Tailored slip length: Investigating the effect of solid–liquid interfacial tension

By inducing non-zero fluid velocity on the surface wall, energy loss due to drag can be reduced due to slipperiness. The slippage due to molecular interactions is insignificant for most larger-scale applications. However, the presence of gas can potentially induce larger slippage that is related to solid–liquid interfacial tension. In the current work, we studied the influence of surface solid fraction (ϕs) and contact angle (θs) on slip length over micro-patterned surfaces. The surfaces have pillars with different ϕs fabricated by CO2 laser. The micro-pillars entrap air in between the structures, i.e., plastrons. The θs influences presence of additional gas over the solid surface due to interfacial tension. The slip length was calculated from shear stress measurements of the rheometer. The results show that the slip length dependence on ϕs follows the literature model for one-dimensional (1D) longitudinal grates (LG). Furthermore, a linear dependence of slip length on the cos(θs) was found, which has not been explored before for micro-patterned surfaces. Comparing experiment results with the predicted slip length shows an error of 6.9% (current correlation). The present study discusses the importance of surface's intrinsic energy on slip length for structured surfaces.