Figure 4.

A schematic of the toe pad scrolling motion under DH, which is modelled as a rolling motion of a circle, with a radius r, along a horizontal plane. The trajectory (e.g. from point A to A′) follows the corresponding cycloid curve (e.g. blue-dashed line) depending on the particular location of each seta. Point B′ is the critical separation point of setae with respect to the substrate/wall, which determines the length of a peeling zone, L. θ* is the critical rotation angle that generates the cycloid curve from point B to B′. (Online version in colour.)