  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.
