(689c) Load-Induced Hydrodynamic Lubrication of Porous Polymer Films

In this study, we explore the mechanisms involved in the lubrication of porous polymer-based surfaces or coatings with ultra-low coefficients of friction arising from the partial hydrodynamic repulsive forces acting between shearing solid yet compliant surfaces.  Through tribological experiments, using a universal materials tester, we show how it is possible to shift the lubrication regime from boundary lubrication to hydrodynamic lubrication even at relatively low shearing velocities.  We hypothesize that the extruding liquid from the pores provides a repulsive hydrodynamic force, which aids in minimizing contact between the shearing surfaces. Conventional phololithography and molding techniques are used to fabricate the porous polydimethyl siloxane (PDMS) surfaces.   Specifically, the effect of the pore density and pore size on the lubrication properties will be elucidated.  In addition, the effect of the lubricating liquid (including water and an aqueous sodium dodecylsulfate solution) on the friction forces will be studied.  Potential applications for these low friction biocompatible surfaces include their use in the fabrication of joint implants.