Adhesion Characterization Based on Rolling Resistance of Individual Microspheres on Substrates: Review of Recent Experimental Progress

Abstract

A review of the recent progress in mechanistic understanding and measurement of the micro-scale particle rolling resistance under the influence of adhesion and external excitations is presented. Two non-contact and one contact experimental approaches to measure the work of adhesion based on the rolling moment resistance of a particle are described. In the non-contact configurations, the microsphere is subjected to an external transient force field either by exciting the base of the surface to which the particle is adhered by a contact piezoelectric transducer or by exciting the particle and the substrate together by an air-coupled acoustic transducer. The vibration of the microsphere due to the excitation force field is measured by an interferometer in a non-contact manner. The natural frequency of the rocking motion of the microsphere is deduced from the measured transient waveforms. In the contact experiments, an atomic force microscope (AFM) tip is used to accurately push the particle with a controlled force in a chamber of a scanning electron microscope (SEM) to measure the rolling resistance of the particle prior to its rolling and sliding. The applied force is directly recorded and the displacement of the microsphere is determined by analyzing the SEM images of the rolling particle. The force–displacement curves are used for characterizing the work of adhesion of the microsphere–substrate bond. Experimental results using these three configurations are compared with the available data in the literature and good agreement between the theoretical predictions and the experimental values is reported.