Electrostatic Bellow Muscle (EBM): flexible multipurpose electrostatic actuator and energy harvester based on fluid dielectric

Actuators driven by electrostatic force represent a very promising opportunity for the development of advanced robotic systems. Dielectric elastomer actuators have been long investigated and more recently devices based on fluid dielectric have been proposed as a possible alternative that shows remarkable performance. Here, we present a novel electrostatic actuator that is made of thin polyimide films and liquid dielectric, combined with rigid plates assembled to form a circular actuation unit that undergoes to out-of-plane expansion/contraction. Prototypes of these actuation units have been tested showing a contraction of up to 40%, a maximum power density during contraction of 100 W/kg, a maximum strain rate of 1000% per second, a bandwidth of approximately 10 Hz, and the ability to lift hundreds of times their weight. Additionally, these units resulted easy to manufacture in different dimensions and can be assembled in arrays and stacks to form an electrostatic bellow muscles (EBM) that can be effectively employed as a contractile artificial muscle, as pump and as electrostatic generator. EBM demonstrated their flexibility in matching a wide range of requirements and scales in terms force-displacement combinations and bandwidth. The compact 2-D shape, the low-cost of components, the simple assembling procedure, the high level of reliability and the relevant performance make the EBM a possible enabling technology for a variety of high-performance robotic and mechatronic systems.