Poly(dimethylsiloxane) colloidal AFM probes: a new tool for mescoscale contact mechanics investigations

We report on contact mechanics experiments performed by means of elastomer colloidal Atomic Force Microscopy probes. Poly(dimethylsiloxane) microparticles, obtained by water emulsification and cross-linking of viscous prepolymers, are glued to AFM cantilevers and pressed against elastically stiff substrates. Load-penetration curves show a remarkable dependence on bulk and interfacial materials' properties, namely viscoelasticity, interface energy and surface roughness. We suggest the use of such probes for novel contact mechanics experiments involving fully reversible deformations at the sub-micrometer scale; as an example we demonstrate the capability to appreciate significant variations of contact stiffness for rough PDMS/SrTiO3 contacts.