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Li H, Zhang Q, Chen L, Wang Y, Ai Z, Zhang T, Liu F, Zhong F. Preparation of hyaluronic acid-loaded liquid-core hydrogel beads with acceptable mechanical properties and thermal stability. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2024; 104:5834-5845. [PMID: 38380967 DOI: 10.1002/jsfa.13406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/19/2024] [Accepted: 02/19/2024] [Indexed: 02/22/2024]
Abstract
BACKGROUND Hyaluronic acid liquid-core hydrogel beads (HA-LHB) is a good way for oral intake of HA. However, HA may affect the reaction-diffusion of sodium alginate (SA) and Ca2+ leading to poor mechanical properties, since HA is a polyanionic electrolyte having electrostatic effect and a certain spatial site-blocking effect. RESULTS The mechanical properties of HA-LHB were modified from bathing solution, core solution and secondary calcium bath time. The mechanical properties varied with the SA structure and concentration in bathing solution, where SA with high G (guluronic acid) segment compounded with SA with high M (mannuronic acid) segment at a mass ratio of 7:3 with a 11 g kg-1 concentration showed the best mechanical properties. The secondary calcium bath can greatly improve the mechanical properties due to the tight network formed by bidirectional crosslinking, and 15 min reaction reached the plateau if Ca2+ is sufficient. And the mechanical properties were positively correlated with calcium lactate concentration only at <70 g kg-1 in core solution, but the diffusion of Ca2+ was hindered by the tight gel network at higher concentrations. Moreover, the mechanical properties can be maintained during heat treatment, due to the rearrangement of alginate network structure. CONCLUSION Our results suggested that the problem of poor mechanical properties of LHB in the presence of high HA concentration can be avoided by process control, which may broaden the development of HA and popping boba market. © 2024 Society of Chemical Industry.
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Affiliation(s)
- Hang Li
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, China
- Science Center for Future Foods, Jiangnan University, Wuxi, China
- School of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
- Jiaxing Institute of Future Food, Jiaxing, China
| | - Qinyi Zhang
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, China
- Science Center for Future Foods, Jiangnan University, Wuxi, China
- School of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
- Jiaxing Institute of Future Food, Jiaxing, China
| | - Ling Chen
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, China
- Science Center for Future Foods, Jiangnan University, Wuxi, China
- School of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
- Jiaxing Institute of Future Food, Jiaxing, China
| | - Yongzhi Wang
- Bloomage Biotechnology Corporation Limited, Shanghai, China
| | - Zheng Ai
- Bloomage Biotechnology Corporation Limited, Shanghai, China
| | - Tianmeng Zhang
- Bloomage Biotechnology Corporation Limited, Jinan, China
| | - Fei Liu
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, China
- Science Center for Future Foods, Jiangnan University, Wuxi, China
- School of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
- Jiaxing Institute of Future Food, Jiaxing, China
| | - Fang Zhong
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, China
- Science Center for Future Foods, Jiangnan University, Wuxi, China
- School of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
- Jiaxing Institute of Future Food, Jiaxing, China
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2
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Mo M, Bai X, Liu Z, Huang Z, Xu M, Ma L, Lai W, Mo Q, Xie S, Li Y, Huang Y, Xiao N, Zheng Y. Defect by design: Harnessing the "petal effect" for advanced hydrophobic surface applications. J Colloid Interface Sci 2024; 673:37-48. [PMID: 38875796 DOI: 10.1016/j.jcis.2024.05.192] [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: 01/28/2024] [Revised: 05/15/2024] [Accepted: 05/24/2024] [Indexed: 06/16/2024]
Abstract
HYPOTHESIS In the interfacial wetting boundary, the superhydrophobic surface is often damaged, and the anisotropic wettability of its surface has attracted many researchers' attention. The "petal effect" surface has typical anisotropic wettability. We predict that under the dual conditions of structural defects and high impact velocity, the "petal effect" becomes more adhesive on the surface. EXPERIMENTS This study refers to the droplet state on rose petals, structural defects were constructed on the superhydrophobic surface. This paper studies the influence of macro-structural defects on the wettability change from natural to bionic "lotus effect" to "petal effect" in both static and dynamic angles. FINDINGS Macro defects significantly change the static contact angle of the superhydrophobic surface. The higher the impact velocity of the droplet, the higher the energy dissipation of the "petal effect" surface (DSHS), which improves the adhesion of the surface to the droplet and prolongs the contact time. It is found that the defect structure and high impact velocity will directly affect the deposition and desorption of droplets on the superhydrophobic surface, and they are both essential. This wetting dynamic law is very likely to be helpful in the quantitative design of defect structure scale for dynamic desorption of droplets on superhydrophobic surfaces.
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Affiliation(s)
- Min Mo
- College of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China
| | - Xingjia Bai
- College of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China
| | - Zhonglin Liu
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Zhimin Huang
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Mengxue Xu
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Lanyu Ma
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Wenqin Lai
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Qiufeng Mo
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Songbo Xie
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Yanming Li
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Yifeng Huang
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China
| | - Ning Xiao
- National Key Laboratory of Non-Food Biomass Energy Technology, Guangxi Academy of Sciences, Nanning 530007, China
| | - Yihua Zheng
- Guangxi Key Laboratory of Advanced Microwave Manufacturing Technology, Advanced Materials Industry Institute of Guangxi Academy of Science, Guangxi Academy of Sciences, Nanning 530007, China.
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3
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Wang J, Li L, Lu X, Zhou Y, Zhou J, Jing D. Spreading dynamics of a droplet upon impact with a liquid film containing solid particles. Phys Chem Chem Phys 2024; 26:15717-15732. [PMID: 38767249 DOI: 10.1039/d4cp00072b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
This study examines how a deionized water droplet behaves when it centrally collides with a liquid film containing TiO2 nanoparticles at low impact velocities, aiming to understand how nanoparticles affect droplet spreading, in particular its maximum spreading diameter. Typically, we found that both the spreading velocity and dynamic contact angle of the droplet would be similarly affected by increasing TiO2 nanoparticle concentration. During retraction, the droplet's dimensionless spreading diameter oscillates, with more pronounced oscillations at higher nanoparticle concentrations. Moreover, both the droplet's maximum dimensionless rebound height and dynamic contact angle show similar trends with increasing TiO2 nanoparticle concentration. Interestingly, we proved that the influence of the solid-liquid interaction (Stokes force) on the fluid during the spreading process accounts for less than 2% of the surface energy when the droplet reaches its maximum spreading diameter, indicating a negligible effect on droplet spreading. We hypothesize that the droplet's initial energy is fully converted into surface energy and viscous dissipation at maximum spreading diameter, which involves viscous dissipation both between the fluid and the solid wall surface and the fluid and solid particle surface. Based on this, we developed a model for predicting the droplet's maximum spreading diameter that includes parameters associated with the solid particles. Compared to models in the literature that do not consider the effect of solid particles, our model aligns more closely with experimental data. The results indicate that adding solid particles leads to increased viscous dissipation, which in turn reduces the droplet's maximum spreading diameter.
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Affiliation(s)
- Jiale Wang
- International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
| | - Lei Li
- Chemical Engineering Department, Sichuan University of Science & Engineering, Zigong, Sichuan 643000, China
| | - Xinlong Lu
- International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
| | - Yu Zhou
- International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
| | - Jiandong Zhou
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Dengwei Jing
- International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
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Akbari MJ, Bijarchi MA, Shafii MB. Experimental investigation on the bouncing dynamics of a liquid marble during the impact on a hydrophilic surface. J Colloid Interface Sci 2024; 662:637-652. [PMID: 38367581 DOI: 10.1016/j.jcis.2024.02.060] [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: 10/14/2023] [Revised: 02/02/2024] [Accepted: 02/05/2024] [Indexed: 02/19/2024]
Abstract
Liquid marbles are droplets coated by hydrophobic particles. At low Weber numbers (We), when impacting a hydrophilic surface, the marble may bounce on the substrate repeatedly without any rupturing until the quiescence condition is achieved. The marble bouncing has gained far less attention, although its rich underlying physics is due to the interaction between liquid core, hydrophobic grain, and surrounding air. Accordingly, this research experimentally scrutinizes the marble impact and subsequent bouncing on a hydrophilic surface for the first time. Additionally, the conversion of kinetic, gravitational potential, inertial, and surface energies occurring regularly during the impact is exhaustively surveyed. Moreover, the effect of Weber and gravitational Bond numbers (Bo) on the bouncing time, maximum spreading time, maximum spreading ratio, maximum elongation ratio, and maximum restitution are investigated, which characterize the marble impact and bouncing dynamics. This study is one of the limited investigations exploring the effects of the gravitational Bond number on the results. Dimensionless correlations are proposed for the mentioned parameters based on the experimental data. Furthermore, utilizing the simplifying theoretical presumptions, correlations are suggested based on the scale analysis for the spreading time and maximum spreading ratio. The results imply that the mentioned parameters behave differently at low and moderate Weber numbers, though the distinction is more pronounced in the case of the bouncing time, maximum spreading time and maximum spreading ratio. Although increasing with the Weber number when WeWecr. In addition, the maximum elongation ratio linearly grows with the Weber number.
