On the Nature of the Friction between Nonstick Droplets and Solid Substrates

The lateral rolling of nonstick water and glycerol droplets deposited on solid substrates inclined at the sliding angles was studied. Droplets deposited on lotuslike water-repellent surfaces and liquid marbles (powder-coated droplets) deposited on solid substrates demonstrated similar behavior. The motion of both droplets and marbles featured friction that is far from Amonton type. The sliding angles of nonstick drops are sensitive to the "history" of a drop on the substrate. The friction of glycerol marbles is governed by viscous dissipation, whereas the rolling of water marbles is dictated by adhesion forces acting within the contact area.