A Small Steerable Tip Based on Dielectric Elastomer Actuators

Soft robotics has sought to emulate natural behaviors. One impressive ability of living systems is operating in confined and narrow pathways, from caterpillars to tapeworms. Among the soft actuators, dielectric elastomer actuators (DEAs) are suitable candidates for this ability with fully soft systems, energy, and power densities on par with natural muscles and simple electro-mechanical drive. In this letter, we present the systematic guideline for designing and fabricating a steerable tip based on bimorph DEAs capable of guiding a small flexible insertion tube. We developed the tip by assembling identical DEAs into a multilayer structure, which induces stable bending at the same bias voltage. We investigated various structural parameters such as length, passive zone, and multilayer/scaling effect for active and smooth navigation. Then, we suggested the methodology to provide the tip with not only flexibility to move along with pathways but also sufficient stiffness to lead the flexible tube attached to the tip in the desired direction. The tip's steerable performance was analyzed in various conditions, such as deflected by gravity or suspended in liquid media of various viscosities and conductivities. We demonstrated fast, reliable actuation with active tip control and the ability of shaking or stirring functions based on dynamic actuation.