Dynamic behavior of droplets on confined porous substrates: A many-body dissipative particle dynamics study

Abstract

Droplets wetting and impacting on porous substrates play a critical role in various printing processes and industrial applications. However, due to the lack of effective observation inside the pores, the dynamic behavior of the droplet is rather unclear. Here, we used a numerical method to investigate the dynamic behavior of droplets spreading on confined porous substrates with different surface fractions. The wetting process has been divided into two stages: the inertial stage and the viscous stage. The numerical results show a power-law evolution of the contact diameter with time, and the exponent has a linear relationship with the surface wettability. The scaling laws proved to have no dependence on the porosity. The presence of confined pores causes the spreading slower and makes the droplet reach an equilibrium state more easily. Then, the impacting process was reported by changing the initial velocities of the droplets. It was found that penetration is always observed after spreading. The wetting transition was captured, and the dimensionless maximum spreading was scaled. Finally, the coalescence-induced droplet jumping has been verified on confined porous substrates with a superhydrophobicity, suggesting the potential of porous structures in designing specific droplet behaviors.