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Clemens BECHINGER - Université Stuttgart

Tribology of colloidal systems

Friction between solids is responsible for many phenomena like earthquakes, wear or crack propagation. Unlike macroscopic objects which only touch locally due to their surface roughness, spatially extended contacts form between atomically flat surfaces. They are described by the Frenkel-Kontorova (FK) model where a monolayer of interacting particles on a periodic substrate potential is considered. In addition to the well-known slip-stick motion the FK-model also predicts the formation of kinks and antikinks which largely reduce the friction between the monolayer and the substrate. Here, we report the direct observation of kinks and antikinks in a two-dimensional charge-stabilized colloidal crystal which is driven across different types of ordered substrates created by interfering laser beams. We show that the tribological properties only depend on the number and density of such excitations which propagate through the monolayer along the direction of the applied force. Finally, we also discuss, how positional order in a disordered colloidal system can be obtained by driving it across a quasiperiodic potential landscape.

[1] T. Bohlein, J. Mikhael, and C. Bechinger, Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces, Nature Materials 11, 126 (2012).

[2] T. Bohlein, and C. Bechinger, Experimental observation of directional locking and dynamical ordering of colloidal monolayers driven across quasiperiodic surfaces, Phys. Rev. Lett. 109, 058301 (2012).



Biographie :

Prof. Dr. Clemens Bechinger is a Max Planck Research Fellow at the MPI for Intelligent Systems, Stuttgart, and the head of the 2nd institute of physics at the university of Stuttgart. He graduated at the university of Konstanz and received several awards, including the Walter Schottky Prize for the investigation on structural properties and phase transitions with colloidal model systems. His research interest cover phase behavior of colloidal suspensions, quasicrystals, critical phenomena, microscopic thermodynamics, microfluidics, transport and flow through porous media, nanotribology, active Brownian motion.