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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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Li Y, Zhang H, Du J, Min Q, Wu X, Sun L. Coalescence-Induced Self-Propelled Particle Transport with Asymmetry Arrangement. ACS APPLIED MATERIALS & INTERFACES 2024; 16:18184-18193. [PMID: 38556720 DOI: 10.1021/acsami.4c01355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/02/2024]
Abstract
We experimentally investigated the coalescence-induced droplet-particle jumping phenomenon on a submillimeter scale in symmetric and asymmetric particle arrangements with poly(methyl methacrylate) (PMMA) particles and stainless steel (SS) particles. Coalescence-induced droplet-particle jumping exhibited excellent capability and interesting behavior for both droplet jumping enhancement and particle transport. The particle increased the normalized droplet jumping velocity from 0.250 for no particle case to 0.315 and 0.320 for symmetric and asymmetric particle cases. Compared with similar-sized macrostructures fixed between droplets, better jumping performance with particles may be attributed to avoiding the work of adhesion during droplet-macrostructure separation. Besides, all particles always sunk at the bottom in the symmetric cases, while the stick mode for PMMA particles and sink, wander, and jet modes for SS particles appeared in the asymmetry cases. We revealed that the asymmetric particle arrangement induces an unbalanced surface tension force, which may provide a driving force in the vertical direction. Additionally, a small enough resistive force caused by hydrophobic particles is another necessary condition for the wonder and jet mode. Finally, we realized a significantly superior particle transport in the asymmetric SS particle cases with maximum particle height reaching ∼2.1 mm, ∼12.4 times the particle radius, the most significant vertical self-propelled transport distance currently.
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Affiliation(s)
- Yanzhi Li
- 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, Tsinghua University, Beijing 100084, China
| | - Haixiang Zhang
- 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, Tsinghua University, Beijing 100084, China
| | - Jiayu Du
- 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, Tsinghua University, Beijing 100084, 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, Tsinghua University, Beijing 100084, China
| | - Xinxin Wu
- 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, Tsinghua University, Beijing 100084, China
| | - Libin Sun
- 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, Tsinghua University, Beijing 100084, China
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Hou H, Wu X, Hu Z, Gao S, Yuan Z. Coalescence-Induced Droplet Jumping on Superhydrophobic Surfaces with Annular Wedge-Shaped Micropillar Arrays. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:18825-18833. [PMID: 38096374 DOI: 10.1021/acs.langmuir.3c02534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
The coalescence-induced droplet jumping on superhydrophobic surfaces has extensive application potential in water harvesting, thermal management of electronic devices, and microfluidics. The rational design of the surface structure can influence the interaction between the droplet and the surface, thereby controlling the velocity and direction of the droplet's jumping. In this study, we fabricate the superhydrophobic surface with annular wedge-shaped micropillar arrays, examine the dynamic behavior of condensate droplets on the surface, and measure the temporal and spatial variations of droplet density, average radius, and surface coverage with wedge-shaped micropillars of varying sizes. In addition, the energy analysis of the coalescence-induced droplet jumping reveals that the two primary factors influencing the jumping are the relative size and position of the droplets and micropillars. Further numerical simulations find that the wedge-shaped micropillars cause an asymmetric distribution of pressure within the droplet and at the solid-liquid contact surface, which generates an unbalanced force driving the droplet in the gradient direction of the wedge-shaped micropillar, causing the droplet to jump off the surface with both vertical and gradient-direction velocities. The capacity of the wedge-shaped micropillar surface to transport droplets in the gradient direction increases and then decreases as the relative size of the droplets and micropillars increases. The relative position of the droplet center-of-mass line perpendicular to the bottom edge of the wedge micropillars' trapezoidal shape is more favorable for droplet transport. This work reveals the influence mechanism of surface structure on the velocity and direction of droplet jumping, and the results can guide the microstructure design of superhydrophobic surfaces, which has significant implications for the application of droplet jumping.
