Electrically modulated droplet impingement onto hydrophilic and (super)hydrophobic solid surfaces

Abstract

Although the impact of impinging droplets on solid substrates has been widely studied, any possible non-trivial interaction between the substrate wettability and applied electric field toward altering the underlying dynamical characteristics remains unexplored. In this study, the interaction between electric field and hydrodynamic transport, toward influencing the dynamic behavior of a water droplet, dispersed in an immiscible fluid, on solid substrates has been numerically investigated. Finite element simulations were performed with a conservative level-set method to track the liquid-liquid interface. The numerical method is first validated with the available experimental data. After ensuring the accuracy of the simulation method, the effects of variations in impact velocity, electric field strength, electric permittivity of the surrounding liquid, and substrate wettability have been studied to clarify the underlying physics of this problem. These results may turn out to be of profound importance toward understanding the functionalities of various practical applications and manipulating the droplet dynamics through surface wettability-electric field interaction over the relevant spatiotemporal scales.

Electrohydrodynamics of dielectric droplet collision on different wettability surfaces

“…Although the field of droplet electrohydrodynamics was initiated almost more than fifty years ago [3,4], droplet impact studies in the presence of electric field are few and far between. Khojastech et al [24] performed numerical simulations of dielectric liquid droplet impact under the influence of electric field and reported that the droplet always deformed in the direction of the electric field. Ryu and Lee [25] showed experimentally that the maximum spreading diameter of a charged droplet on a dielectric substrate is more than an uncharged drop.…”

Understanding droplet collision with superhydrophobic-hydrophobic–hydrophilic hybrid surfaces

“…Modifying the wettability characteristics of a surface can control the movement and deflection of droplets (Nilsson & Rothstein, 2012), transport droplets without using external energy input (i.e. electric field) (Khojasteh et al, 2020) and avoid/promote formation of tiny satellite droplets (Mertaniemi et al, 2011). The methods for fabricating hydrophilic-superhydrophobic patterns were presented by Ueda and Levkin (Ueda & Levkin, 2013).…”

Free‐energy lattice Boltzmann simulations of slicing of rising droplets

“…By modifying this parameter, we can simulate different degrees of wettability of the cutting surface, from hydrophilic to hydrophobic properties. [ 37 ] …”