Biomedical subjects

R Bennewitz

Publications and source records attributed to R Bennewitz.

4 recordsLinked to original sources

PubMed2004

Transition from stick-slip to continuous sliding in atomic friction: entering a new regime of ultralow friction.

A transition from stick-slip to continuous sliding is observed for atomically modulated friction by means of a friction force microscope. When the stick-slip instabilities cease to exist, a new regime of ultralow friction is encountered. The transition is described in the framework of the Tomlinson model using a parameter eta which relates the strength of the lateral atomic surface potential and the stiffness of the contact under study. Experimentally, this parameter can be tuned by varying the normal load on the contact. We compare our results to a recently discussed concept called superlubricity.

Journal Article↗

PubMed2003

Interaction potential and hopping dynamics governing sliding friction.

The friction force on a nanometer-sized tip sliding on a surface is related to the thermally activated hopping of the contact atoms on an effective atomic interaction potential. A general analytical expression relates the height of this potential and the hopping attempt frequency to measurements of the velocity dependence of the friction force performed with an atomic force microscope. While the height of the potential is roughly proportional to the normal load, the attempt frequency falls in the range of mechanical eigenfrequencies of the probing tip in contact with the surface.

Journal Article↗

PubMed2002

Abrasive wear on the atomic scale.

A scanning force microscope in ultrahigh vacuum has been used to realize and detect atomic-scale abrasion on KBr(001). The continuous time evolution of the lateral force under scratching reveals that the wear mechanism is due to the removal and the rearrangement of single ion pairs. The debris is reorganized in regular terraces with the same periodicity and orientation as the unscratched surface, as in local epitaxial growth. The applied load has a strong influence on the abrasive process, whereas the scan velocity is less relevant.

Journal Article↗

PubMed2000

Velocity dependence of atomic friction

Sliding friction between the tip of a friction force microscope and NaCl(100) was studied to deduce the velocity dependence of friction forces on the atomic scale. A logarithmic dependence of the mean friction force is revealed at low velocities. The experimental data are interpreted in terms of a modified Tomlinson model which is based on reaction rate theory.

Journal Article↗