When Particles Meet Nanoindentation: A Novel Strategy for Studying Particle Motion and Particle/Surface Interaction

Abstract

ABSTRACTA 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. In this context we introduce a nanoindentation based approach capable of probing mechanical interaction of micron-sized particles. Basically, the concept of the colloid probe technique, which is well established in the AFM community, is transferred to a nanoindenter. In particular, this setup allows addressing limitations, which are typically associated with AFM based techniques, such as particle weight and accessible load regime. Additionally, we will show the versatility of this approach by presenting simple experimental paths capable of probing sliding, rolling and torsional friction. The potential of such setting is shown by studying rolling friction of silica microspheres featuring radii of about 2.5µm, 10µm, 25 and 50µm in contact with various substrates, respectively. Substrates utilized within the framework of this study are Si surfaces featuring various roughness as well as flat gold films (300nm film thickness). Key aspects of this work include the influence of surface roughness, adhesion force, humidity and the elastic/plastic transition on the rolling contact of the corresponding particles.