Article
Chemistry, Physical
Bo Hou, Chunya Wu, Xiguang Li, Junjie Huang, Mingjun Chen
Summary: This study analyzed the forces and critical conditions on static sessile droplets deposited on hydrophobic micropillar-structured surfaces, proposing a new force-balance model which showed better agreement with experimental results compared to classical models. Integration of depinning mechanisms into the model allows for reliable estimations of critical conditions for the C-W transition during evaporation, providing appropriate geometric parameters for achieving high hydrophobic stability.
APPLIED SURFACE SCIENCE
(2021)
Article
Energy & Fuels
Sergey Misyura, Andrey Semenov, Yulia Peschenyuk, Ivan Vozhakov, Vladimir Morozov
Summary: In recent years, miniaturization of electronic devices has led to the need for new cooling systems. The use of a surfactant has been found to increase droplet diameter and evaporation rate. Despite extensive research in this area, there are still unanswered questions regarding the influence of surfactant and wall temperature on evaporation rate.
Article
Thermodynamics
Seung Ho Yeom, Kyeong Ho Jang, Hyung Ju Lee, Chang Kyoung Choi, Seong Hyuk Lee
Summary: The evaporative characteristics of ethylene glycol-water binary mixture droplets (EGWBMDs) were studied, and it was found that the droplets evaporated in the depinning mode following the constant contact radius mode. The concentration of ethylene glycol increased with time, indicating selective evaporation. The volume variation of EGWBMDs showed a non-linear change due to the different volatility of each component. The evaporation rates of water and ethylene glycol were calculated based on concentration and shape measurements, and were found to be consistent with predictions obtained using a diffusion model, with maximum and average error rates of 6.14% and 2.56%, respectively.
APPLIED THERMAL ENGINEERING
(2023)
Article
Polymer Science
Bin Cheng, Haitong Zhao, Jingfa Yang, Jiang Zhao
Summary: Continuous monitoring of the re-entrant phase separation inside evaporating droplets of PNIPAM solution with ethanol and water binary solvent was conducted using optical microscopy. The higher evaporation rate of ethanol led to changes in solvent composition, causing the polymer to precipitate and redissolve due to cononsolvency. Direct observation revealed that phase separation occurred at the air-liquid interface and the precipitates were brought into the droplet by circulations induced by Marangoni flow, providing a new method of mass transportation during phase separation.
Article
Chemistry, Physical
Gannena K. S. Raghuram, Lalit Bansal, Saptarshi Basu, Aloke Kumar
Summary: This study experimentally investigates the concentration and molecular weight dependence of deposit patterns of polymer droplets on hydrophobic surfaces. The results show a transition from ring to non-ring patterns with increasing concentration, while decreasing the polymer molecular weight does not suppress the coffee ring formation. The findings provide insights for applications like inkjet printing, surface coatings, and biotechnology assays where tuning polymer deposit patterns is important.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2021)
Article
Multidisciplinary Sciences
Rachid Bennacer, Xiaoyan Ma
Summary: Research on droplet evaporation has various applications and the mechanisms of droplet evaporation have been researched for decades. This study analyzes the effects of surfactant and temperature on the evaporation rate and mechanisms. The evaporation is influenced by the dynamics of droplet spreading ability and the depinning event. It is complex to predict the evaporation due to continuous changes in surfactant concentration. Temperature change modifies surface tension and induced inner flows. The depinning force with surfactant was quantified, and a constant force was found. The evaporation rate shows a classical decrease after depinning and, in the case of surfactant, an enhancement appears at a later droplet lifetime. Local evaporation does not change significantly with respect to surfactant concentration.
Article
Multidisciplinary Sciences
Hossein Zargartalebi, S. Hossein Hejazi, Amir Sanati-Nezhad
Summary: The authors introduce a passive protocol to suppress the coffee-ring effect and form uniform films at micro- and nanoscales by combining superhydrophilic substrate with a neutral-wetting low-roughness mold. This method has broad applications in fabricating ordered coatings, producing nanofilters, and creating functionalized nanosensors.
