Soft robots with dynamic motion could be used in a variety of applications involving the handling of fragile materials. Rotational motors are often used as actuators to provide functions for robots (e.g., vibration, locomotion, and suction). To broaden the applications of soft robots, it will be necessary to develop a rotational motor that does not prevent robots from undergoing deformation. In this study, we developed a deformable motor based on dielectric elastomer actuators (DEAs) that is lightweight, consumes little energy, and does not generate a magnetic field. We tested the new motor in two experiments. First, we showed that internal stress changes in the DEAs were transmitted to the mechanism that rotates the motor. Second, we demonstrated that the deformable motor rotated even when it was deformed by an external force. In particular, the rotational performance did not decrease when an external force was applied to deform the motor into an elliptical shape. Our motor opens the door to applications of rotational motion to soft robots.

Rolling motions have been observed in many animals and insects. In the previous fluidic rolling system, a deformed chamber and long cables were imperative to drive the soft rolling actuators, which required high pressure and a sophisticated controlling strategy. In this study, we propose a soft fluidic roller using a simple structure composed of a bendable and twistable electrohydrodynamic (EHD) pump and a layer of natural latex. To realize the rolling motion, we first optimized the electrode and channel height of the EHD pumps using different patterns and designs. We also examined the output power, efficiency, pressure loss, bending, and twisting performance. Subsequently, the optimized electrodes and channel height were selected to design the power source of the EHD roller. This roller was lightweight (0.7 g) with an amount of liquid (0.6 g). This EHD robot can roll as the EHD fluid oscillates under a duty-controlled voltage realized using a high-voltage circuit. Next, we investigated the influence of frictional forces on rolling performance. Finally, the rolling motion in the liquid was demonstrated. This study extends the EHD pumps to independent soft actuators integrated with a soft power source.

An untethered system can realize wide-area activities of soft robots. Herein we develop an untethered DEA wheel (UD-wheel) with a dielectric elastomer actuator (DEA). DEA is a soft actuator driven by electrostatic force. This UD-wheel is a new rotating device that integrates an untethered system and stacked DEAs. The untethered system consists of a small battery and a small high-voltage circuit. All the components are assembled seamlessly. Because the circuit can control four DEAs, the active time that the circuit continues to control the DEAs with a small battery is estimated. The estimated time matches the experimental result. We evaluated the output torque and back-drivability achieved by stacked DEAs installed in a UD-wheel. We also built a theoretical model for an in-depth evaluation. The stacking DEAs method provides a better back-drivability than the reducer method. This study suggests that our untethered rotational system may provide novel functions in soft robotics.

Dielectric elastomer actuators (DEAs) are a promising technology for soft robotics. The use of DEAs has many advantages, including light weight, resilience, and fast response for its applications, such as grippers, artificial muscles, and heel strike generators. Grippers are commonly used as grasping devices. In this study, we focus on DEA applications and propose a technology to expand the applicability of a soft gripper. The advantages of gripper-based DEAs include light weight, fast response, and low cost. We fabricated soft grippers using multiple DEA layers. The grippers successfully held or gripped an object, and we investigated the response time of the grippers and their angle characteristics. We studied the relationship between the number of DEA layers and the performance of our grippers. Our experimental results show that the multi-layered DEAs have the potential to be strong grippers.

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