Dielectric elastomer-based crawling robots can utilize a voltage-induced deformation to achieve prescribed crawling movements. Although a rich repertoire of robots have been proposed with various design schemes, developing the logic and a unified methodology is hard. This work designs inchworm-inspired crawling robots based on computational optimization. An improved shape and topology optimization method is developed using a fat B-spline curve to generate a stable frame for the dielectric elastomer actuators (DEAs). An optimization framework is proposed, and the updating algorithm is assessed with a sensitivity analysis. The leg-DEA and abdomen-DEA of the crawling robot are modeled and designed automatically with iterations implemented in finite element simulation. An optimization soft crawling robot was fabricated and tested, which can move smoothly along the ground.

A soft bistable actuator can generate high-speed motion between two prescribed stable positions, which is very useful for boosting the actuation of soft robots. Generally, the stroke of such an actuator is completely determined once the design is finalized, which prohibits its applications in robots that perform multiple tasks. In the current work, a bistable actuator with adjustable characteristics is proposed by exploring its strain energy landscape, in which the energy barrier is manipulatable via electroactive twisted and coiled polymer fibers. As such, the actuator can operate in either bistable or postbistable mode, both of which exhibit adjustable stiffness. A kinetostatic model that combines the chained beam constraint model and the mechanics of electroactive materials is established to characterize the actuator design. Experimental results validate the kinetostatic model and the behaviors of the actuator. As a robotic demonstration, a gripper that is formed by two actuators is prototyped, and it exhibits an adjustable load capacity (up to 6.5 times its weight under a 3 V voltage).

Dielectric elastomers (DE) are ideal electro-active polymers with large voltage-induced deformation for the design and realization of soft machines. Among the diversity of configurations of DE-based soft machines, dielectric elastomer minimum energy structures (DEMES) are unique due to their ease of fabrication, readiness to extend into multiple segments, and versatility of design configurations. Despite many successful demonstrations of DEMES actuators, these DEMES devices are limited to immobile use. We report several possible implementations of soft mobile machines through the combination of DEMES design, finite element simulation, and experiment. Our designs mimic the biomimetic locomotion of inchworms and marry complex components such as ratchet wheels with soft DEMES actuators. We even elucidate that buckling of DE can be harnessed to achieve asymmetric feet, which is otherwise realized via more complicated means. The examples presented here enrich DE devices’ design and provide valuable insights into the design and fabrication of soft machines that other soft-active materials enable. All the codes and files used in this paper can be downloaded from GitHub.

The dielectric elastomer (DE) is a new kind of functional polymer that can be used as a smart actuator due to the large deformation induced by voltage excitation. Dielectric elastomer actuators (DEAs) are usually excited by dynamic voltages to generate alternating motions. DEAs are prone to premature breakdown failure during the dynamic excitation, while the research on the breakdown of DEAs under cyclic voltage excitation is still not fully revealed. In this paper, the dynamic breakdown behaviors of DEAs made from VHB4910 film were experimentally investigated. The factors affecting the breakdown behavior of DEAs under dynamic voltages were determined, and the relevant changing laws were summarized accordingly. The experimental results show that under dynamic voltage excitation, the critical breakdown voltage of DEAs were augmented slowly with voltage frequency and showed a substantial dispersion. In addition, the maximum cycle numbers before breakdown were significantly affected by voltage parameters (such as frequency, amplitude, waveform). Finally, the underlying mechanisms of breakdown under cyclic voltages were discussed qualitatively, a power-law equation was proposed to characterize the maximum cycle number for the dynamic breakdown of DEAs, and related parameters were fitted. This study provides a new path to predict the service life of DEAs under dynamic voltage.