High-Speed, Helical and Self-Coiled Dielectric Polymer Actuator

Abstract

Novel actuator materials are necessary to advance the field of soft robotics. However, since current solutions are limited in terms of strain, strain rate, or robustness, a new actuator type was developed. In its basic configuration, this actuator consisted of four layers and self-coiled into a helix after pre-stretching. The actuator principle was a dielectric polymer actuator. Instead of an elastomer, a thin thermoplastic film, in this case polyethylene, was used as the dielectric and the typically low potential strain was amplified more than 40 times by the helical set-up. In a hot press, the thermoplastic film was joined together with layers of carbon black employed as electrodes and a highly elastic thermoplastic polyurethane film. Once the stack was laser cut into thin strips, they were then stretched over the polyethylene (PE) film’s limit of elasticity and released, thus forming a helix. The manufactured prototype showed a maximum strain of 2% while lifting six times its own weight at actuation frequencies of 3 Hz, which is equivalent to a strain rate of 12%/s. This shows the great potential of the newly developed actuator type. Nevertheless, materials, geometry as well as the manufacturing process are still subject to optimization.