Particles meet nanoindentation

The combination of an absence of simple, routine particle/surface interaction coupled with a lack of particle motion characterization techniques apt to examine a wide range of particle radii (measuring from hundredths of a µm down to some tens of nm) represents a challenge for many interlinked research areas, including colloid science and particle technology. To date, the direct study of particle motion and particle/surface interaction either calls for dedicated, homebuilt setups or is limited in terms of particle weight and/or accessible load regime. In order to overcome such limitations, this thesis presents a novel approach by introducing a nanoindentation-based setup. Here, the concept of the colloid probe technique, which is well established in the AFM community, is transferred to a nanoindenter platform. This allows for the handling of larger particles, higher load regimes and a unique strategy for sampling the rolling and torsional friction of individual particles. The feasibility of our concept is demonstrated through the examination of the sliding, rolling and torsional friction of silica microspheres with radii of about 2.5, 10 and 25µm on various substrates. The correlation between sliding, rolling and torsional friction with respect to opening angle of a Si-based rail system is evaluated and compared with various analytical predictions, contact models and particle simulations. Further, the experimental setup is extended to study adhesion force with a nanoindenter. In sum, the results presented here suggest that our concepts are promising tools for the field of particle technology, opening a route to direct study of key parameters of contact models which, in turn, renders the prediction of bulk behavior of fine powders possible.