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 cyclic loading-unloading experiments
are carried on ion-sputtered mica, the deformation rate and dwell time being separately controlled. We analyze
load-penetration curves and pull-off forces with models due respectively to Zener, Maugis and Barquins, and Greenwood
and Johnson and account for 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 reversible deformations at the submicrometer scale.