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Affiliation(s)
- Huimin Hou
- 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
| | - Zhifeng Hu
- Research Center of Solar Power and Refrigeration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - 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
| | - Zhiping Yuan
- Department of Energy and Power Engineering, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
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Hou H, Wu X, Hu Z, Gao S, Wu Y, Lin Y, Dai L, Zou G, Liu L, Yuan Z. High-speed directional transport of condensate droplets on superhydrophobic saw-tooth surfaces. J Colloid Interface Sci 2023; 649:290-301. [PMID: 37352560 DOI: 10.1016/j.jcis.2023.06.113] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 06/12/2023] [Accepted: 06/16/2023] [Indexed: 06/25/2023]
Abstract
HYPOTHESIS Most droplets on high-efficiency condensing surfaces have radii of less than 100 μm, but conventional droplet transport methods (such as wettability-gradient surfaces and structural-curvature-gradient surfaces) that rely on the unbalanced force of three-phase lines can only transport millimeter-sized droplets efficiently. Regulating high-speed directional transport of condensate droplets is still challenging. Therefore, we present a method for condensate droplet transportation, based on the reaction force of the superhydrophobic saw-tooth surfaces to the liquid bridge, the condensate droplets could be transported at high speed and over long distances. EXPERIMENTS The superhydrophobic saw-tooth surfaces are fabricated by femtosecond laser ablation and chemical etching. Condensation experiments and luminescent particle characterization experiments on different surfaces are conducted. Aided by the theoretical analysis, we illustrate the remarkable performance of condensate droplet transportation on saw-tooth surfaces. FINDINGS Compared with conventional methods, our method improves the transport velocity and relative transport distance by 1-2 orders of magnitude and achieves directional transport of the smallest condensate droplet of about 2 μm. Furthermore, the superhydrophobic saw-tooth surfaces enable multi-hop directional jumping of condensate droplets, leading to cross-scale increases in transport distances from microns to decimeters.
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Affiliation(s)
- Huimin Hou
- 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.
| | - Zhifeng Hu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - 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
| | - Yuxi Wu
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Yukai Lin
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Liyu Dai
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Guisheng Zou
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Lei Liu
- Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Zhiping Yuan
- Department of Energy and Power Engineering, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
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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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Yang K, Liu Q, Lin Z, Liang Y, Liu C. Bouncing dynamics of impact droplets on bioinspired surfaces with mixed wettability and directional transport control. J Colloid Interface Sci 2022; 626:193-207. [DOI: 10.1016/j.jcis.2022.06.158] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 06/09/2022] [Accepted: 06/27/2022] [Indexed: 11/25/2022]
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Abstract
Large droplets emerging during dropwise condensation impair surface properties such as anti-fogging/frosting ability and heat transfer efficiency. How to spontaneously detach massive randomly distributed droplets with controlled sizes has remained a challenge. Herein, we present a solution called condensation droplet sieve, through fabricating microscale thin-walled lattice structures coated with a superhydrophobic layer. Growing droplets were observed to jump off this surface once becoming slightly larger than the lattices. The maximum radius and residual volume of droplets were strictly confined to 16 μm and 3.2 nl/mm2 respectively. We reveal that this droplet radius cut off is attributed to the large tolerance of coalescence mismatch for jumping and effective isolation of droplets between neighboring lattices. Our work brings forth a strategy for the design and fabrication of high-performance anti-dew materials. Spontaneous droplet jumping and control of dropwise condensation are relevant for water-harvesting, heat transfer and anti-frosting applications. The authors design a superhydrophobic surface with microscale thin-walled lattice structure to achieve effective jumping of droplets with specified radius range.
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Liu C, Zhao M, Lu D, Sun Y, Song L, Zheng Y. Laplace Pressure Difference Enhances Droplet Coalescence Jumping on Superhydrophobic Structures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6923-6933. [PMID: 35451848 DOI: 10.1021/acs.langmuir.2c00412] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Coalescence-induced droplet jumping has great prospects in many applications. Nevertheless, the applications are vastly limited by a low jumping velocity. Conventional methods to enhance the droplet coalescence jumping velocity are enabled by protruding structures with superhydrophobic surfaces. However, the jumping velocity improvement is limited by the height of protruding structures. Here, we present rationally designed limitation structures with superhydrophobic surfaces to achieve a dimensionless jumping velocity, Vj* ≈ 0.64. The mechanism of enhancing the jumping velocity is demonstrated through the study of numerical simulations and geometric parameters of limitation structures, providing guidelines for optimized structures. Experimental and numerical results indicate that the mechanism consists of the combined action of the velocity vectors' redirection and the Laplace pressure difference within deformed droplets trapped in limitation structures. On the basis of previous research on the mechanisms of protruding structures and our study, we successfully exploited those mechanisms to further improve the jumping velocity by combining the limitation structure with the protruding structure. Experimentally, we attained a dimensionless jumping velocity of Vj* ≈ 0.74 with an energy conversion efficiency of η ≈ 48%, breaking the jumping velocity limit. This work not only demonstrates a new mechanism for achieving a high jumping velocity and energy conversion efficiency but also sheds lights on the effect of limitation structures on coalescence hydrodynamics and elucidates a method to further enhance the jumping velocity based on protruding structures.
