The Influence of Surface Topography and Surface Chemistry on the Anti-Adhesive Performance of Nanoporous Monoliths

Abstract

We designed spongy monoliths allowing liquid delivery to their surfaces through continuous nanopore systems (mean pore diameter similar to 40 nm). These nanoporous monoliths were flat or patterned with microspherical structures a few tens of microns in diameter, and their surfaces consisted of aprotic polymer or of TiO2 coatings. Liquid may reduce adhesion forces F-Ad; possible reasons include screening of solid solid interactions and poroelastic effects. Softening-induced deformation of flat polymeric monoliths upon contact formation in the presence of liquids enhanced the work of separation W-Se. On flat TiO2-coated monoliths, W-Se, was smaller under wet conditions than under dry conditions, possibly because of liquid-induced screening of solid solid interactions. Under dry conditions; W-Se, is larger on flat TiO2-coated monoliths than on flat monoliths with a polymeric surface. However, under wet conditions, liquid-induced softening results in larger W-Se, on flat monoliths with a polymeric surface than On flat monoliths with an oxidic surface. Monolithic microsphere arrays show antiadhesive properties; F-Ad and W-Se, are reduced by at least 1 order of magnitude as compared to flat nanoporous counterparts. On nanoporous monolithic microsphere arrays, capillarity (W-Se is larger under wet than under dry conditions) and solid solid interactions (W-Se is larger on oxide than on polymer) dominate contact mechanics. Thus, the microsphere topography reduces the impact of softening-induced surface deformation and screening of solid solid interactions associated with liquid supply. Overall, simple modifications of surface topography and chemistry combined with delivery of liquid to the contact interface allow adjusting W-Se, and F-Ad Over at least 1 order of magnitude. Adhesion management with spongy monoliths exploiting deployment (or drainage) of interfacial liquids as well as, induction or prevention of liquid-induced softening,of the monoliths may pave the way for the design of artificial surfaces with tailored contact mechanics. Moreover, the results reported here may contribute to better understanding, of the contact mechanics of biological surfaces.