Cassie-Wenzel–like transition in patterned soft elastomer adhesive contacts

Laboratoire de physique des solides, Université Paris-Sud - CNRS, 91405 Orsay cedex, France, EU

Received: 3 October 2012
Accepted: 11 December 2012

Abstract

We present an experimental and theoretical analysis of the transition from top to mixed top and full contacts between a smooth elastomer sphere and an elastomer substrate micropatterned with hexagonal arrays of cylindrical pillars. We show that surprisingly the overall behavior of the apparent radius of contact vs. the applied load obeys JKR contact mechanics, whatever the nature of the contact (top or mixed). This allows us to propose a mechanical description predicting quantitatively the evolution of the critical load for the onset of full contact with the pattern geometry and qualitatively that of the area of full contact above this threshold. We emphasize the role of the mechanical coupling between the pillars induced by the deformation of the substrate for large enough densities of pillars.