Monolithic Polymer Nanoridges with Programmable Wetting Transitions

Abstract

This paper describes polymeric nanostructures with dynamically tunable wetting properties. Centimeter-scale areas of monolithic nanoridges can be generated by strain relief of thermoplastic polyolefin films with fluoropolymer skin layers. Changing the amount of strain results in polyolefin ridges with aspect ratios greater than four with controlled feature densities. Surface chemistry and topography are demonstrated to be able to be tailored by SF₆ -plasma etching to access multiple wetting states: Wenzel, Cassie-Baxter, and Cassie-impregnating states. Reversible transitions among the wetting states can be realized in a programmable manner by cyclic stretching and reshrinking the patterned substrates without delamination and cracking.

Keywords: Cassie-Baxter state; Cassie-impregnating state; Wenzel state; nanoridges; polyolefins; wetting transitions.