Dielectric elastomer actuators (DEAs) have attracted growing research interest over the past two decades for their large actuation strain, inherent compliance, and low cost. The conical DEA configuration is particularly attractive thanks to their simple structure and high force/stroke actuation. A double cone DEA design with two antagonistic membranes allows active bidirectional actuation. However, in existing double cone DEA designs, the two membranes are rigidly coupled, which restricts their relative actuation response under periodic electrical input to 180° out-of-phase operation. This work presents a magnetically coupled DEA with compliant coupling by a magnetic repulsion. The compliant coupling allows two separate inputs with a fully adjustable phase difference. The current prototype demonstrates a peak normalized stroke of 14% (relative to the nominal DEA height) at a phase shift of 180° and a normalized linear expansion between the two membranes of up to 8.3% (relative to the nominal DEA height) at a phase shift of 0° at 0.5 Hz. This results in several emerging actuation behaviors, which could potentially be suitable for controllable shape changing actuations, active vibration damping, and bioinspired locomotion.

The emerging demand for bio-inspired soft robotics requires novel soft actuators whose performance exceeds conventional rigid ones. Dielectric elastomer actuators (DEAs) are a promising soft actuation technology with large actuation strain and fast response. Cone DEAs are one of the most widely adopted DEA configurations for their compact structure and large force/stroke output with several configuration variations developed in recent years. By driving at a resonant frequency, the cone DEAs show a significant amplification in their power outputs, which demonstrates their suitability for highly dynamic robotic applications. However, it is still unclear how the payload conditions could affect the power outputs of cone DEAs and no work has compared the output performance of different variations of cone configurations. In this work, by considering conical configuration DEAs with generalized dissipative payloads, we conduct an extensive study on the effects of payload conditions on the power outputs of the cone DEA family. Additionally, we benchmark the performance of different cone DEA configurations and illustrate the fundamental principles behind these output patterns. The findings reported in this work establish guidelines for designing high-performance cone DEA actuators.

Leveraging the instability in bistable structures to rapidly release the stored energy is often observed in nature to improve survival and reproduction. Bistable actuators have endowed soft grippers with superior performances such as fast response and self-lock ability. However, current bistable grippers are merely determined by their structural parameters in the design processes, and their grasping modes are usually restricted. In this article, we propose a novel type of reprogrammable bistable actuators. We introduce the design, modeling, and verification of the actuators. The results show that when reprogrammed to its ultrasensitive state with a minimal energy barrier, the trigger force required to induce the fast snap-through can be reduced to less than 0.005 times of its maximum value. In this process, only a minimal energy of 0.001 mJ was needed to trigger the fast energy release of 13.1 mJ. To demonstrate the advances and uniqueness of the proposed actuator, we also prototyped multiple grippers for multimodal, fast, and ultrasensitive grasping. In the ultrasensitive state, the gripper was able to respond to the contact of the swimming fish and capture it in 0.18 s. This work broadens the frontiers of bistable actuators in the design of functional robotic grippers.

Over the last decade, many bio-inspired crawling robots have been proposed by adopting the principle of two-anchor crawling or anisotropic friction-based vibrational crawling. However, these robots are complicated in structure and vulnerable to contamination, which seriously limits their practical application. Therefore, a novel vibro-impact crawling robot driven by a dielectric elastomer actuator (DEA) is proposed in this paper, which attempts to address the limitations of the existing crawling robots. The novelty of the proposed vibro-impact robot lies in the elimination of anchoring mechanisms or tilted bristles in conventional crawling robots, hence reducing the complexity of manufacturing and improving adaptability. A comprehensive experimental approach was adopted to characterize the performance of the robot. First, the dynamic response of the DEA-impact constraint system was characterized in experiments. Second, the performance of the robot was extensively studied and the fundamental mechanisms of the vibro-impact crawling locomotion were analyzed. In addition, effects of several key parameters on the robot’s velocity were investigated. It is demonstrated that our robot can realize bidirectional motion (both forward and backward) by simple tuning of the key control parameters. The robot demonstrates a maximum forward velocity of 21.4 mm/s (equivalent to 0.71 body-length/s), a backward velocity of 16.9 mm/s, and a load carrying capacity of 9.5 g (equivalent to its own weight). The outcomes of this paper can offer guidelines for high-performance crawling robot designs, and have potential applications in industrial pipeline inspections, capsule endoscopes, and disaster rescues.

In nature, animals reduce their cost of transport by utilising elastic energy recovery. Emerging soft robotic technologies such as dielectric elastomer actuators (DEAs) offer an advantage in achieving biomimetic energy efficient locomotion thanks to their high actuation strain and inherent elasticity. In this work, we conduct a comprehensive study on the feasibility of using antagonistic DEA artificial muscles for bio-inspired robotics. We adopt a double cone DEA configuration and develop a mathematical model to characterise its dynamic electromechanical response. It is demonstrated that this DEA design can be optimised in terms of the maximum work output by adjusting the strut height design parameter. Using this optimised design, we analyse the power/stroke output and the electromechanical efficiency of the DEA and show how these actuation characteristics can be maximised for different payload conditions, excitation frequencies and actuation waveforms. The elastic energy recovery from the DEA is then demonstrated by reducing the duty ratio of the actuation signal and thus allowing the stored elastic energy in the DEA membranes to contribute to the work output. A bio-inspired three-segment leg prototype driven by the same actuator is presented to demonstrate that the same energy recovery principle is feasible for bio-inspired robotics.

Dielectric elastomer actuators (DEAs) are an emerging soft actuation technology that have advantages in large actuation strain, inherent compliance and low cost. Resonant actuation of DEAs has been shown to increase the actuation stroke and power output and has been utilized in applications such as robotic locomotion and loudspeakers. In this work, we present a planar circular dielectric elastomer oscillator (DEO) that can exert out-of-plane deformation as large as 80% of its own diameter at resonance. By experiments and model simulation we show that this simple DEO design exhibits complex nonlinear responses, including multiple solutions, sub- and super-harmonics, and exhibits multiple resonant peaks. The DEO performance is characterized against membrane pre-stretch and the weight of the attached mass and its actuation signals (DC and AC amplitudes). The resonant frequency and the amplitude are found to be easily tuned by varying these parameters. Such large stroke output and highly tunable resonance make this DEO a promising candidate for applications such as active vibration absorption, embedded loudspeakers, soft pumps and robotic locomotion.