Coalescence behavior and mechanism of autopoietic droplets on slippery liquid-infused porous surfaces (SLIPS)

•The coalescence process of droplets on SLIPS was researched.•Vortex ring was found in the liquid bridge area of the coalescence process.•The vorticity release of vortex ring leads to fluctuation of the liquid–gas interface.•Vortex ring promote coalescence and realize the self-repair of lubricating film.