Characteristics of droplet exudation on slippery liquid-infused porous surfaces considering thermal effect

Abstract

The self-healing property of slippery liquid-infused porous surfaces ensures the continuity and stability of the liquid film on the surfaces. Therefore, how to promote the exudation and spreading of the lubricant is the key to realize the self-healing. In this study, a numerical model of lubricant exudation and spreading in micropores was established under the stimulation of the external temperature field. The morphological evolution of the meniscus and the distribution characteristics of the internal pressure during the exudation process were investigated. The influence mechanism of the thermal effect on the exudation and film formation on the porous surface was revealed. Results show that the formation process of lubricating film includes the lubricant exudation in the pores, the growth and spreading of microdroplets on the porous surface. In the lubricant exudation stage, the internal pressure of the fluid is negative. When the lubricant exudes to the edge of the pore, the internal pressure of the liquid changes from negative to positive. The three-phase contact wire is pinned at the edge of the pore and droplets are formed on the porous surface. When the droplet begins to spread, the internal pressure of the droplet decreases for the increasing of the meniscus curvature radius. The spreading velocity decreases gradually in the form of fluctuation under the combined action of the time-varying resistance and driving force. At higher wall temperature, the droplet surface tension and viscous resistance decrease, whereas the thermal-capillary force and driving force increase. Therefore, the higher the wall temperature, the greater the average velocity of the droplet spreading front, and the better the droplet spreading performance. Therefore, higher wall temperature can promote the droplet exudation and spreading on the surface, which is conducive to the self-healing of the lubricating film.