NATURE COMMUNICATIONS
(2022)
Article
Mathematics, Applied
Hyun Geun Lee, Junxiang Yang, Sangkwon Kim, Junseok Kim
Summary: This paper presents a mathematical model and numerical scheme for droplet evaporation, using a Cahn-Hilliard equation with an interfacial evaporation mass flux term. The study shows that the dynamics of evaporation are influenced by the contact angle on a solid substrate.
APPLIED MATHEMATICS AND COMPUTATION
(2021)
Article
Thermodynamics
Guo-Hao Li, Xiao-Ye Yang, Xianfu Huang, Ying-Song Yu
Summary: The wettability and evaporation behavior of dilute sodium dodecyl sulfate (SDS) droplets on micropillar-arrayed poly-dimethylsiloxane (PDMS) surface were experimentally investigated. It was found that the contact angles of the droplets decreased with increasing initial SDS concentration, and the wettability depended on both the SDS concentration and surface roughness. The evaporation process started with a constant contact radius (CCR) mode due to the adhesion between the droplets and the micropillars. Interestingly, short-time spontaneous spreading was observed during the evaporation of dilute SDS droplets on sparser micropillar patterns, which could be attributed to the transition from Cassie-Baxter wetting state to Wenzel wetting state.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Chemistry, Physical
A. W. Zaibudeen, Ranjini Bandyopadhyay
Summary: This study investigates the correlation between the evaporation dynamics of a gold nanorod dispersion droplet and the formation of a coffee stain with distinct microstructures. The droplet retraction, pinning, and quick evaporation during different drying phases are found to be clearly correlated with the aggregation regions in the coffee stain. The unique assemblies of gold nanorods in the coffee stain edge have the potential to be used for plasmonic sensors, while the large clusters of nanorods outside the stain could enhance the fluorescence of low quantum yield molecules. Controlling the evaporating droplet kinetics can tailor the solute deposition pattern.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2022)
Article
Chemistry, Physical
Xiao-Ye Yang, Guo-Hao Li, Xianfu Huang, Ying-Song Yu
Summary: The wetting behavior of aqueous SDS droplets on PDMS surfaces was studied, and it was found that substrate elasticity and initial SDS concentration have an influence on the wetting behavior. A physical mechanism was proposed to explain the phenomena.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2023)
Article
Mechanics
Xiaolong Zhang, Vadim S. Nikolayev
Summary: This paper presents a theoretical analysis of the liquid film dynamics during the oscillation of a meniscus in a cylindrical capillary, considering factors such as dynamic profile, finite film length, pinned contact line, and contact angle variations. The study also explores the average film thickness as a function of system parameters and compares numerical results with experimental data and quasi-steady approximation. Additionally, the paper discusses the effects of superheating on the oscillating meniscus process and the possibility of contact line recession due to evaporation.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Multidisciplinary
Wenxiang Wu, Jiankui Chen, Wei Chen, Zhouping Yin
Summary: Inkjet printing is a promising manufacturing technology for OLED displays due to its high material utilization, low cost, and large-area production advantages. However, the evaporation of droplets in micron-size pixel pits is difficult to control, leading to defects like the coffee ring. This study establishes a multiphase thermal lattice Boltzmann (LB) model to investigate the evaporation process of droplets in pits and explores the effects of pit height and contact angle on the evaporation mode. The revealed evaporation mechanism can help regulate droplet behavior and control the cured film shape in the OLED printing process.
Article
Thermodynamics
Dongmin Wang, Ping Cheng
Summary: This paper compares the stability of three commonly used contact angle algorithms in pseudopotential lattice Boltzmann models under non-isothermal conditions. It is found that adding a special ghost fluid layer can improve the numerical stability and accurate prediction of droplet interface shapes and Marangoni vortex shapes near the triple-phase contact line.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Engineering, Multidisciplinary
Junxiang Yang
Summary: In this study, novel models based on phase field method were developed to investigate the evaporation of single droplets and multiple droplets on a substrate. The interface of droplets was implicitly captured and the contact angle boundary condition was used to reflect different wetting conditions. An evaporation term was derived to account for the effect of evaporation, and an efficient algorithm was implemented. The proposed models and algorithms were validated by comparing with analytical results, and the evaporation of multiple droplets under different conditions was simulated.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