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Affiliation(s)
- Chuntian Liu
- 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
| | - Dunqiang Lu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Yukai Sun
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Le Song
- 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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Liu Y, Li X, Lu C, Yuan Z, Liu C, Zhang J, Zhao L. High-Efficiency Directional Ejection of Coalesced Drops on a Circular Groove. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:4028-4035. [PMID: 35319209 DOI: 10.1021/acs.langmuir.2c00023] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Coalescence-induced drop jumping has received significant attention in the past decade. However, its application remains challenging as a result of the low energy conversion efficiency and uncontrollable drop jumping direction. In this work, we report the high-efficiency coalescence-induced drop jumping with tunable jumping direction via rationally designed millimeter-sized circular grooves. By increasing the surface-droplet impact site area and restricting the oscillatory deformation, the energy conversion efficiency of the jumping droplet reaches 43.5%, 600% as high as the conventional superhydrophobic surfaces. The droplet jumping direction can be tuned from 90° to 60° by varying the principal curvature of the circular groove, while the energy conversion efficiency remains unchanged. We show through theoretical analysis and numerical simulations that the directional jumping mainly originates from reallocation of droplet momentum enabled by the asymmetric liquid bridge impact. Our study demonstrates a simple yet effective method for fast, efficient, and directional droplet removal, which warrants promising applications in jumping droplet condensation, water harvesting, anti-icing, and self-cleaning.
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Affiliation(s)
- Yahua Liu
- Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian, Liaoning 116024, People's Republic of China
- Key Laboratory of Bionic Engineering, Ministry of Education, Jilin University, Changchun, Jilin 130022, People's Republic of China
| | - Xiaojie Li
- Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian, Liaoning 116024, People's Republic of China
| | - Chenguang Lu
- Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian, Liaoning 116024, People's Republic of China
| | - Zichao Yuan
- Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian, Liaoning 116024, People's Republic of China
| | - Cong Liu
- Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian, Liaoning 116024, People's Republic of China
| | - Junqiu Zhang
- Key Laboratory of Bionic Engineering, Ministry of Education, Jilin University, Changchun, Jilin 130022, People's Republic of China
| | - Lei Zhao
- Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian, Liaoning 116024, People's Republic of China
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Liu C, Zhao M, Zheng Y, Lu D, Song L. Enhancement and Guidance of Coalescence-Induced Jumping of Droplets on Superhydrophobic Surfaces with a U-Groove. ACS APPLIED MATERIALS & INTERFACES 2021; 13:32542-32554. [PMID: 34180653 DOI: 10.1021/acsami.1c08142] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Coalescence-induced droplet jumping has received considerable attention owing to its potential to enhance performance in various applications. However, the energy conversion efficiency of droplet coalescence jumping is very low and the jumping direction is uncontrollable, which vastly limits the application of droplet coalescence jumping. In this work, we used superhydrophobic surfaces with a U-groove to experimentally achieve a high dimensionless jumping velocity Vj* ≈ 0.70, with an energy conversion efficiency η ≈ 43%, about a 900% increase in energy conversion efficiency compared to droplet coalescence jumping on flat superhydrophobic surfaces. Numerical simulation and experimental data indicated that a higher jumping velocity arises from the redirection of in-plane velocity vectors to out-of-plane velocity vectors, which is a joint effect resulting from the redirection of velocity vectors in the coalescence direction and the redirection of velocity vectors of the liquid bridge by limiting maximum deformation of the liquid bridge. Furthermore, the jumping direction of merged droplets could be easily controlled ranging from 17 to 90° by adjusting the opening direction of the U-groove, with a jumping velocity Vj* ≥ 0.70. When the opening direction is 60°, the jumping direction shows a deviation as low as 17° from the horizontal surface with a jumping velocity Vj* ≈ 0.73 and corresponding energy conversion efficiency η ≈ 46%. This work not only improves jumping velocity and energy conversion efficiency but also demonstrates the effect of the U-groove on coalescence dynamics and demonstrates a method to further control the droplet jumping direction for enhanced performance in applications.
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Affiliation(s)
- Chuntian Liu
- 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
| | - Yelong Zheng
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Dunqiang Lu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
| | - Le Song
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, People's Republic of China
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