(159f) Effect of Surface Geometry on the Frictional Properties of Soft Substrates

Lubricated friction on soft micropatterned surfaces are of significant interests due to their wide existence in nature and our daily lives. We design soft poly(dimethyl siloxane) (PDMS) substrates with controlled dimensions and spacings to study the influence of surface geometry on their frictional and lubrication properties. The 3D structures of micropatterns alters the solid deformation and fluid dissipation during elastohydrodynamic lubrication (EHL) friction. To fully understand the effect of surface geometry on EHL friction, we investigated effect of pattern length, spacing and height on the EHL friction individually. Tribological tests performed with a thin layer of aqueous glycerol solution between the PDMS substrates show that the frictional behavior does not follow the type of Stribeck curve that is typically observed with flat surfaces. This major difference can be explained by a scaling theory we developed, in which the friction force and the normal force are expressed with a combination of lubricant properties, experimental conditions and surface geometries. Our study establishes a design framework for the friction of elastomers based on their surface micropatterns, and paves the way for engineering soft materials in technological applications such as wearable electronics, antifouling coatings, and synthetic implants.