Abstract
The unique self-repair function of slippery liquid-infused porous surfaces (SLIPS) exerts an important effect on maintaining the continuity and stability of lubricating film. In the self-repair process of SLIPS, the exudation of lubricant in the porous matrix is a common phenomenon. Meanwhile, the exudation behavior of lubricant in the pores is still unclear. This study established a numerical model for describing the exudation of oil droplet in micropore. The morphological evolution and flow characteristics were explored to reveal the flow mechanism of oil droplet spreading to oil film. Results show that the exudation process of lubricant on porous surface involves the rise of lubricant inside the pore, the generation, breaking and spreading of droplet on porous surface. During the rise of lubricant inside the pore, the internal pressure of the lubricant was negative. When the lubricant rose to the top edge of the pore, the contact line was pinned for the first time. And the Laplace pressure of the lubricant changed from negative to positive. Then the droplet generated and grew continuously on the porous surface. The contact line was pinned again until the droplet spread to the adjacent pore. As the apparent contact angle reached the maximum advancing angle, the droplet was depinning. Therefore, both pinning of the contact line occurred at the edge of the pore in the exudation process. Under the constant competition between the volume of droplet and the surface tension, the contact line was depinning, thus promoting the spread of the droplet into a film.
NSTL
Elsevier