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Affiliation(s)
- Mohammad Javad Akbari
- Center of Excellence in Energy Conversion (CEEC), Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
| | - Mohammad Ali Bijarchi
- Center of Excellence in Energy Conversion (CEEC), Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
| | - Mohammad Behshad Shafii
- Center of Excellence in Energy Conversion (CEEC), Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran; Sharif Energy, Water and Environment Institute (SEWEI), Tehran, Iran.
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Kumar B, Upadhyay G, Bhardwaj R. Coupled Dynamics of Droplet Impact on a Flexible, Hydrophilic Cantilever Beam. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:18768-18783. [PMID: 38095945 DOI: 10.1021/acs.langmuir.3c02238] [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
We experimentally study the droplet impact on a flexible, hydrophilic cantilever beam. Droplets of water, water-glycerol (1:1 v/v), and glycerol were considered on a copper beam. Side visualization of the droplet impact on the cantilever was carried out by using a high-speed camera. We systematically vary cantilever stiffness to obtain a characteristic time scale of the beam dynamics, that is, shorter on the same order and longer than the characteristic time scale of droplet dynamics. Water droplet spreading reduces with an increase in the beam's flexibility, due to the "springboard effect". Results reveal that a threshold cantilever length exists beyond which the droplet vibration mode "locks-in" to the cantilever vibration mode. During lock-in, the bending energy of the beam increases with an increasing length or decreasing stiffness. The time-varying cantilever deflection exhibits an oscillatory, exponentially decaying response. However, in the case where both time scales are almost the same, we found a two-stage damping in the measurements: a fast, initial damping followed by a slower, damped response. We explain this damped response by the interplay of droplet and cantilever early dynamics. As expected, increasing the droplet viscosity dampens the magnitude of droplet spreading and displacement of the cantilever's tip due to a larger dissipation of kinetic energy in the bulk of the droplet. The decay is exponential in all cases, and the time taken to reduce the spreading and displacement is shorter with a larger viscosity. The damping coefficient is found to inversely scale with the cantilever length or mass. We corroborated the measurements with available analytical models, confirming the hypotheses used to explain the results. Overall, the present study provides fundamental insights into controlling the coupled dynamics of droplet and flexible substrates, with potential applications such as the design of efficient agricultural sprays and wings of microaerial vehicles.
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Affiliation(s)
- Bibek Kumar
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Gaurav Upadhyay
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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6
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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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7
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Peng X, Wang T, Jia F, Sun K, Li Z, Che Z. Singular jets during droplet impact on superhydrophobic surfaces. J Colloid Interface Sci 2023; 651:870-882. [PMID: 37573733 DOI: 10.1016/j.jcis.2023.07.186] [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: 04/25/2023] [Revised: 07/24/2023] [Accepted: 07/28/2023] [Indexed: 08/15/2023]
Abstract
HYPOTHESIS The impact of droplets is prevalent in numerous applications, and jetting during droplet impact is a critical process controlling the dispersal and transport of liquid. New jetting dynamics are expected in different conditions of droplet impact on super-hydrophobic surfaces, such as new jetting phenomena, mechanisms, and regimes. EXPERIMENTS In this experimental study of droplet impact on super-hydrophobic surfaces, the Weber number and the Ohnesorge number are varied in a wide range, and the impact process is analyzed theoretically. FINDINGS We identify a new type of singular jets, i.e., singular jets induced by horizontal inertia (HI singular jets), besides the previously studied singular jets induced by capillary deformation (CD singular jets). For CD singular jets, the formation of the cavity is due to the propagation of capillary waves on the droplet surface; while for HI singular jets, the cavity formation is due to the large horizontal inertia of the toroidal edge during the retraction of the droplet after the maximum spreading. Key steps of the impact process are analyzed quantitatively, including the spreading of the droplet, the formation and the collapse of the spire, the formation and retraction of the cavity, and finally the formation of singular jets. A regime map for the formation of singular jets is obtained, and scaling relationships for the transition conditions between different regimes are analyzed.
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Affiliation(s)
- Xiaoyun Peng
- State Key Laboratory of Engines, Tianjin University, Tianjin, 300350, China
| | - Tianyou Wang
- State Key Laboratory of Engines, Tianjin University, Tianjin, 300350, China; National Industry-Education Platform of Energy Storage, Tianjin University, Tianjin, 300350, China
| | - Feifei Jia
- State Key Laboratory of Engines, Tianjin University, Tianjin, 300350, China
| | - Kai Sun
- State Key Laboratory of Engines, Tianjin University, Tianjin, 300350, China
| | - Zhe Li
- State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin, 300350, China
| | - Zhizhao Che
- State Key Laboratory of Engines, Tianjin University, Tianjin, 300350, China; National Industry-Education Platform of Energy Storage, Tianjin University, Tianjin, 300350, China.
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8
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Bandyopadhyay S, Bakli C, Mukherjee R, Chakraborty S. Damped Oscillatory Dynamics of a Drop Impacting over Oil-Infused Slippery Interfaces─Does the Oil Viscosity Slow it Down? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12826-12834. [PMID: 37642554 DOI: 10.1021/acs.langmuir.3c01689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
A liquid drop impacting on a soft surface is known to exhibit fascinating dynamics that is distinctive from its bounce-back atop a rigid surface. However, while the early spreading of the drop subsequent to its immediate impact with a lubricating liquid layer appears to be reasonably well understood, the later events of retraction and eventual stabilization appear to be poorly addressed. Here, we bring out the nontrivial confluence of the solid substrate wettability and the liquid layer viscosity toward modulating the post-collision dynamics of an impinging liquid drop on a viscous oil-infused surface during its later phase of settlement before arriving at an equilibrium state. Our results reveal that despite an intuitive analogy with the classical phenomenon of damped oscillation, the drop, during its later stages of motion, undergoes dynamical events that may be nontrivially dictated by not only the relative viscosity of the impacting drop and the liquid layer but also the intrinsic wettability of the solid substrate, governing its post-impact settlement via a sequel of spreading-retraction cycles. As a consequence, the viscous liquid layer, instead of providing additional damping, may nonintuitively reduce the effective viscous dissipation so as to hasten the drop's final settlement. These results may turn out to be critical in designing engineered surfaces for tuning the movement of drops in a preferential pathway, bearing decisive implications in the functionalities of liquid lenses, inkjet printing, spray coating and cooling, and several other emerging applications in the realm of lubricated fluidic interfaces.
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Affiliation(s)
- Saumyadwip Bandyopadhyay
- Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721 302, West Bengal, India
| | - Chirodeep Bakli
- School of Energy Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India
| | - Rabibrata Mukherjee
- Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721 302, West Bengal, India
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India
| | - Suman Chakraborty
- Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721 302, West Bengal, India
- Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India
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9
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Kaushal A, Shoval S, Binks BP, Bormashenko E. Universality of Scaling Laws Governing Contact and Spreading Time Spans of Bouncing Liquid Marbles and its Physical Origin. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12488-12496. [PMID: 37604671 DOI: 10.1021/acs.langmuir.3c01710] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
The impact of liquid marbles coated with a diversity of hydrophobic powders with various solid substrates, including hydrophobic, hydrophilic, and superhydrophobic ones, was investigated. The contact time of the bouncing marbles was studied. Universal scaling behavior of the contact time tc as a function of the Weber number (We) was established; the scaling law tc = tc(We) was independent of the kind of powder and the type of solid substrate. The total contact time consists of spreading time and retraction time. It is weakly dependent on We and this is true for all kinds of studied powders and substrates. This observation hints to the surface tension/inertia spring model governing the impact. By contrast, the spreading time ts scales as [Formula: see text], n = 0.28 - 0.30 ± 0.002. We relate the origin of this scaling law to the viscous dissipation occurring within the spreading marbles. The retraction time tr grows weakly with the Weber number. The scaling law was changed at threshold values of We ≅ 15-20. It is reasonable to explain this change with the breaking of the Leidenfrost regime of spreading under high values of We.
