Spreading of triboelectrically charged granular matter

TL;DR

This study investigates how triboelectrically charged glass particles spread on a charged surface, revealing complex instabilities and pattern formations driven by time-dependent frictional interactions.

Contribution

It uncovers the dynamic pattern formation and instability mechanisms in charged granular spreading, linking macroscopic behaviors to triboelectric interactions.

Findings

Particles form a monolayer via sticking on the charged surface.

Instabilities lead to wave-like density modulations and particle jets.

Spreading front becomes homogeneous through lateral coalescence.

Abstract

We report on the spreading of triboelectrically charged glass particles on an oppositely charged surface of a plastic cylindrical container in the presence of a constant mechanical agitation. The particles spread via sticking, as a monolayer on the cylinder's surface. Continued agitation initiates a sequence of instabilities of this monolayer, which first forms periodic wavy-stripe-shaped transverse density modulation in the monolayer and then ejects narrow and long particle-jets from the tips of these stripes. These jets finally coalesce laterally to form a homogeneous spreading front that is layered along the spreading direction. These remarkable growth patterns are related to a time evolving frictional drag between the moving charged glass particles and the countercharges on the plastic container. The results provide insight into the multiscale time-dependent tribolelectric processes and motivates further investigation into the microscopic causes of these macroscopic dynamical instabilities and spatial structures.