la700408v_si_003.doc (327 kB)
Quantitative Measurement of Friction between Single Microspheres by Friction Force Microscopy
journal contribution
posted on 2007-07-31, 00:00 authored by Xing Ling, Hans-Jürgen Butt, Michael KapplThe sliding friction between single silica microspheres was examined by applying friction force microscopy to probe
the interaction between spherical silica particles glued to a tipless atomic force microscopy (AFM) cantilever and
another particle glued to a glass slide. A three-dimensional model handling the complex contact geometry between
spherical particles was established to compute friction and normal forces at the sliding interface from measured
deflections of the AFM cantilever. Results obtained at different loads show a linear relationship between friction and
normal force, with a friction coefficient of 0.4 between silica spheres. Friction in this system occurs at multi-asperity
contacts. The results show that the macroscopic friction law of Amontons can be used to model the friction behavior
of micrometer-sized granular matter. For plasma-treated silica particles, increased friction as well as wear could be
observed during sliding.