Frequency Controlled Bidirectional Ratcheting Biomimetic Motion

This paper describes a frequency controlled bidirectional ratcheting biomimetic motion of a cylindrical soft body similar to the motion of limbless creatures such as worms and some insects. Using a laterally vibrating shaker table, we achieved a bidirectional motion by simply attached two polydimethylsiloxane (PDMS) rods with opposing saw-tooth shaped legs. These two parts have different ratchet density and leg height. The polymeric body was floating on a thin silicone lubricating oil 20 μm in thickness. While vibrated at a constant amplitude of 0.2 mm, the micromobile soft cylinder (2x2x20 mm³in dimensions) changed its motion direction at a cross-over frequency of 156 Hz. This cross-over phenomena is due to difference between the static and kinetic friction of the two opposing parts.