Institute of Superlubricity Technology, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China
- Institute of Materials Research, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518057, China
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8
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Cong Q, Qin X, Chen T, Jin J, Liu C, Wang M. Research Progress of Superhydrophobic Materials in the Field of Anti-/De-Icing and Their Preparation: A Review. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5151. [PMID: 37512424 PMCID: PMC10386049 DOI: 10.3390/ma16145151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 06/09/2023] [Accepted: 06/22/2023] [Indexed: 07/30/2023]
Abstract
Accumulated ice has brought much damage to engineering and people's lives. The accumulation of ice can affect the flight safety of aircraft and lead to the failure of cables and power generation blades; it can even cause damage to human life. Traditional anti-icing and de-icing strategies have many disadvantages such as high energy consumption, low efficiency, or pollution of the environment. Therefore, inspired by animal communities, researchers have developed new passive anti-icing materials such as superhydrophobic material. In this paper, the solid surface wetting phenomenon and superhydrophobic anti-icing and de-icing mechanism were introduced. The methods of fabrication of superhydrophobic surfaces were summarized. The research progress of wear-resistant superhydrophobic coatings, self-healing/self-repairing superhydrophobic coatings, photothermal superhydrophobic coatings, and electrothermal superhydrophobic coatings in the field of anti-icing and de-icing was reviewed. The current problems and challenges were analyzed, and the development trend of superhydrophobic materials was also prospected in the field of anti-icing and de-icing. The practicality of current superhydrophobic materials should continue to be explored in depth.
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Affiliation(s)
- Qian Cong
- Key Laboratory of Bionic Engineering (Ministry of Education), College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Xiuzhang Qin
- Key Laboratory of Bionic Engineering (Ministry of Education), College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Tingkun Chen
- Key Laboratory of Bionic Engineering (Ministry of Education), College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Jingfu Jin
- Key Laboratory of Bionic Engineering (Ministry of Education), College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Chaozong Liu
- Department of Ortho and MSK Science, University College London, London HA7 4LP, UK
| | - Mingqing Wang
- Institute for Materials Discovery, University College London, London WC1E 7JE, UK
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9
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Li B, Tan W, Liu G, Huang M. Dynamics of Droplet Coalescence on Hydrophobic Fibers in Oil: Morphology and Liquid Bridge Evolution. ACS OMEGA 2023; 8:18019-18028. [PMID: 37251168 PMCID: PMC10210508 DOI: 10.1021/acsomega.3c01209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 05/03/2023] [Indexed: 05/31/2023]
Abstract
Although droplet self-jumping on hydrophobic fibers is a well-known phenomenon, the influence of viscous bulk fluids on this process is still not fully understood. In this work, two water droplets' coalescence on a single stainless-steel fiber in oil was investigated experimentally. Results showed that lowering the bulk fluid viscosity and increasing the oil-water interfacial tension promoted droplet deformation, reducing the coalescence time of each stage. While the total coalescence time was more influenced by the viscosity and under-oil contact angle than the bulk fluid density. For water droplets coalescing on hydrophobic fibers in oils, the expansion of the liquid bridge can be affected by the bulk fluid, but the expansion dynamics exhibited similar behavior. The drops begin their coalescence in an inertially limited viscous regime and transition to an inertia regime. Larger droplets did accelerate the expansion of the liquid bridge but had no obvious influence on the number of coalescence stages and coalescence time. This study can provide a more profound understanding of the mechanisms underlying the behavior of water droplet coalescence on hydrophobic surfaces in oil.
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Affiliation(s)
- Bingbing Li
- School
of Energy and Chemical Engineering, Tianjin
Renai College, Boxueyuan,
Tuanbo New Town, Jinghai District, Tianjin 301636, P. R. China
| | - Wei Tan
- School
of Chemical Engineering and Technology, Tianjin University, No. 135 Yaguan Road, Haihe Education Park, Tianjin 300354, P. R. China
| | - Guiyu Liu
- School
of Energy and Chemical Engineering, Tianjin
Renai College, Boxueyuan,
Tuanbo New Town, Jinghai District, Tianjin 301636, P. R. China
| | - Mo Huang
- Audit
Department, Jiangxi University of Chinese
Medicine, 1688 Meiling
Dadao, Xinjian District, Nanchang City, Jiangxi Province 330004, P. R. China
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10
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Qiu L, Qian S, Ni Y, Tong Q. Optimum substrate stiffness in coalescence-induced droplet jumping. Phys Chem Chem Phys 2023; 25:14368-14373. [PMID: 37183923 DOI: 10.1039/d3cp00835e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
When droplets are brought into contact and coalesced on a superhydrophobic surface, the kinetic energy converted from the surface energy enables the merged droplet to jump. Current studies mainly focus on the microstructure of surfaces and the properties of droplets that influence the jumping dynamics. Here, by means of molecular dynamics, we investigate the coalescence-induced jumping of nanodroplets on soft substrates. The optimum stiffness of the substrate is suggested and the mechanism involved is demonstrated through the analysis of the interactions between the droplets and the substrates. The momentum of the droplet is evaluated by integrating the forces from the substrate. The optimum stiffness for jumping velocity is provided by the competition between the impact and the adhesion from the substrate during the process, which are both closely related to the stiffness. The results may inspire fundamental research and applications in a broad scope.
