Droplet wettability and repellency on fluorinated lubricant-infused surfaces: A molecular dynamics study

Fluorinated lubricant-infused surfaces are gaining remarkable attention as a promising candidate of self-cleaning and antifouling materials and liquid-resistant surface coatings. Despite all the lubricant-infused surfaces are related to a surface lubrication stabilized in a porous or nanotextured solid, they may present varying droplet morphologies regarding to the state of cloaking, lubricant ridges, and the wetting state. In this work, molecular dynamics simulations were performed to investigate the droplet wettability and repellency on fluorinated lubricant-infused surfaces. A phase diagram of possible droplet configurations at static equilibration has been developed and compared with theoretical predictions by examining the effects of interfacial tensions and lubricant thickness comprehensively. The static and dynamic droplet repellencies were further quantified in terms of the static, advancing, and receding contact angles and the shedding velocity. In particular, the distinctive “slippery Cassie” surface could effectively conquer the droplet pinning instability by energetically favorably “slippery Wenzel-to-Cassie” transition as well as self-replenishing of lubricant, as compared to the superhydrophobic surface that is susceptible to the irreversible transition to Wenzel state. The findings in this work are believed to provide molecular scale understanding and intuitive guidelines for inspiring applications of fluorinated lubricant-infused surfaces by designing surface wettability and lubricant thickness level rationally.