Probing and tuning frictional aging at the nanoscale.

Time-dependent increase of frictional strength, or frictional aging, is a widely observed phenomenon both at macro and nanoscales. The frictional aging at the nanoscale may result from nucleation of capillary bridges and strengthening of chemical bonding, and it imposes serious constraints and limitations on the performance and lifetime of micro- and nanomachines. Here, by analytical model and numerical simulations, we investigate the effect of inplane oscillations on friction in nanoscale contacts which exhibit aging. We demonstrate that adding a low amplitude oscillatory component to the pulling force, when applied at the right frequency, can significantly suppress aging processes and thereby reduce friction. The results obtained show that frictional measurements performed in this mode can provide significant information on the mechanism of frictional aging and stiffness of interfacial contacts.