To advance the field of soft robotics, novel linear actuators that provide high strain, high strain rate, and high specific power are needed. This work deals with a novel, helically self-coiled dielectric elastomer actuator that exhibits such properties. We present the corresponding manufacturing process, the resulting prototypes, and an analytical modeling approach.

The actuator was manufactured by bonding a strip of unidirectional non-crimp carbon fiber fabric to a pre-stretched silicone film. Due to the tension in the silicone, the strip rolls up and forms a helix when released. The unidirectional fabric was used as an electrode with the fibers running perpendicular to the strip. Therefore, the electrode is highly ductile lengthwise, but the cross-section of the strip remains undeformed despite inherent stress due to the pre-strain. A second electrode placed on the outside of the helix results in a contracting actuator when activated. Prototypes showed strains of up to 5.6 % at actuation frequencies of 2 Hz. To aid the design of the prototypes an analytical modeling approach was developed. Theoretical considerations showed that applying a second electrode on the inside of the helix instead of the outside leads to an expanding actuator. Combining these two approaches will further increase the deformation potential.