Water Droplets Translocation and Fission in a 3D Bi-Planar Multifurcated T-Junction Microchannels

Exploring the Role of Initial Droplet Position in Coalescence-Induced Droplet Jumping: Lattice Boltzmann Simulations

Coalescence-induced droplet jumping on superhydrophobic surfaces with different initial positions was numerically simulated using the 2D multi-relaxation-time (MRT) Lattice Boltzmann method (LBM). Simulation results show that for coalesced droplets with radii close to the structure length scale, the change of initial droplet positions leads to a significant deviation of jumping velocity and direction. By finely tuning the initial droplet positions on a flat-pillared surface, perpendicular jumping, oblique jumping, and non-jumping are successively observed on the same structured surface. Droplet morphologies and vector diagrams at different moments are considered. It is revealed that the asymmetric droplet detachment from the structured surface leads to the directional transport of liquid mass in the droplet and further results in the oblique jumping of the coalesced droplet. In order to eliminate the influence of initial droplet position on droplet jumping probability, a surface with pointed micropillars is designed. It is demonstrated that compared to flat-topped micropillars, a surface with pointed micropillars can suppress the initial droplet position effects and enhance droplet jumping probability. Furthermore, the effect of droplet/structure scale on droplet jumping is investigated. The influence of initial positions on coalescence-induced droplet jumping from the refined surface can be ignored when the droplet scale is larger than three times the structure scale. This study illustrates the role of initial droplet position in coalescence-induced droplet jumping and provides guidelines for the rational design of structured surfaces with enhanced droplet self-shedding for energy and heat transfer applications.

Splitting of droplet with different sizes inside a symmetric T-junction microchannel using an electric field

In the current study, droplets dynamics under an asymmetric electric field in a T-junction are numerically studied using COMSOL Multi-physics software. The effect of different factors such as dimensionless length of mother droplet (L^*), Capillary number (Ca), and electric capillary number (Ca_e) are investigated on the breakup process in symmetric T-junctions. Two novel patterns of droplets, namely, hybrid asymmetric splitting mode and sorting patterns, have been observed by imposing an electric field in one branch of the microchannel. It is also concluded that using an electric field is a promising strategy to reach droplets with arbitrary sizes and control over the splitting ratio of daughter droplets precisely in a T- junction by adjusting the electric field strength. After a certain electric capillary number (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left. {Ca_{e} } \right|_{Sorting}$$\end{document}CaeSorting), the mother droplet does not breakup and is sorted on the side of the branch that the electric field imposes. Furthermore, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left. {Ca_{e} } \right|_{Sorting}$$\end{document}CaeSorting increases with the increment of L^* and Ca.