Meeting Abstract
Insect legs possess various structures that can enhance interaction with the substrate. We tested how effectively spines at the base of the tibia and foot pads on tarsi provide traction on various surfaces by measuring jump kinetic energy using high-speed video. We stimulated eight crickets, Gryllus firmus, to jump from glass, sand, sand paper, and Styrofoam to simulate smooth, granular, rough, and penetrable substrates. We compared control animals to those with disabled foot pads or disabled foot pads and spines. Both substrate and foot structure significantly affected jump kinetic energy. On glass, crickets performed typical leg extension, but friction pads only slipped. Sand reduced jump kinetic energy by 53% compared to sand paper due to yielding effects. Sand paper and Styrofoam resulted in similar performance. Disabling friction pads had no significant effect on jumping from these substrates. Spines increased jumping performance by 82% on Styrofoam, because they permitted penetration. Removing spines did not alter the kinetic energy on sandpaper or sand. Inspired by crickets, we tested the effect of spines and foot pads on a 2.5g insect-inspired jumping robot. Both substrate and foot structure significantly affected jump kinetic energy. Take off angle ranged between 30-40° and was unaffected by surface or foot structure. On smooth surfaces and sand, the robot only slipped. Jump kinetic energy on sandpaper was 43% greater than on Styrofoam, but adding spines increased penetration and jump kinetic energy by 65%, doubling jump distance to 40cm. Adding rubber foot pads allowed the robot to jump on smooth surfaces. Leg spines appear critical for maximum jumping performance on surfaces that allow penetration and foot pads can increase performance on smooth surfaces. Jumping robots can also serve as physical models to generate new hypotheses for jumping animals.
