Dynamics of drops on hygroscopic ionic liquid aqueous solution-wetted porous surfaces

Abstract

The impact dynamics of water drops on porous surfaces wetted by a hygroscopic ionic liquid aqueous solution are investigated. Firstly, to better illustrate the different dynamic characteristics of water drops on ionic liquid-wetted porous surfaces, it is compared with that on the dry and water-wetted porous surfaces. The results indicate that, the water drop barely penetrates on the dry porous surface at ambient temperature, but penetrate when the surface temperature is raised or the surface is pre-wetted. The maximum spreading and penetration of the droplet on the ionic liquid-wetted surface is larger and faster than that on the water-wetted surface. Then, the effect of the mass fraction of aqueous ionic liquid, impact velocity, porosity on the spreading and penetration is explored. The larger the mass fraction of aqueous ionic liquid on the porous surface, the faster the droplet spreading factor, height, and residual volume decrease. The effect of impact velocity is even more pronounced for the water droplets impacting on pure ionic liquid-wetted porous surfaces. A higher porosity contributes to a smaller spreading diameter but a larger volume decreasing rate on the wetted porous surface.