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Affiliation(s)
- Abhishek Kaushal
- Chemical Engineering Department, Engineering Faculty, Ariel University, P.O.B. 3, 407000 Ariel, Israel
- Department of Industrial Engineering and Management, Faculty of Engineering, Ariel University, P.O.B. 3, Ariel 407000, Israel
| | - Shraga Shoval
- Department of Industrial Engineering and Management, Faculty of Engineering, Ariel University, P.O.B. 3, Ariel 407000, Israel
| | - Bernard P Binks
- Department of Chemistry, University of Hull, Hull HU6 7RX, U.K
| | - Edward Bormashenko
- Chemical Engineering Department, Engineering Faculty, Ariel University, P.O.B. 3, 407000 Ariel, Israel
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Xiang S, Liu Y, Tang Q, Jin Y, Fan J, Chen L. Impinging blood droplets on different wettable surfaces: Impact phenomena, contact line motion, post-impact oscillation and dried stains. Sci Justice 2023; 63:517-528. [PMID: 37453784 DOI: 10.1016/j.scijus.2023.06.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/04/2023] [Accepted: 06/09/2023] [Indexed: 07/18/2023]
Abstract
Understanding the underlying hydrodynamics of impinging blood droplets and finding out the physical parameters determining the bloodstain characteristics are of great importance in blood related forensic investigations. In this work, the impact of non-Newtonian blood droplets on solid surfaces ranging from lyophilic to superlyophobic was systematically investigated and compared to that of Newtonian droplets with a similar dynamic shear viscosity. We show that impinging blood droplets behave as low-viscosity Newtonian droplets in the short-time spreading, which is dominated by capillary and inertial forces, but their non-Newtonian viscoelasticity would notably affect the droplet retraction and post-impact oscillation occurring in large timescales. Whereas the strong liquid-solid adhesion and the non-Newtonian elongational viscosity hinder droplet recoiling and thus alter the impact phenomena on lyophobic and superlyophobic surfaces, the shear and elongational viscosities are coupled to result in higher damping coefficients of oscillating blood droplets after deposition, in comparison to that of impinging Newtonian droplets. The size of the dried bloodstain was found to be different from both the maximum spreading radius of the droplet that can reach during impact and the final radius of the deposited droplet after oscillation, and their correlations are highly dependent on the impact velocity and surface wettability. Moreover, the morphologic characteristics of the bloodstains would also be changed by varying either the impact velocity or the surface wettability. We envision that these findings can not only find applications in the bloodstain pattern analysis, but also provide useful information for medical diagnosis based on blood droplet test.
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Affiliation(s)
- Shihan Xiang
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Yonghong Liu
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Qingguo Tang
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Yakang Jin
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Jie Fan
- Department of Radiology, Chengdu Seventh People's Hospital, Chengdu 610000, China
| | - Longquan Chen
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China.
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11
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Zhang LZ, Chen X, Yang YR, Wang XD. Impact Dynamics of a Droplet on Superhydrophobic Cylinders Structured with a Macro Ridge. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:6375-6386. [PMID: 37092810 DOI: 10.1021/acs.langmuir.3c00067] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Reducing the contact time of a droplet hitting a solid surface is crucial for many situations. In this work, the dynamic behavior of a low-viscosity droplet on a superhydrophobic surface, which consists of a cylindrical substrate and a macro ridge placed axially on the peak, was numerically investigated via the lattice Boltzmann method. The focus was given to the spreading and the detaching morphology of the droplet at the Weber number We = 0.84-37.8 and the cylinder-to-droplet radius ratio R* = 0.57-5.71. The ridge is found to redistribute the droplet mass and affect the impact outcomes, as well as the contact time. For each R*, a jug rebound, a stretched rebound straddling the ridge, and a split detachment occur sequentially with the increasing We. When R* does not exceed 1.71, the contact time decreases continuously with the increase in We. With R* being taken between 1.71 and 5.14, the contact time initially reduces with We and plateaus after We reaches 10.3. Once R* exceeds 5.14, the split droplets may present as a bestriding shape at We > 30.3 rather than the regular jug shape with a small We. The contact time would be decreased to a second plateau in this case. In most cases, the contact time can be shortened effectively for the droplet on a ridged cylinder compared with that of a smooth cylinder.
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Affiliation(s)
- Ling-Zhe Zhang
- 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
| | - Xu Chen
- 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
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12
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Quintero JSM, Majhy B, Caesar M, Waghmare PR. Electrowetting-Induced Coalescence of Sessile Droplets in Viscous Medium. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:4917-4923. [PMID: 36996262 DOI: 10.1021/acs.langmuir.2c03194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Manipulating the coalescence of microdroplets has recently gained enormous attention in digital microfluidics and biological and chemical industries. Here, coalescence between two sessile droplets is induced by spreading them due to electrowetting. The electrocoalescence dynamics is investigated for a wide range of operating parameters such as electrowetting number, Ohnesorge number, driving frequency, and drop to surrounding medium viscosity ratio. Here, the characteristic time scale from the classical lubrication theory is modified with an additional driving and resisting force due to the electrostatic pressure force and liquid-liquid viscous dissipation, respectively. With the revised characteristic time scale, a universal bridge growth is shown between the two merging droplets following a 1/3 power law during early coalescence followed by a long-range linear variation. To ensure precise control on droplet coalescence, a geometric analysis is also performed to define the initial separation distance.
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Affiliation(s)
- Juan Sebastian Marin Quintero
- Interfacial Science and Surface Engineering Lab (iSSELab), Department of Mechanical Engineering, University of Alberta, Edmonton T6G 2R3, Canada
| | - Butunath Majhy
- Interfacial Science and Surface Engineering Lab (iSSELab), Department of Mechanical Engineering, University of Alberta, Edmonton T6G 2R3, Canada
| | - Markus Caesar
- Interfacial Science and Surface Engineering Lab (iSSELab), Department of Mechanical Engineering, University of Alberta, Edmonton T6G 2R3, Canada
| | - Prashant R Waghmare
- Interfacial Science and Surface Engineering Lab (iSSELab), Department of Mechanical Engineering, University of Alberta, Edmonton T6G 2R3, Canada
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13
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Wang X, Yan X, Du J, Ji B, Jalal Inanlu M, Min Q, Miljkovic N. Spreading dynamics of microdroplets on nanostructured surfaces. J Colloid Interface Sci 2023; 635:221-230. [PMID: 36592502 DOI: 10.1016/j.jcis.2022.12.107] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 12/11/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
HYPOTHESIS Droplet spreading governs various daily phenomena and industrial processes. Insights about microdroplet spreading are limited due to experimental difficulties arising from microdroplet manipulation and substrate wettability control. For droplet sizes approaching the capillary length scale, the gravitational force plays an important role in spreading. In contrast, capillary and viscous forces dominate as the droplet size reduces to smaller length scales. We hypothesize that the dynamic spreading behavior of microdroplets whose radius is far lower than the capillary length differs substantially from established and well understood dynamics. EXPERIMENTS To systematically investigate the spreading dynamics of microdroplets, we develop contact-initiated wetting techniques combined with structuring-independent wettability control to achieve microdroplet (<500 μm) spreading on arbitrary surfaces while eliminating parasitic pinning effects (pining force ∼ 0) and initial impact momentum effects (Weber number ∼ 0). FINDINGS Our experiments reveal that the capillary-driven initial spreading of microdroplets is shorter, with significantly reduced oscillation dampening, when compared to millimeter-scale droplets. Furthermore, spreading along with capillary wave propagation results in coupling between the spreading velocity and dynamic contact angle at the contact line. These findings, along with our proposed microdroplet manipulation platform, may find application in microscale heat transfer, advanced manufacturing, and aerosol transmission studies.
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Affiliation(s)
- Xiong Wang
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; 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, China
| | - Xiao Yan
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
| | - 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, China
| | - Bingqiang Ji
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Mohammad Jalal Inanlu
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - 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, China.
| | - Nenad Miljkovic
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; Department of Electrical Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
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14
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Liu H, Zheng N, Chen J, Yang D, Wang J. Study on the Bouncing Behaviors of a Non-Newtonian Fluid Droplet Impacting on a Hydrophobic Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3979-3993. [PMID: 36897569 DOI: 10.1021/acs.langmuir.2c03298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The control of a droplet bouncing on a substrate is of great importance not only in academic research but also in practical applications. In this work, we focus on a particular type of non-Newtonian fluid known as shear-thinning fluid. The rebound behaviors of shear-thinning fluid droplets impinging on a hydrophobic surface (equilibrium contact angle θeq ≈ 108°and contact angle hysteresis Δθ ≈ 20°) have been studied experimentally and numerically. The impact processes of Newtonian fluid droplets with various viscosities and non-Newtonian fluid droplets with dilute xanthan gum solutions were recorded by a high-speed imaging system under a range of Weber numbers (We) from 12 to 208. A numerical model of the droplet impact on the solid substrate was also constructed using a finite element scheme with the phase field method (PFM). The experimental results show that unlike the Newtonian fluid droplets where either partial rebound or deposition occurs, complete rebound behavior was observed for non-Newtonian fluid droplets under a certain range of We. Moreover, the minimum value of We required for complete rebound increases with xanthan concentration. The numerical simulations indicate that the shear-thinning property significantly affects the rebound behavior of the droplets. As the amount of xanthan increases, the high shear rate regions shift to the bottom of the droplet and the receding of the contact line accelerates. Once the high shear rate region appears only near the contact line, the droplet tends to fully rebound even on a hydrophobic surface. Through the impact maps of various droplets, we found that the maximum dimensionless height Hmax* of the droplet increases almost linearly with We as Hmax* ∼ αWe. In addition, a critical value Hmax, c* for the distinction between deposition and rebound for droplets on the hydrophobic surface has been theoretically derived. The prediction of the model shows good consistency with the experimental results.
