Deformation and Adhesion of Elastomer Poly(dimethylsiloxane) Colloidal AFM Probes

We report on the synthesis and characterization of elastomer colloidal AFM probes. Poly(dimethylsiloxane) microparticles, obtained by water emulsification and cross-linking of viscous prepolymers, are glued to AFM cantilevers and used for contact mechanics investigations on smooth substrates: in detail loading-unloading cycles and adhesion forces are acquired on ion-sputtered mica, the deformation rate and dwell time being separately controlled. We discuss load-penetration curves and pull-off forces based on Zener and Maugis-Barquins models, accounting for adhesion hysteresis effects related to bulk creep, interfacial viscoelasticity and structural rearrangements at the polymer-substrate interface. A good agreement is found between experiments and theory, with a straightforward estimation of colloidal probes’ material parameters. We suggest the use of such probes for novel contact mechanics experiments involving fully elastic deformations at the sub-micrometer scale.