Toward generating low-friction nanoengineered surfaces with liquid-vapor interfaces.

Using molecular dynamics (MD), we investigate the importance of liquid-vapor interface topography in designing low-friction nanoengineered superhydrophobic surfaces. Shear flow is simulated on patterned surfaces. The relationship between the effective slip length and bubble meniscus curvature is attained by generating entrapped bubbles with large protrusion angles on patterned surfaces with nanoholes. We show that protruding bubbles can induce significant friction, which hinders the slip characteristics produced on liquid-vapor interfaces. By comparing surfaces with nanoholes and nanopillars, we also demonstrate that the continuity of the liquid-vapor interface can greatly influence slip. Our MD results yield an asymptotic behavior of slip length with varying gas fractions, which are found to be consistent with observations from simulations and analytical models produced in continuum studies.