Controlling Adhesion with Surface Hole Patterns

Defined surface structures of various shapes and length scales can impact the adhesion of polymer interfaces. Most recent research has focused on the use of high-aspect-ratio post-like structures to modify the formation and separation mechanisms for a contacting interface. These mechanisms for controlling adhesion were inspired by the natural mechanisms present in examples such as the gecko and jumping spider. Although post-like structures are effective, numerous other geometries can impact adhesion properties through different mechanisms. In this article, we present and discuss the impact of surface hole patterns on the adhesion of soft, elastomeric interfaces. The surface holes are shallow, cylindrical depressions that decorate the surface of the elastomer and alter the separation mechanisms from rigid surfaces. We specifically focus on the effect of hole radius and nearest hole spacing on the overall adhesion descriptors. Using contact adhesion experiments largely based on the theory of Johnson, Kendall, and Roberts (JKR), we demonstrate that surface holes can alter the stability of the contact edge during interfacial separation. This stability does not affect the overall work of adhesion for a crosslinked polydimethylsiloxane interface, but it does permit tuning of the maximum separation force. These results emphasize the importance of measuring the interfacial area during adhesion testing, the significance of the contact edge, and the opportunities for using surface holes to tune the dissipative processes of interfaces that involve viscoelastic materials. These conclusions are particularly significant in the context of characterization techniques that do not allow for the direct measurement of contact area, such as nanoindentation or scanning probe microscopy measurements.