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Affiliation(s)
- Hailong Liu
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang, China, 212013
| | - Nuo Zheng
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang, China, 212013
| | - Jiaqi Chen
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang, China, 212013
| | - Ding Yang
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang, China, 212013
| | - Junfeng Wang
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang, China, 212013
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15
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Satpathi NS, Nampoothiri KN, Sen AK. Effects of surface acoustic waves on droplet impact dynamics. J Colloid Interface Sci 2023; 641:499-509. [PMID: 36948105 DOI: 10.1016/j.jcis.2023.03.058] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 03/02/2023] [Accepted: 03/08/2023] [Indexed: 03/13/2023]
Abstract
HYPOTHESIS Surface acoustic waves (SAW) propagating along a solid surface can significantly affect the dynamics of droplet impact. Although droplet impact in presence of SAW has been attempted recently, here, we investigate the effects of surface wettability, droplet size, impact velocity, and SAW power on the impact and spreading dynamics along with post-impact oscillation dynamics of a drop. EXPERIMENTS Here, we study droplet impact on a surface exposed to traveling SAW produced using an interdigitated electrode patterned on a piezoelectric substrate. The effects of Weber number (We), surface wettability, and SAW power on the impact and spreading dynamics and post-impact oscillation dynamics are studied. FINDINGS Our study unravels that the interplay between capillary and viscous forces, and inertia forces arising due to pre-impact kinetic energy and SAW-induced bulk acoustic streaming underpins the phenomena. Remarkably, we find that the effect of SAW on droplet impact dynamics is predominant in the case of a hydrophilic (HPL) substrate at a higher SAW power and smaller We and hydrophobic (HPB) substrate irrespective of SAW power. Our study reveals that the maximum droplet spreading diameter increases with SAW power at smaller We for an HPL surface whereas it is independent of SAW power at higher We. Post-impact oscillation of a droplet over an HPL surface is found to be overdamped with a smaller amplitude compared to an HPB substrate, and a faster decay in oscillation amplitude is observed in the case of an HPB surface and higher We. Our study provides an improved understanding of droplet impact on a surface exposed to SAW that may find relevance in various practical applications.
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Affiliation(s)
- N S Satpathi
- Micro Nano Bio Fluidics Unit, Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India
| | - K N Nampoothiri
- Micro Nano Bio Fluidics Unit, Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India
| | - A K Sen
- Micro Nano Bio Fluidics Unit, Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India.
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16
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Droplet impact on a hydrophobic surface integrated with electrowetting technique. Colloids Surf A Physicochem Eng Asp 2023. [DOI: 10.1016/j.colsurfa.2022.130423] [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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17
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Shu Y, Chu F, Hu Z, Gao J, Wu X, Dong Z, Feng Y. Superhydrophobic Strategy for Nature-Inspired Rotating Microfliers: Enhancing Spreading, Reducing Contact Time, and Weakening Impact Force of Raindrops. ACS APPLIED MATERIALS & INTERFACES 2022; 14:57340-57349. [PMID: 36512411 DOI: 10.1021/acsami.2c16662] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Wind-dispersal of seeds is a remarkable strategy in nature, enlightening the construction of microfliers for environmental monitoring. However, the flight of these microfliers is greatly affected by climatic conditions, especially in rainy days, they suffer serious raindrop impact. Here, a hierarchical superhydrophobic surface is fabricated and a novel strategy is demonstrated that the superhydrophobic coating can enhance spreading while reduce contact time and impact force of raindrops, all of which are beneficial for the rotating microfliers. When the surface rotating speed exceeds a critical value, the effect of centrifugal force becomes considerable so that the droplet spreading is enhanced. The rotating superhydrophobic surface can rotate an impacting droplet by the tangential drag force from the air boundary layer, and the rotation of the droplet generates a negative pressure zone inside it, reducing the contact time by more than 30%. The impact force by the droplet on the rotating superhydrophobic surface also has a remarkable reduction of 53% compared to that on unprocessed hydrophilic surfaces, which helps maintain the flight stability of the microfliers. This work pioneers in revealing the droplet impact effect on rotating microflier surfaces and demonstrates the effectiveness of protecting microfliers with superhydrophobic coatings, which shall guide the manufacture and flight of microfliers in rainy conditions.
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Affiliation(s)
- Yifu Shu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
| | - Zhifeng Hu
- Department of Energy and Power Engineering, Tsinghua University, Beijing100084, China
| | - Jie Gao
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
| | - Xiaomin Wu
- Department of Energy and Power Engineering, Tsinghua University, Beijing100084, China
| | - Zhichao Dong
- CAS Key Laboratory of Bio-Inspired Materials and Interfacial Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing100190, China
| | - Yanhui Feng
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing100083, China
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18
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Rong F, He L, Lü Y, Wang C, Wang S. Study on the adhesion behaviour of oil droplets in water on solid surfaces with different wettability and inclination. CAN J CHEM ENG 2022. [DOI: 10.1002/cjce.24743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Feng Rong
- College of Pipeline and Civil Engineering China University of Petroleum Qingdao China
| | - Limin He
- College of Pipeline and Civil Engineering China University of Petroleum Qingdao China
- Shandong Provincial Key Laboratory of Oil & Gas Storage and Transportation Safety Qingdao China
- Surface Engineering Pilot Test Center CNPC Daqing China
| | - Yuling Lü
- College of Pipeline and Civil Engineering China University of Petroleum Qingdao China
- Shandong Provincial Key Laboratory of Oil & Gas Storage and Transportation Safety Qingdao China
- Surface Engineering Pilot Test Center CNPC Daqing China
| | - Ce Wang
- College of Pipeline and Civil Engineering China University of Petroleum Qingdao China
| | - Shipeng Wang
- College of Pipeline and Civil Engineering China University of Petroleum Qingdao China
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19
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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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20
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Hu Z, Ding S, Zhang X, Wu X. Dynamic behavior and maximum width of impact droplets on single-pillar superhydrophobic surfaces. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129355] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Mehrizi AA, Lin S, Sun L, Wang Y, Chen L. Penetration and ligament formation of viscoelastic droplets impacting on the superhydrophobic mesh. Sci Rep 2022; 12:11920. [PMID: 35831383 PMCID: PMC9278331 DOI: 10.1038/s41598-022-15645-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 06/27/2022] [Indexed: 11/09/2022] Open
Abstract
Spraying occurs by the impact of water droplets on the superhydrophobic wire meshes by liquid penetration during the spreading and recoiling. We have shown that adding a small amount of high molecular weight polymer (PEO) alters the ligaments formation and stabilizes them due to its high elasticity. Consequently, it suppresses droplet spray during droplet spreading and recoiling (recoil penetration). In the wide range of the impact velocities, the penetrated ligaments retracted back to the mesh after reaching the maximum length and eventually merged with the droplet on the mesh. The empirical fitting shows that the ligament evolution follows the parallel spring-dashpot model of Kelvin–Voigt. The additive polymer also changes the recoil penetration mechanisms from cavity collapse to cavity detachment due to the higher retraction velocity of the cavity near the mesh that is induced by the upward flow formed by the retraction of the ligaments to the mother droplet. A model based on mass conservation is proposed to calculate the variation of the maximum ligament size.
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Affiliation(s)
- Abbasali Abouei Mehrizi
- School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China.
| | - Shiji Lin
- School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Lijie Sun
- School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Yile Wang
- School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Longquan Chen
- School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China.
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22
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Yada S, Lacis U, van der Wijngaart W, Lundell F, Amberg G, Bagheri S. Droplet Impact on Asymmetric Hydrophobic Microstructures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7956-7964. [PMID: 35737474 PMCID: PMC9261186 DOI: 10.1021/acs.langmuir.2c00561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 06/09/2022] [Indexed: 06/15/2023]
Abstract
Textured hydrophobic surfaces that repel liquid droplets unidirectionally are found in nature such as butterfly wings and ryegrass leaves and are also essential in technological processes such as self-cleaning and anti-icing. In many occasions, surface textures are oriented to direct rebounding droplets. Surface macrostructures (>100 μm) have often been explored to induce directional rebound. However, the influence of impact speed and detailed surface geometry on rebound is vaguely understood, particularly for small microstructures. Here, we study, using a high-speed camera, droplet impact on surfaces with inclined micropillars. We observed directional rebound at high impact speeds on surfaces with dense arrays of pillars. We attribute this asymmetry to the difference in wetting behavior of the structure sidewalls, causing slower retraction of the contact line in the direction against the inclination compared to with the inclination. The experimental observations are complemented with numerical simulations to elucidate the detailed movement of the drops over the pillars. These insights improve our understanding of droplet impact on hydrophobic microstructures and may be useful for designing structured surfaces for controlling droplet mobility.