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Affiliation(s)
- Lianfu Qiu
- Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China.
| | - Sheng Qian
- Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China.
| | - Yifeng Ni
- Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China.
- Shanghai Minghua Electric Power Science & Technology Co., Ltd., Shanghai 200090, China
| | - Qi Tong
- Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China.
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11
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Thomas T, Sinha Mahapatra P, Ganguly R, Tiwari MK. Preferred Mode of Atmospheric Water Vapor Condensation on Nanoengineered Surfaces: Dropwise or Filmwise? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5396-5407. [PMID: 37014297 PMCID: PMC10116598 DOI: 10.1021/acs.langmuir.3c00022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 03/22/2023] [Indexed: 06/19/2023]
Abstract
Condensing atmospheric water vapor on surfaces is a sustainable approach to addressing the potable water crisis. However, despite extensive research, a key question remains: what is the optimal combination of the mode and mechanism of condensation as well as the surface wettability for the best possible water harvesting efficacy? Here, we show how various modes of condensation fare differently in a humid air environment. During condensation from humid air, it is important to note that the thermal resistance across the condensate is nondominant, and the energy transfer is controlled by vapor diffusion across the boundary layer and condensate drainage from the condenser surface. This implies that, unlike condensation from pure steam, filmwise condensation from humid air would exhibit the highest water collection efficiency on superhydrophilic surfaces. To demonstrate this, we measured the condensation rates on different sets of superhydrophilic and superhydrophobic surfaces that were cooled below the dew points using a Peltier cooler. Experiments were performed over a wide range of degrees of subcooling (10-26 °C) and humidity-ratio differences (5-45 g/kg of dry air). Depending upon the thermodynamic parameters, the condensation rate is found to be 57-333% higher on the superhydrophilic surfaces compared to the superhydrophobic ones. The findings of the study dispel ambiguity about the preferred mode of vapor condensation from humid air on wettability-engineered surfaces and lead to the design of efficient atmospheric water harvesting systems.
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Affiliation(s)
- Tibin
M. Thomas
- Department
of Mechanical Engineering, Indian Institute
of Technology Madras, Chennai 600036, India
| | - Pallab Sinha Mahapatra
- Department
of Mechanical Engineering, Indian Institute
of Technology Madras, Chennai 600036, India
| | - Ranjan Ganguly
- Department
of Power Engineering, Jadavpur University, Kolkata 700106, India
| | - Manish K. Tiwari
- Nanoengineered
Systems Laboratory, UCL, London WC1E 7JE, U.K.
- Wellcome/EPSRC
Centre for Interventional and Surgical Sciences, UCL, London W1W 7TS, U.K.
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12
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Coalescence-induced jumping of in-plane moving droplets: Effects of initial velocity and sideslip angle. Chem Eng Sci 2023. [DOI: 10.1016/j.ces.2022.118247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Li Y, Du J, Wu X, Lu G, Min Q. How macrostructures enhance droplet coalescence jumping: A mechanism study. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.130740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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14
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Gao S, Wu X. Numerical Investigation on Coalescence-Induced Jumping of Centripetal Moving Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:12674-12681. [PMID: 36201740 DOI: 10.1021/acs.langmuir.2c02160] [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
Coalescence-induced droplet jumping could promote self-removal of droplets, which has broad potential in related fields such as heat-transfer enhancement, self-cleaning, energy harvesting, electricity generation, radiative cooling, and antifrosting/icing. In practical applications, droplets often have initial velocity under external forces. In this work, the coalescence-induced jumping of centripetal moving droplets on a superhydrophobic plane is experimentally observed using a high-speed photography platform, and the effects of the initial velocity of the moving droplet on jumping velocity, energy conversion, and droplet morphology are numerically investigated. Results show that the jumping velocity decreases and then increases as the We number of the moving droplet increases. The main source of the total kinetic energy of the coalesced droplet switches from the released surface energy to the initial kinetic energy of the moving droplet with the increasing We number, but the proportion of the jumping kinetic energy to the total kinetic energy decreases. Besides, the initial velocity of the moving droplet intensifies the droplet deformation and accelerates the process of coalescence-induced jumping. Through theoretical analysis, it is found that the jumping velocity is affected by two mechanisms: the deformation intensification and the liquid bridge impact enhancement.
