Extended Data Fig. 7: Peak walking speeds on different textured surfaces.
From: Electronically integrated, mass-manufactured, microscopic robots
a, Schematics of the three surfaces robots walked on: hexagonal arrays of knobs spaced 5 μm apart and 10 μm apart, and random arrays of knobs. b, We measure the maximum lateral velocity a robot takes at each step, then aggregate the results into a distribution of peak speeds for each robot body type and frictional surface type (robot types are depicted in the inset images). The upper and lower error bars represent the upper and lower quartiles. Substantial variability is expected for walking on rough surfaces: each step can provide a different contact geometry and force. The order of magnitude is constrained by an interplay between friction and drag: the robot speed is bounded by the maximum frictional force the feet can generate. The maximum frictional force is found to be 0.1–0.3 of the robot’s weight, consistent with friction. (See Methods for a detailed discussion).