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Affiliation(s)
- Susumu Yada
- FLOW
Centre, Department of Engineering Mechanics, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden
| | - Ugis Lacis
- FLOW
Centre, Department of Engineering Mechanics, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden
| | - Wouter van der Wijngaart
- Division
of Micro and Nanosystems, Royal Institute
of Technology (KTH), 100 44 Stockholm, Sweden
| | - Fredrik Lundell
- FLOW
Centre, Department of Engineering Mechanics, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden
| | - Gustav Amberg
- FLOW
Centre, Department of Engineering Mechanics, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden
- Södertörn
University, 141 89 Stockholm, Sweden
| | - Shervin Bagheri
- FLOW
Centre, Department of Engineering Mechanics, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden
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23
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Droplet Spreading Characteristics on Ultra-Slippery Solid Hydrophilic Surfaces with Ultra-Low Contact Angle Hysteresis. COATINGS 2022. [DOI: 10.3390/coatings12060755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
Dynamic interactions of the droplet impact on a solid surface are essential to many emerging applications, such as electronics cooling, ink-jet printing, water harvesting/collection, anti-frosting/icing, and microfluidic and biomedical device applications. Despite extensive studies on the kinematic features of the droplet impact on a surface over the last two decades, the spreading characteristics of the droplet impact on a solid hydrophilic surface with ultra-low contact angle hysteresis are unclear. This paper clarifies the specific role of the contact angle and contact angle hysteresis at each stage of the droplet impact and spreading process. The spreading characteristics of the droplet impact on an ultra-slippery hydrophilic solid surface are systematically compared with those on plain hydrophilic, hydroxylated hydrophilic, and plain hydrophobic surfaces. The results reveal that the maximum spreading factor (βmax) of impacting droplets is mainly dependent on the contact angle and We. βmax increases with the increase in We and the decrease in the contact angle. Low contact angle hysteresis can decrease the time required to reach the maximum spreading diameter and the time interval during which the maximum spreading diameter is maintained when the contact angles are similar. Moreover, the effect of the surface inclination angle on the spreading and slipping dynamics of impacting droplets is investigated. With the increase in the inclination angle and We, the gliding distance of the impacting droplet becomes longer. Ultra-low contact angle hysteresis enables an impacting droplet to slip continuously on the ultra-slippery hydrophilic surface without being pinned to the surface. The findings of this work not only show the important role of the surface wettability in droplet spreading characteristics but also present a pathway to controlling the dynamic interactions of impacting droplets with ultra-slippery hydrophilic surfaces.
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24
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Du J, Wang X, Li Y, Min Q. How an Oxide Layer Influences the Impact Dynamics of Galinstan Droplets on a Superhydrophobic Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5645-5655. [PMID: 35482446 DOI: 10.1021/acs.langmuir.2c00225] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
When exposed to air, gallium-based alloys rapidly form a thin oxide layer with viscoelasticity and high adhesion. Although previous work demonstrated that an oxide layer inhibits liquid metal droplet rebound, there is still a lack of a quantitative study to elaborate how an oxide layer affects the impact dynamics. To address this issue, we experimentally investigate Galinstan droplet impingement on a superhydrophobic CuO nanoblade surface and physically explain the difference in the dynamic characteristics of oxidized and unoxidized droplets. Experimental results show that the effect of an oxide layer becomes prominent during the retraction phase. The high adhesion significantly suppresses retraction and rebound, while the elastic response prevents a droplet from sufficiently stretching and maintains the stability of the morphology. More importantly, we systematically and quantitatively explore the influence of an oxide layer on several critical impact parameters, which contributes to a comprehensive understanding of the impact dynamics of liquid metal droplets. It is indicated that an oxide layer has little effect on the maximum spreading factor and spreading time, whereas it causes a 45% reduction of the restitution coefficient and a 36% increase in contact time. Notably, the scaling laws that describe the critical impact parameters of unoxidized droplets show good agreement with the ones known from ordinary Newtonian fluids.
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Affiliation(s)
- 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
| | - 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, Tsinghua University, Beijing 100084, China
| | - 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
| | - 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
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25
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Guimarães B, Silva J, Fernandes C, Figueiredo D, Carvalho O, Miranda G, Silva F. Understanding drop spreading behaviour on WC-10wt%Co cutting tools – an experimental and numerical study. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.128268] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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26
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Díaz D, Garcia-Gonzalez D, Bista P, Weber SAL, Butt HJ, Stetten A, Kappl M. Charging of drops impacting onto superhydrophobic surfaces. SOFT MATTER 2022; 18:1628-1635. [PMID: 35113106 DOI: 10.1039/d1sm01725j] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
When neutral water drops impact and rebound from superhydrophobic surfaces, they acquire a positive electrical charge. To measure the charge, we analyzed the trajectory of rebounding drops in an external electric field by high-speed video imaging. Although this charging phenomenon has been observed in the past, little is known about the controlling parameters for the amount of drop charging. Here we investigate the relative importance of five of these potential variables: impact speed, drop contact area, contact line retraction speed, drop size, and type of surface. We additionally apply our previously reported model for sliding drop electrification to the case of impacting drops, suggesting that the two cases contain the same charge separation mechanism at the contact line. Both our experimental results and our theoretical model indicate that maximum contact area is the dominant control parameter for charge separation.
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Affiliation(s)
- Diego Díaz
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Diana Garcia-Gonzalez
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
- Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, University of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands
| | - Pravash Bista
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Stefan A L Weber
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
- Department of Physics, Johannes Gutenberg University, Staudingerweg 10, 55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Amy Stetten
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Michael Kappl
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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27
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Hu Z, Chu F, Lin Y, Wu X. Contact Time of Droplet Impact on Inclined Ridged Superhydrophobic Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:1540-1549. [PMID: 35072484 DOI: 10.1021/acs.langmuir.1c03001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Superhydrophobic surfaces decorated with macrostructures have attracted extensive attention due to their excellent performance of reducing the contact time of impacting droplets. In many practical applications, the surface is not perpendicular to the droplet impact direction, but the impacting dynamics in such scenarios still remain mysterious. Here, we experimentally investigate the dynamics of droplet impact on inclined ridged superhydrophobic surfaces and reveal the effect of Wen (the normal Weber number) and α (the inclination angle) on the contact time τ. As Wen increases, τ first decreases rapidly until a platform is reached; if Wen continues to increase, τ further reduces to a lower platform, indicating a three-stage variation of τ in low, middle, and high Wen regions. In the middle and high Wen regions, the contact time is reduced by 30 and 50%, respectively, and is dominated by droplet spreading/retraction in the tangential and lateral directions, respectively. A quantitative analysis demonstrates that τ in the middle and high Wen regions is independent of Wen and α, while the range of middle and high Wen regions is related to α. When α < 30°, increasing α narrows the middle Wen region and enlarges the high Wen region; when α ≥ 30°, the two Wen regions remain unchanged. In addition, droplet sliding is hindered by the friction and is affected by the droplet morphology in the high Wen region. Overall, the synergistic effect of the surface inclination and macrostructures effectively promotes the detachment of impacting droplets on superhydrophobic surfaces, which provides guidance for applications of superhydrophobic surfaces.
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Affiliation(s)
- 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
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, 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
| | - 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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28
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Tran H, He Z, Sakakeeny J, Ling Y, Pack MY. Oscillation Dynamics of Drops on Immiscible Thin Liquid Films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:1243-1251. [PMID: 35025520 DOI: 10.1021/acs.langmuir.1c03029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
While drop oscillation dynamics has been widely studied for many decades, the influence of a moving contact line on the oscillation modes of drops remains underexplored. Herein, we report the oscillation dynamics of drops on thin liquid films with different viscosities where lower viscosities provide a slipping surface and higher viscosities immobilize the contact line. A gently deposited drop onto an oil film undergoes shape oscillations due to capillarity, where the frequency, amplitude, and apparent contact angle are tracked via a high-speed camera. This study demonstrates that restraining the mobility of the drop contact line by increasing the viscosity of a thin oil film underneath the drop increases the extent of the drop oscillation time as well as affecting the natural frequency of the drop oscillation. The drop oscillation time was defined by the time at which the changes in the drop height dropped to values less than 1% of the equilibrium height. The experimental results for the first longitudinal mode oscillation frequencies as a function of the equilibrium contact angles for the pinning and slipping contact lines were in good agreement with previously reported numerical simulations and model predictions.
