Movie 4. Snake-like motion on a surface with scales of varying lateral orientation. The motion of a thin hydrogel filament on a thin elastic polydimethylsiloxane film subject to harmonic lateral vibrations is shown. (The substrate is always vibrated sinusoidally, except when otherwise mentioned.) Many "scales" are scored on the elastic layer, with periodically varying orientations. Frequency, 100 Hz; displacement amplitude, 0.27 mm; filament length, 5.5 cm; filament radius, 1 mm.