MEASUREMENT OF PARTICLE ADHESION BY CENTRIFUGE MICROSCOPY

Leonard T. Demoranville, Greg Gillen, Robert A. Fletcher

Surface and Microanalysis Science Division, Material Measurement Laboratory, NIST

 The adhesion force of small particles to surfaces is important to several areas of study, and is of particular interest for the detection of trace explosives and drugs. Many studies of these forces employ atomic force microscopy (AFM), but such measurements require labor intensive commitment to acquire statistically relevant data.

This work explores the use of a centrifuge microscope based on an aerodynamically levitated spinning disc as a simple tool for quickly measuring particle adhesion force. An applied centrifugal force, produced by the spinning disc, dislodges particles when it exceeds the adhesion force. The particle’s trajectory is imaged and measured using an optical microscope and imaging software. The measured trajectory and rotational velocity are used to calculate the centrifugal force. By applying multiple particles to the same substrate, more statistically robust data sets can be produced quickly, when compared with AFM. This measurement approach has been tested using polystyrene latex (PSL) particles of various diameters on several substrates. The results presented suggest centrifuge microscopy is a useful tool for rapidly measuring the adhesion force of small particles.