Friction on the microscale.

A new method is presented for measurements of friction of microsized particles on surfaces. Specifically in this work, the particles are alumina with diameters between approximately 1 and 50 microm and the surfaces are InP, Si, and Cr. Friction is analyzed, its components are determined, and the friction coefficients are estimated from the experimental results. The technique and the specific instrument allow measurements of coefficients of friction for spherical particles with radii as small as 1 microm. For smaller sizes, the instrument needs to be modified by using a more powerful power supply, actuator with extended frequency and amplitude ranges, cooling of the actuator and the power supply, and the related mechanical modifications of the sample holder.