Abstract:

A plethora of applications in pharmacy, cosmetics, food industry and other areas are directly linked to the research fields of particle technology and contact mechanics. Here, a typical particle ensemble features particle sizes ranging from the nanometer up to the micrometer regime. Up to date, the direct access to particle motion and particle/surface interaction either requires dedicated homebuilt setups or is limited with respect to the weight of the particle and/or the accessible load regime. In the work presented here, a novel approach is introduced to overcome some of these limitations by using a nanoindentation setup. In addition to that, we demonstrate a relatively simple experimental path capable of probing sliding, rolling and torsional friction. Basically, the concept of the colloid probe technique, which is well established in the AFM community, is transferred to a nanoindenter setup. The potential of such strategy is shown by studying rolling friction of silica microspheres featuring radii of about 2.5µm, 10µm, 25 and 50µm on various substrates such as Si substrates featuring various roughness as well as flat gold films (300nm film thickness). Key aspects of this work include the influence of surface roughness, adhesion, humidity and the elastic/plastic transition on the rolling of particle over Si and gold surfaces.