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Affiliation(s)
- Huy Tran
- Department of Mechanical Engineering, Baylor University, One Bear Place #97356, Waco, Texas 76798, United States
| | - Ziwen He
- Department of Mechanical Engineering, Baylor University, One Bear Place #97356, Waco, Texas 76798, United States
| | - Jordan Sakakeeny
- Department of Mechanical Engineering, Baylor University, One Bear Place #97356, Waco, Texas 76798, United States
| | - Yue Ling
- Department of Mechanical Engineering, Baylor University, One Bear Place #97356, Waco, Texas 76798, United States
| | - Min Y Pack
- Department of Mechanical Engineering, Baylor University, One Bear Place #97356, Waco, Texas 76798, United States
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29
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Nampoothiri KN, Satpathi NS, Sen AK. Surface acoustic wave-based generation and transfer of droplets onto wettable substrates. RSC Adv 2022; 12:23400-23410. [PMID: 36090390 PMCID: PMC9382648 DOI: 10.1039/d2ra04089a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 08/09/2022] [Indexed: 11/21/2022] Open
Abstract
Fluid manipulation using surface acoustic waves (SAW) has been utilized as a promising technique in the field of microfluidics due to its numerous advantages, over other active techniques, such as low power requirement, facile fabrication methods, and non-invasive nature. Even though SAW-based generation of micron-sized droplets through atomization has been studied, the role of substrate wettability on the characteristics of the transferred droplets has not been explored to date. Here, we study the generation and effective transfer of micron-sized droplets using SAW onto wettable substrates whose water contact angles vary from 5° to 145°. The characteristics of transferred droplets after impacting the wettable substrates are characterized in terms of the contact line diameter and polydispersity index. A theoretical model is formulated to predict the initial average size of the transferred droplets on the wettable substrates of different contact angles. The variation of polydispersity and number density with contact angle is explained by considering droplet coalescence and bouncing. The relevance of the technique in biological assays is demonstrated by transferring droplets of streptavidin protein samples onto a substrate. Investigation of surface acoustic wave-based generation and transfer of droplets onto wettable substrates is carried out and explained in terms of polydispersity index. Transfer of biomolecules is demonstrated to highlight the technique.![]()
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Affiliation(s)
| | - Niladri Sekhar Satpathi
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
| | - Ashis Kumar Sen
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
- Micro Nano Bio Fluidics Group, Indian Institute of Technology Madras, Chennai-600036, India
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30
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Bao Z, Zeng A, Gao T, Gao Y, He Q, Huang Y, Chou J, Yu L, Zhang C, Du F. Controlling impact behavior on superhydrophobic surfaces for droplets of nonionic surfactants by tailoring hydrophilic chain length. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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31
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Yun S. Effect of Viscosity on Bouncing Dynamics of Elliptical Footprint Drops on Non-Wettable Ridged Surfaces. Polymers (Basel) 2021; 13:polym13244296. [PMID: 34960845 PMCID: PMC8708435 DOI: 10.3390/polym13244296] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 11/22/2021] [Accepted: 12/07/2021] [Indexed: 11/16/2022] Open
Abstract
An initial drop shape can alter the bouncing dynamics and significantly decrease the residence time on superhydrophobic surfaces. Elliptical footprint drops show asymmetric dynamics owing to a pronounced flow driven by the initial drop shape. However, the fundamental understanding of the effect of viscosity on the asymmetric dynamics has yet to be investigated, although viscous liquid drop impact on textured surfaces is of scientific and industrial importance. Here, the current study focuses on the impact of elliptical footprint drops with various liquid properties (density, surface tension, and viscosity), drop sizes, and impact velocities to study the bouncing dynamics and residence time on non-wettable ridged surfaces numerically by using a volume-of-fluid method. The underlying mechanism behind the variation in residence time is interpreted by analyzing the shape evolution, and the results are discussed in terms of the spreading, retraction, and bouncing. This study provides an insight on possible outcomes of viscous drops impinging on non-wettable surfaces and will help to design the desired spraying devices and macro-textured surfaces under different impact conditions, such as icephobic surfaces for freezing rain or viscous liquids.
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Affiliation(s)
- Sungchan Yun
- Department of Mechanical Engineering, Korea National University of Transportation, Chungju 27469, Korea
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32
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Satpathi NS, Malik L, Ramasamy AS, Sen AK. Drop Impact on a Superhydrophilic Spot Surrounded by a Superhydrophobic Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:14195-14204. [PMID: 34802243 DOI: 10.1021/acs.langmuir.1c02654] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The spatial variation in the wettability of a surface can have a significant effect on the spreading and retraction behavior of an impacting droplet and hence the overall impact dynamics. Although composite surfaces have proven applications, there is a lack of understanding of droplet impact on surfaces with a sudden jump in wettability. Here, we study the behavior of a liquid drop impacting a composite surface having a superhydrophilic (SHL) spot surrounded by a superhydrophobic (SHB) region. We find that the droplet exhibits different regimes: no-splitting, jetting, and splashing, depending upon the spot size (βs) and the Weber number (We). At a smaller βs, the behavior shifts from the stable to jetting regime and then to the splashing regime, with increasing We. We find that by increasing the value of βs, one can avoid the undesirable splashing and jetting regimes and attain a stable regime even at a higher We. Our study reveals that βs has a significant influence on the maximum spreading diameter βmax at a smaller We but a negligible effect at a higher We. We show that the dominance of capillary energy at a smaller We and viscous energy at a higher We underpins the phenomena. We employ an energy conservation approach to develop an analytical model to predict βmax on a composite SHL-SHB surface by considering the total energy of the system before the impact and at the maximum spread position. We find K = (Re1/2/We) emerges as a key parameter in the model that accurately predicts the experimentally measured βmax. Our study reveals the existence of an inertia-viscous dominated regime at a smaller K and an inertia-capillary dominated regime at a larger K. The outcome of our study may find applications in stable and precise positioning of impacting droplets.
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Affiliation(s)
- Niladri Sekhar Satpathi
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036 Tamil Nadu, India
| | - Lokesh Malik
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036 Tamil Nadu, India
| | - Alwar Samy Ramasamy
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036 Tamil Nadu, India
| | - Ashis Kumar Sen
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036 Tamil Nadu, India
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33
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Du J, Wang X, Li Y, Min Q. Maximum spreading of liquid droplets impact on concentric ring-textured surfaces: Theoretical analysis and numerical simulation. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127647] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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34
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Yang C, Cao W, Yang Z. Study on dynamic behavior of water droplet impacting on super-hydrophobic surface with micro-pillar structures by VOF method. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127634] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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35
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Hassan MR, Wang C. Spreading Dynamics of an Impinging Ferrofluid Droplet on Hydrophilic Surfaces under Uniform Magnetic Fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:13331-13345. [PMID: 34730963 DOI: 10.1021/acs.langmuir.1c01943] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This paper reports a numerical investigation on the spreading dynamics of an impinging ferrofluid droplet on solid hydrophilic surfaces (i.e., θw ≤ 60°) in the presence of uniform magnetic fields. A finite element method-based commercial solver is implemented to perform several numerical simulations, which uses a phase-field (PF) method to couple both the flow and magnetic fields. The results demonstrate that a uniform magnetic field is capable of controlling the spreading dynamics of an impinging droplet on hydrophilic substrates. Additionally, the application of a magnetic field results in the generation of a steady-state droplet shape with a reduced base diameter and an increased apex height at higher magnetic Bond numbers at the end of the spreading process. Moreover, as the viscosity of the droplet decreases, the droplet experiences an increase in its primary spreading diameter, which can be even reduced through the implementation of a vertical uniform magnetic field. Additionally, an oscillatory motion appears in a droplet during the spreading phenomenon at lower Ohnesorge numbers (i.e., Oh = 0.023), which is further sustained for a longer period of time in the relaxation phase with increased amplitudes in the case of an extremely low-viscosity droplet (i.e., Oh = 0.002) before attaining a final equilibrium shape. Furthermore, at Oh = 0.002, the droplet undergoes a breakup event after the impact for a short period of time, while the magnetic field induces an elastic behavior in a droplet at lower viscosities (i.e., Oh = 0.023) during the free fall under gravity.
