New Perspectives of Microtribology - Methods and Applications

We have developed a strategy to investigate thin film lubricants commonly used for computer hard disks employing Friction Force Microscopy (FFM). Polyflouropolyether (PFPE) lubricant films of different thickness were measured. Depending on the probe radius and film thickness, we obtain different friction coefficients indicating altered friction mechanisms. Extending the FFM to ultrasonic frequencies, we can obtain friction maps revealing additional material contrast. Furthermore, we present a new approach for studying friction and the stick-slip phenomenon using torsional resonances of FFM cantilever. This ultrasonic friction mode allows us to analyze the load and velocity dependence of friction characterizing the resonance modes of the SPM cantilever. With respect to micromechanical parts, the use ultrasonic vibrations can reduce dry friction. Mechanically vibrating a silicon wafer sample in- or out-of-plane, at ultrasonic frequencies, can substantially decrease the friction force measured by microscopic and macroscopic methods.