| AVS 60th International Symposium and Exhibition | |
| Tribology Focus Topic | Monday Sessions |
| Session TR+AS+NS+SS-MoA |
| Session: | Molecular Origins of Friction |
| Presenter: | P.V. Antonov, Leiden University, Netherlands |
| Authors: | P.V. Antonov, Leiden University, Netherlands J.W.M. Frenken, Leiden University, Netherlands |
| Correspondent: | Click to Email |
We report the first stages of an experiment to lower dry, unlubricated friction by use of a tailor-made nanostructure. In previous studies, we have demonstrated that random thermal fluctuations change the familiar, atomic stick-slip motion of the tip of a friction force microscope (FFM) into a thermal drifting motion, when these fluctuations are strong enough with respect to the barriers in the energy landscape. Based on a two-mass-two-spring model of an FFM [1], we know that these excitations are concentrated in the last nanometers of the tip, because of its extremely small mass and its flexibility. To achieve similar behavior in a macroscopic contact with an area well beyond that of the very specific tip-surface geometry of an FFM, we have shaped one of the two, macroscopic contacting surfaces in the form of a micro-fabricated array of Si nanopillars, each with a well-defined spring coefficient, equal to that of a standard FFM tip. This pattern can be regarded as a large multitude of FFM-like tips, each one exhibiting the thermal fluctuation motion that we identified as a lubricating effect in an FFM. Since the density of these asperities is high, the forces on each individual asperity are always low enough to keep its deformations completely elastic. We expect that each of the tip-like pillars will fluctuate independently under the load of a ball-shaped AFM tip and as a result of this, it should be possible to translate the entire, multi-asperity contact by an extremely low lateral force. This approach should lead not only to low friction, but also to a characteristic, strong dependence of the sliding motion and the friction force on temperature and on sliding velocity. We will also explore how the thermal fluctuation behavior changes as a function of the dynamic properties of the individual nanopillars and how it evolves when we scale up the total number of asperities that are simultaneously in contact.
[1] S.Yu. Krylov, J.W.M. Frenken, Phys. Rev. B80, 235435 (2009).