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Affiliation(s)
- Md Rifat Hassan
- Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 400 W. 13th St., Rolla, Missouri 65409, United States
| | - Cheng Wang
- Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 400 W. 13th St., Rolla, Missouri 65409, United States
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36
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Giorgi ML, Duval H, Balabane M. The proper orthogonal decomposition: A powerful tool for studying drop oscillations. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:113903. [PMID: 34852554 DOI: 10.1063/5.0056004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 10/08/2021] [Indexed: 06/13/2023]
Abstract
Liquid metal drops are released onto different wettable solid substrates. Their post-impact oscillations are recorded at 1000 images/s as soon as the triple line is at rest. The proper orthogonal decomposition (POD) is used to get and identify the frequencies involved. The POD is a technique widely used in the fluid dynamics community to study turbulent flows, but it is not used to determine droplet-free oscillation frequencies. The vertical and horizontal vibration frequencies of the sessile drop center of mass are successfully extracted from the images by POD. The first POD mode captures the vertical displacement frequency, and the second or third POD mode captures the horizontal displacement frequency of the drop center of mass. The spatial structure of the modes is the characteristic of the vertical and horizontal movement. Therefore, the POD can be used instead of the interface displacement tracking to determine the free oscillation frequencies of liquid metal drops and, more generally, of any vibrating sessile drops. As it is a standardized method, it can be used with confidence for routine measurements, especially for sensors.
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Affiliation(s)
- M-L Giorgi
- CentraleSupélec, Université Paris Saclay, 3 Rue Joliot-Curie, 91192 Gif-sur-Yvette Cedex, France
| | - H Duval
- CentraleSupélec, Université Paris Saclay, 3 Rue Joliot-Curie, 91192 Gif-sur-Yvette Cedex, France
| | - M Balabane
- University of Paris 13, Laboratoire Analyse, Géométrie et Applications, Université Paris 13, Villetaneuse 93430, France
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37
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Mao P, Gao S, Liu W, Liu Z. Head-on Collision of Two Nanodroplets on a Solid Surface: A Molecular Dynamics Simulation Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12346-12355. [PMID: 34648710 DOI: 10.1021/acs.langmuir.1c01849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Most researchers focus on the collision of a single droplet with a solid surface, while it is common for a droplet to collide with a sessile droplet on a solid surface in reality. This study performed the head-on collision of two nanodroplets on a solid surface using the molecular dynamics simulation method. The effects of impact velocity, interaction intensity between solid and liquid atoms, and the solid fraction of the surface on the collision process are studied with independent simulation cases. The maximum spreading factor and the dimensionless maximum spreading time are recorded and calculated to describe the collision process quantitatively. The simulation results indicate that the maximum spreading factor depends more on the solid fraction than the interaction intensity since it does not fundamentally change the wetting state of the droplet at its maximum spreading state. Because of two different effects, the maximum dimensionless spreading time decreases first and then increases with the interaction intensity, and both effects weaken with the increase of impact velocity. As the solid fraction increases, the maximum spreading factor increases significantly at high impact velocity, and the maximum dimensionless spreading time first decreases and then increases because the wetting state of the coalescent droplet at the maximum spreading moment gradually changes from the Wenzel state to the Cassie state. In general, the initial wetting state of the sessile droplet and the wetting state of the coalescent droplet at the maximum spreading moment have important effects on the maximum spreading factor and the maximum spreading time. We establish a theoretical prediction model for the maximum spreading factor on a smooth surface based on energy conservation with quite good accuracy. This research has improved our understanding of the head-on collision process of two nanodroplets on a solid surface.
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Affiliation(s)
- Peng Mao
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Shan Gao
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Wei Liu
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhichun Liu
- School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
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38
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The dynamical behaviors of water drop impacting and bouncing on an inclined hydrophobic surface. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127087] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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39
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Yada S, Allais B, van der Wijngaart W, Lundell F, Amberg G, Bagheri S. Droplet Impact on Surfaces with Asymmetric Microscopic Features. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10849-10858. [PMID: 34469168 PMCID: PMC8447403 DOI: 10.1021/acs.langmuir.1c01813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The impact of liquid drops on a rigid surface is central in cleaning, cooling, and coating processes in both nature and industrial applications. However, it is not clear how details of pores, roughness, and texture on the solid surface influence the initial stages of the impact dynamics. Here, we experimentally study drops impacting at low velocities onto surfaces textured with asymmetric (tilted) ridges. We found that the difference between impact velocity and the capillary speed on a solid surface is a key factor of spreading asymmetry, where the capillary speed is determined by the friction at a moving three-phase contact line. The line-friction capillary number Caf = μfV0/σ (where μf,V0, and σ are the line friction, impact velocity, and surface tension, respectively) is defined as a measure of the importance of the topology of surface textures for the dynamics of droplet impact. We show that when Caf ≪ 1, the droplet impact is asymmetric; the contact line speed in the direction against the inclination of the ridges is set by line friction, whereas in the direction with inclination, the contact line is pinned at acute corners of the ridges. When Caf ≫ 1, the geometric details of nonsmooth surfaces play little role.
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Affiliation(s)
- Susumu Yada
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
| | | | | | - Fredrik Lundell
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
| | - Gustav Amberg
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
- Södertörn
University, 141 89 Stockholm, Sweden
| | - Shervin Bagheri
- Department
of Engineering Mechanics, Royal Institute
of Technology, 100 44 Stockholm, Sweden
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40
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Singh RK, Mahato LK, Mandal DK. Airflow-Assisted Impact of Drops of Various Viscosities: The Role of Viscous Dissipation, Normal Imposed Pressure, and Shear Flow of Air. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9504-9517. [PMID: 34319753 DOI: 10.1021/acs.langmuir.1c01367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The role of liquid viscosity on the spreading for an airflow-assisted impact of drops on a surface is investigated. The spreading diameter is found to increase with the Reynolds number of the airflow (Reair) for a given viscosity and impact Weber number (We) compared to the still air. The increment is higher at a low We for viscous drops, whereas the effect of Reair dominates at the intermediate We as the viscosity decreases. Two extra forces, the normal imposed pressure and shear force of air, act on the drop and influence the spreading along with the viscous dissipation. The drop's curvature decreases depending on the viscosity and impact velocity while spreading. Large-scale eddies near the drop-surface region are observed due to the separation of the incident airflow. The formation of eddies signifies low-pressure zones, which extract the trapped air, causing the spreading diameter of the viscous drop to increase at a low We. With the increase in the We, the lamella thickness of low-viscosity drops decreases and is pushed out by the air shear causing the spreading factor to increase. The boundary layer thickness is estimated using the energy balance method to predict the maximum spreading factor. The prediction compares well with the experimental one for higher viscosities. The accuracy improves when the effect of low pressure is incorporated. To confirm, the experimental spreading is compared with that obtained from three existing models, and one, which considers the influence, is observed to provide a better prediction.
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Affiliation(s)
- Ramesh Kumar Singh
- Department of Mechanical Engineering, Indian Institute of Technology (ISM), Dhanbad 826 004, India
| | - Lukesh Kumar Mahato
- Department of Mechanical Engineering, Indian Institute of Technology (ISM), Dhanbad 826 004, India
| | - Deepak Kumar Mandal
- Department of Mechanical Engineering, Indian Institute of Technology (ISM), Dhanbad 826 004, India
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41
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Experimental and theoretical investigation of the spreading behaviors of oil droplets on the surfaces with different wettabilities. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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42
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Wang LZ, Zhou A, Zhou JZ, Chen L, Yu YS. Droplet impact on pillar-arrayed non-wetting surfaces. SOFT MATTER 2021; 17:5932-5940. [PMID: 34041518 DOI: 10.1039/d1sm00354b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Droplet impact on pillar-arrayed polydimethylsiloxane (PDMS) surfaces with different solid fractions was studied. The lower and upper limits of Weber number, We, for complete rebound of impacting droplets decreased with decreasing solid fractions. Gaps were visible during the spreading and retraction processes of bouncing droplets on the surface with a solid fraction of 0.06 while no gaps were observed during the retraction process when We was greater than its upper limit, indicating that there existed a transition from the Cassie-Baxter wetting state to the Wenzel wetting state. Therefore, a novel model accounting for the penetration of a liquid into the cavities between the pillars was developed to predict the upper limit of the impact velocity of bouncing droplets. At high We, partial rebound was observed for surfaces with solid fractions of 0.50 and 0.20 while a sticky state was observed for the surface with a solid fraction of 0.06. Moreover, surface roughness has a great influence on the contact time of bouncing droplets. Besides, the maximum spreading parameter was found to follow a scaling law of We1/4.
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Affiliation(s)
- Long-Zan Wang
- Department of Mechanics, School of Civil Engineering, Architecture and Environment, Hubei University of Technology, Wuhan 430068, P. R. China.
| | - An Zhou
- Department of Mechanics, School of Civil Engineering, Architecture and Environment, Hubei University of Technology, Wuhan 430068, P. R. China.
| | - Jin-Zhi Zhou
- Department of Mechanics, School of Civil Engineering, Architecture and Environment, Hubei University of Technology, Wuhan 430068, P. R. China.
| | - Longquan Chen
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou 313001, P. R. China. and School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
| | - Ying-Song Yu
- Department of Mechanics, School of Civil Engineering, Architecture and Environment, Hubei University of Technology, Wuhan 430068, P. R. China.