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Affiliation(s)
- Sihang Gao
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, 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
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15
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Li T. Coalescence-Induced Jumping for Removing the Deposited Heterogeneous Droplets: A Molecular Dynamics Simulation Study. J Phys Chem B 2022; 126:8030-8038. [PMID: 36174232 DOI: 10.1021/acs.jpcb.2c05570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The removal of the deposited droplets on a solid surface is crucial to considerable practical applications that require self-cleaning properties. In this work, a strategy of cleaning a deposited droplet ("D-droplet") by coalescing with a heterogeneous and easily jumping droplet ("J-droplet") is proposed. Molecular dynamics simulation studies have shown that the coalescence of these two kinds of droplets would not guarantee the removal of D-droplet, unless the lifting ability of J-droplet is enhanced through the reduction of the solid-liquid interaction. However, this is a bad scenario with low efficiency. Further investigation suggests that by introducing two J-droplets to produce triple-coalescence dynamics, the D-droplet could be successfully jumping from the substrates due to the coalescence-induced effect, which is also verified by the free energy calculation. Moreover, the effects of the size of the droplets and the arrangement mode of these three droplets on the jumping dynamics are both considered. The studies not only help advance our understanding of coalescence-induced jumping of heterogeneous droplets, but also open up new ways to remove the deposited impure droplets, which is expected to guide the fields of self-cleaning.
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Affiliation(s)
- Tao Li
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong999077, China
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Jiang S, Diao Y, Yang H. Recent advances of bio-inspired anti-icing surfaces. Adv Colloid Interface Sci 2022; 308:102756. [PMID: 36007284 DOI: 10.1016/j.cis.2022.102756] [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: 05/12/2022] [Revised: 07/16/2022] [Accepted: 08/11/2022] [Indexed: 11/25/2022]
Abstract
The need for improved anti-icing surfaces is the demand of the time and closely related to many important aspects of our lives as surface icing threatens not only industrial production but also human safety. Freezing on a cold surface is usually a heterogeneous nucleation process induced by the substrate. Creating an anti-icing surface is mainly achieved by changing surface morphology and chemistry to regulate the interaction between the surface and the water/ice to inhibit freezing on the surface. In this paper, recent research progress in the creation of biomimetic anti-icing surfaces is reviewed. Firstly, basic strategies of bionic anti-icing are introduced, and then bionic anti-icing surface strategies are reviewed according to four aspects: the process of ice formation, including condensate self-removing, inhibiting ice nucleation, reducing ice adhesion, and melting accumulated ice on the surface. The remaining challenges and the direction of future development of biomimetic anti-icing surfaces are also discussed.
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Affiliation(s)
- Shanshan Jiang
- School of Materials Science and Engineering, Zhengzhou University, 450001 Zhengzhou, Henan, China
| | - Yunhe Diao
- School of Materials Science and Engineering, Zhengzhou University, 450001 Zhengzhou, Henan, China
| | - Huige Yang
- School of Materials Science and Engineering, Zhengzhou University, 450001 Zhengzhou, Henan, China.
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Oscillatory Signatures in the Raindrop Motion Relative to the Air Medium with Terminal Velocity. ATMOSPHERE 2022. [DOI: 10.3390/atmos13071137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This paper aims to study the path oscillations of single, spherical water droplets levitated in a wind tunnel to better comprehend the mechanical motion of small raindrops. The observations were carried out in the Mainz vertical wind tunnel. The discrete, fast Fourier transform was used to determine the oscillatory frequencies of the droplet paths, and the Hilbert transform was applied to analyze their instantaneous frequency stability. Both transversal and streamwise components of the path oscillations are described with typical frequencies of several tens of Hertz. The studied oscillations elongate the paths, reduce the terminal velocity of the smallest droplets, and make the rain droplet fall in a non-uniform motion even after reaching terminal velocity. The terminal velocity can be considered as physically having been reached if our proposed practical criterion is satisfied. From a fluid mechanics perspective, the paper fills an experimental gap in the studies of the paths oscillations of single, liquid spheres of microscopic sizes at low Bond numbers <1 and relatively low Reynolds numbers ~102.
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