Adhesion of soft viscoelastic adhesives on periodic rough surfaces

We experimentally study adhesion of soft viscoelastic materials on surfaces with periodic roughness. The materials tested are partially crosslinked PDMS layers with a low shear elastic modulus (below 0.1 MPa) and variable viscoelasticity. We use an elastic surface instability to produce wrinkled PDMS surfaces. The hard periodic surfaces are then molded in Norland resin from the master surfaces. The periodic surface roughness is typically of the order of 100 microns. For identical surface roughness, we can use two surface topologies: peaks and holes. Using our model material and the model surfaces, we study in detail the interplay between the elastic penalties needed to conform the adhesive to the rough surface and the enhanced viscous dissipation during debonding. In this way we show, that adhesion on these surfaces can either be enhanced or decreased as a function of the surface topology and the viscoelastic properties of the material.