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43
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Du J, Wang X, Li Y, Min Q, Wu X. Analytical Consideration for the Maximum Spreading Factor of Liquid Droplet Impact on a Smooth Solid Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:7582-7590. [PMID: 34114824 DOI: 10.1021/acs.langmuir.1c01076] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Based on the energy conservation approach, this study develops a universal model to predict the maximum spreading factor of liquid droplet impact on a smooth solid surface. Validated with the present simulations and experiments in the literature, this model effectively overcomes the limitation of previous models in the viscous regime and greatly reduces the computing errors from over 30% to below 6%. It is demonstrated that the underestimated maximum spreading factor by previous models results from the overestimation of viscous dissipation. By replacing the conventional model of spreading time, tm = 8D0/3U0, with a more precise one, tm = 1.47τiWe-0.44, the formulation to compute the viscous dissipation of entire spreading is improved. Finally, we examine the applicability of present model in the capillary regime and good performance is also shown.
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Affiliation(s)
- 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
| | - 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, Tsinghua University, Beijing 100084, China
| | - 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
| | - 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
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44
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Charles CA, Louhichi A, Ramos L, Ligoure C. Viscoelasticity and elastocapillarity effects in the impact of drops on a repellent surface. SOFT MATTER 2021; 17:5829-5837. [PMID: 34037061 DOI: 10.1039/d1sm00438g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We investigate freely expanding viscoelastic sheets. The sheets are produced by the impact of drops on a quartz plate covered with a thin layer of liquid nitrogen that suppresses shear viscous dissipation as a result of the cold Leidenfrost effect. The time evolution of the sheet is simultaneously recorded from top and side views using high-speed cameras. The investigated viscoelastic fluids are Maxwell fluids, which are characterized by low elastic moduli, and relaxation times that vary over almost two orders of magnitude, thus giving access to a large spectrum of viscoelastic and elastocapillary effects. For the purposes of comparison, Newtonian fluids, with viscosity varying over three orders of magnitude, are also investigated. In this study, dmax, the maximal expansion of the sheets, and tmax the time to reach this maximal expansion from the time at impact, are measured as a function of the impact velocity. By using a generalized damped harmonic oscillator model, we rationalize the role of capillarity, bulk elasticity and viscous dissipation in the expansion dynamics of all investigated samples. In the model, the spring constant is a combination of the surface tension and the bulk dynamic elastic modulus. The time-varying damping coefficient is associated to biaxial extensional viscous dissipation and is proportional to the dynamic loss modulus. For all samples, we find that the model reproduces accurately the experimental data for dmax and tmax.
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Affiliation(s)
- Carole-Ann Charles
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France.
| | - Ameur Louhichi
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France.
| | - Laurence Ramos
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France.
| | - Christian Ligoure
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France.
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Hu Z, Zhang X, Gao S, Yuan Z, Lin Y, Chu F, Wu X. Axial spreading of droplet impact on ridged superhydrophobic surfaces. J Colloid Interface Sci 2021; 599:130-139. [PMID: 33933788 DOI: 10.1016/j.jcis.2021.04.078] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/16/2021] [Accepted: 04/16/2021] [Indexed: 12/17/2022]
Abstract
HYPOTHESIS Due to the complex hydrodynamics of droplet impact on ridged superhydrophobic surfaces, quantitative droplet spreading characteristics are unrevealed, limiting the practical applications of ridged superhydrophobic surfaces. During droplet impacting, the size ratio (the ratio of the ridge diameter to the droplet diameter) is an important factor that affects droplet spreading dynamics. EXPERIMENTS We fabricated ridged superhydrophobic surfaces with size ratios ranging from zero to one, and conduct water droplet impact experiments on these surfaces at varied Weber numbers. Aided by the numerical simulations and theoretical analysis, we illustrate the droplet spreading dynamics and reveal the law on the maximum axial spreading coefficient. FINDS The results show that the droplet spreading and retraction dynamics on ridged superhydrophobic surfaces are significantly asymmetric in the axial and spanwise directions. Focusing on the maximum axial spreading coefficient, we find it decreases first and then increases with increasing size ratios, indicating the existence of the critical size ratio. The maximum axial spreading coefficient can be reduced by 25-40% at the critical size ratio compared with that on flat surfaces. To predict the maximum axial spreading coefficient, two theoretical models are proposed respectively for size ratios smaller and larger than the critical size ratio.
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Affiliation(s)
- Zhifeng Hu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Xuan Zhang
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, 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, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Zhiping Yuan
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Yukai Lin
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
| | - Fuqiang Chu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China.
| | - Xiaomin Wu
- Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO(2) Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China.
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Understanding droplet collision with superhydrophobic-hydrophobic–hydrophilic hybrid surfaces. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126140] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Sompalli NK, Mohanty A, Mohan AM, Deivasigamani P. Visible-light harvesting innovative W 6+/Yb 3+/TiO 2 materials as a green methodology photocatalyst for the photodegradation of pharmaceutical pollutants. Photochem Photobiol Sci 2021; 20:401-420. [PMID: 33721273 DOI: 10.1007/s43630-021-00028-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/16/2021] [Indexed: 01/13/2023]
Abstract
In this work, we report on the synthesis of a new-age reusable visible-light photocatalyst using a heterojunction nanocomposite of W6+/Yb3+ on a mixed-phase mesoporous network of monolithic TiO2. The structural properties of the monolithic photocatalysts are characterized using p-XRD, SEM-EDAX, TEM-SAED, XPS, PLS, UV-Vis-DRS, FT-IR, micro-Raman, TG-DTA, and N2 isotherm analysis. The electron microscopic analysis reveals a mesoporous network of ordered worm-like monolithic design, with a polycrystalline mixed-phase (anatase/rutile) TiO2 composite, as indicated by diffraction studies. The UV-Vis-DRS analysis reveals a redshift in the light absorption characteristics of the mixed-phase TiO2 monolith as a function of W6+/Yb3+ co-doping. It is observed that the use of (8.0 mol%)W6+/0.4 (mole%)Yb3+ co-doped monolithic TiO2 photocatalyst, with an energy bandgap of 2.77 eV demonstrates superior visible-light photocatalysis, which corroborates with the PLS studies in terms of voluminous e-/h+ pair formation. The practical application of the photocatalyst has been investigated through a time-dependent dissipation of enrofloxacin, a widely employed antimicrobial drug, and its degradation pathway has been monitored by LC-MS-ESI and TOC analysis. The impact of physio-chemical parameters such as solution pH, sensitizers, drug concentration, dopant/codopant stoichiometry, catalyst quantity, and light intensity has been comprehensively studied to monitor the process efficiency.
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Affiliation(s)
- Naveen Kumar Sompalli
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology (VIT), Vellore Campus, Tamil Nadu, 632014, India
| | - Ankita Mohanty
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology (VIT), Vellore Campus, Tamil Nadu, 632014, India
| | - Akhila Maheswari Mohan
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology (VIT), Vellore Campus, Tamil Nadu, 632014, India
| | - Prabhakaran Deivasigamani
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology (VIT), Vellore Campus, Tamil Nadu, 632014, India.
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Fang WZ, Zhu F, Tao WQ, Yang C. How different freezing morphologies of impacting droplets form. J Colloid Interface Sci 2021; 584:403-410. [PMID: 33091865 DOI: 10.1016/j.jcis.2020.09.119] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 09/27/2020] [Accepted: 09/28/2020] [Indexed: 10/23/2022]
Abstract
HYPOTHESIS Freezing morphologies of impacting water droplets depend on the interaction between droplet spreading and solidification. The existing studies showed that the shape of frozen droplets mostly is of spherical cap with a singular tip, because of much shorter timescale of the droplet spreading than that of the solidification. Here, we create the experimental conditions of extended droplet spreading and greatly enhanced heat transfer for fast solidification, thereby allowing to study such droplet freezing process under the strong coupling of the droplet spreading and solidification. EXPERIMENTS We design experiments that a room-temperature water droplet impacts on a subcooled superhydrophilic surface in an enclosure chamber filled with nitrogen gas. We thoroughly investigate the freezing processes of impacting droplets under the effects of impact velocity and substrate temperature. Both the droplet impact dynamics and solidification are studied with a high-speed camera. FINDINGS We observed five different freezing morphologies which depend on the droplet impact velocity and substrate temperature. We found that the formation of diverse morphologies results from the competitive timescales related to droplet solidification and impact hydrodynamics. We also develop a phase diagram based on scaling analysis and show how freezing morphologies are controlled by droplet impact and freezing related timescales.
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Affiliation(s)
- Wen-Zhen Fang
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Fangqi Zhu
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Wen-Quan Tao
- Key Laboratory of Thermo-Fluid Science and Engineering, MOE, Xi'an Jiaotong University, Xi'an 710049, China
| | - Chun Yang
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore.
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