The development of new types of soft robotic structures, and especially materials and methods for the fabrication of such robots, requires and offers rich new opportunities for collaborations involving organic chemistry, soft materials science, and robotics. This project centers on a methodology based on embedded pneumatic networks (EPNs) that enables large amplitude actuation in soft elastomers by pressurizing embedded channels.
Most robotic systems are hard, that is, composed of metallic structures with joints based on conventional bearings. Although hard robots capable of movement often possess limb-like structures similar to those of animals, more often, structures not found in nature – for example, wheels and treads – are used. Mobile elements of hard robots are often modeled on the limbs of animals or insects, and some locomotive systems (hexapods) use the passive compliance of air within pneumatic cylinders to move quickly on rough terrain.
The tentacles of squid, trunks of elephants, and tongues of lizards and mammals are such examples; there structures are muscular hydrostats. Squid and starfish are highly adept locomotors; their modes of movement have not been productively used in conventional hard robotics. These soft actuators rely on elastomeric structures and fibril arrangements of muscles that result in bending, elongation, or contraction without significant changes in the overall volume of the structure.
Our designs use networks of channels in elastomers that inflate like balloons for actuation (Figure 1). We decided to use a series of parallel chambers embedded in elastomers as a repeating component; stacking or connecting these components enables us to design and test prototype structures providing complex movements by intuition (empirically).
Complex motion requires only a single source of pressure and the movement can be designed by appropriate selection of the distribution, configuration, and size of the embedded pneumatic network. Using the techniques described here we have demonstrated a structure that can change its curvature from convex to concave, devices that act as compliant grippers for handling fragile objects (e.g., an uncooked chicken egg, a live mouse) without damaging either, various modes of locomotion and a flexible tentacle (Figure 2).