Rolling resistance moment of microspheres on surfaces

Abstract

In the current work, for the first time, the existence of a rolling moment of resistance of an adhesion bond between a microsphere and flat surface subjected to external dynamic force has been experimentally demonstrated. The rotational motion of spherical particles deposited on a wafer is excited in the 0–3.5 MHz range using a piezoelectric transducer. The approach is based on (i) the observation that the contribution of the rotational (rocking) motion to the axial displacement of the particle are few orders of magnitude higher than those of the purely axial motion and (ii) the existence of a relationship between the rotational natural frequency of the adhesion bond and the work of adhesion. The natural frequency of the rotational (rocking) motion is extracted from the low frequency components of the transient response of the particle in the axial direction, which is measured by a laser interferometer. The existing theoretical adhesion models for rolling resistance moment are evaluated using the experimental results. Good agreement between the theoretical predictions and experimental values is found.

Acknowledgements

The authors acknowledge the National Science Foundation (Nanoscale Exploratory Research (NER) Program, Award ID 0210242), the New York State Science and Technology Foundation and the Center for Advanced Materials Processing (CAMP) at Clarkson University for their partial financial supports. The sputtered wafers with metal films utilized in the experiments were provided by Praxair/Electronics (Orangeburg, NY).