Boneless soft robotic fingers cannot apply concentrated forces to pinch a delicate object. This letter reports a three-dimensional design of dielectric elastomer fingers with higher flexural stiffness and close to 90 voltage-controllable bending for object gripping and pinching. It makes use of tension arch flexures to elevate a pre-stretched dielectric elastomer actuator (DEA) into a roof shape and thus magnifies the tension-induced moment, 40 times higher than a flat DEA does, to bend a stiff base frame. Such fingers make normally close-grippers to lift a payload 8-9 times their weight. They also make normally open grippers that pinch a highly deformable raw egg yolk.

Soft grippers based on dielectric elastomer actuator (DEA) are usually too flimsy to perform the task of pick and place on a heavier object given their low payload capacity. This work developed a new design of DEA unimorph consists of a flexible frame holding at a DEA on the discrete support by a stiffer spine-like flexure of 380µm thick Polyvinyl chloride (PVC) sheet. It finds an equilibrium of curling up when the DEA's pre-stretch is partially released; it can electrically unfolds upon a voltage application. This dielectric elastomer unimorph of 3 grams produced a maximum voltage induced bending of close to 90 • and a maximum voltage-induced blocked force of up to 168mN. Given their higher stiffness and large actuation, these 3-D shaped and strengthened DEA unimorphs can make stronger grippers for passive grasping and active pinching.

Dielectric elastomer actuators (DEA), which are capable of muscle-like actuation, have potential to drive insect-inspired flapping-wing robotfly. There have yet been successfully used to drive flapping wings due to various limitations. This paper revisits their use and integration in a thoracic mechanism as either indirect or direct muscles. Three forms of DEA, i.e. folded, rolled, and pre-stretched membrane, were evaluated and integrated in different thoracic mechanisms. The pre-strained membrane of dielectric elastomer was found capable of generating a large rotation. On the other hand, the folded and rolled ones with either no or little pre-strain performed modestly in this flapping-wing application. Pre-strain was found to be important to maximize the actuator performance. In addition, this paper reviewed manufacturing processes for multi-layered DEAs and possibility of introducing pre-strained in the multi-layered layup.

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The contributions of the co-authors are as follows:• I formulated the mathematical models, developed the numerical simulation codes and investigated the performance of a non-uniform width rotating discharge valve in the revolving vane (RV) compressor under the supervision