Caterpillars are excellent and sure (pseudo)footed climbers. Caterpillars have special extensions of the abdomen for gripping plants called prolegs. At the tip of the proleg are rows of small hooks called crochets. The crochets will tightly grip a surface. A caterpillar clinging to your finger must be pried off, similar to separating velcro strips.The prolegs of the caterpillar are powered by well studied muscles, the planta retractor muscles. When a planta retractor muscle contracts, the proleg is lifted off the plant. In the retracted position the proleg hovers in the air off the plant and is easily moved. The caterpillar swings its leg forward through the air. After the movement is complete, the retractor muscle relaxes and the proleg returns to the plant, with crochets extended to grip the plant. The crochets grip the plant much the same way that a cat’s claws will grip your hand. However, the crochets are far smaller than the claws of a cat and do not penetrate deep into the plan (or penetrate your skin the way a larger cat’s claw might).
The grip of the caterpillar crochet is the bio-inspiration for a “Compliant Gripper” for use by a robot. The Compliant Gripper is currently under development by the Seoul National University Biorobotics Laboratory. The gripper uses the same principles of the caterpillar crochet. The gripper features sharp metal pins that will grip the object. The pins are mounted on a structure with shape memory alloy coil actuators and sides that can buckle under pressure. The buckling enables the “crochets” of the gripper to engage the surface. The gripper is demonstrated in the video below and is capable of lifting a small brick.