Critical rolling angle of microparticles

Abstract

At the micrometer-scale and below, particle adhesion becomes particularly relevant as van der Waals force often dominates volume and surface proportional forces. The rolling resistance of microparticles and their critical rolling angles prior to the initiation of free-rolling and/or complete detachment are critical in numerous industrial processes and natural phenomenon involving particle adhesion and granular dynamics. The current work describes a non-contact measurement approach for determining the critical rolling angle of a single microparticle under the influence of a contact-point base-excitation generated by a transient displacement field of a prescribed surface acoustic wave pulse and reports the critical rolling angle data for a set of polystyrene latex microparticles.

Pre-rolling leaning of microparticles

“…1.d). Finally, the insitu determination of the average work-of-adhesion of the particles is conducted via the non-invasive ultrasonic excitation and laser interferometry sensing techniques developed previously [5,9,12,13,15] (Fig. 1.b).…”

“…The existence of elastic rolling resistance is now well established. A non-contact/non-invasive method for determining the CLA prior to freerolling has been reported recently [12].…”

“…When subjected to an external force/moment effect, the adhesion bond of a spherical particle on a flat elastic substrate creates both a restitution force (out-of-plane) and a moment resisting the outof-plane displacement and leaning/rocking (in-plane) angle of the particle, respectively [9]. Based on the Johnson-Kendall-Roberts (JKR) adhesion model [6] and as previously reported [12,13], the natural frequencies for the out-of-plane and rocking motions (f o and f r , respectively) of a spherical particle with a radius of R, mass density of  and the particle-substrate interface work-of-adhesion of W A are related by:…”

“…1.b). The acquired time series (waveforms) are subsequently saved in a personal computer for further spectral analysis to accurately measure and characterize the propagating SAW field on the substrate and to determine the adhesion characteristics of the particles by adopting previously reported methods[8][9][10][11][12].…”