Commercial dielectric elastomers and their modification methods are reviewed. A method is proposed to overcome the complex interdependency of their properties allowing quick comparison and selection of suitable materials for soft actuator applications.

Although heart transplantation is a gold standard for severe heart failure, there is a need for alternative effective therapies. A dielectric‐elastomer aorta is used to augment the physiological role of the aorta in the human circulatory system. To this end, the authors developed a tubular dielectric elastomer actuator (DEA) able to assist the heart by easing the deformation of the aorta in the systole and by increasing its recoil force in the diastole. In vitro experiments using a pulsatile flow‐loop, replicating human physiological flow and pressure conditions, show a reduction of 5.5% (47 mJ per cycle) of the heart energy with this device. Here, the controlled stiffness of the DEA graft, which is usually difficult to exploit for actuators, is perfectly matching the assistance principle. At the same time, the physiological aortic pressure is exploited to offer a prestretch to the DEA which otherwise would require an additional bulky pre‐stretching system to reach high performances.

This letter deals with the control-oriented modeling of a multilayered dielectric elastomer actuator based tube. The actuator is clamped at both sides and performs a radial displacement. The hyperelastic deformation and the viscoelastic performance, together with the electro-mechanical coupling are considered in the model. With the chosen Yeoh’s model for the Helmholtz free energy function, we aim to model the snap-through effect of this tubular actuator at high applied voltage. Simulation results of the nonlinear dynamic model are later compared with experimental ones in order to identify unknown parameters of the dielectric elastomer, especially to fit the snap-through effect and the high frequency performance. With proper identification process, our model has a good accuracy to fit the physical system (more than 90.27% for a ramp input and more than 82.7% for a step input) and is ready for the future controller design.

Electroactive polymers show promising characteristics, such as lightness, compactness, flexibility, and large displacements, making them a candidate for application in cardiac assist devices. This revives the need for quasi-square wave voltage supply switching between 0 and several kilovolts, that must be efficient, to limit the heat dissipation, and compact in order to be implanted. The high- access resistance, associated with compliant electrodes, represents an additional difficulty. Here, a solid-state Marx modulator is adapted to cope with electroactive polymer characteristics, taking advantage of an efficient energy transfer over a sequential multistep charge/discharge process. To ensure compactness, efficiency, as well as the needs of an implanted device, a wireless magnetic field-based communication and power transfer system has been implemented. This work demonstrates the benefit of this design through simulations and experimental validation on a cardiac assist device. At a voltage of 7 kV, an efficiency of up to 88% has been achieved over a complete charge/discharge cycle.

Specific applications, such as dielectric elastomer actuators (DEAs) or electroactive polymers, require to switch voltage levels exceeding the ratings of existing semiconductor devices. In low power application, reversible flyback are widely used to supply DEAs. Lowering the parallel parasitic capacitance of the high voltage switch is important to improve the energy transfer, while it becomes mandatory to increase the output voltage of flyback above 2.5 kV. In this paper, a Pulsed Transformer Gate Driver (PTGD) is used to drive series-connected MOSFET and therefore push the limits from 4.5 kV up to 16 kV. At these high voltage levels, the structure reveals a drastic voltage unbalance related to the transformer interwinding parasitic capacitance. The compensation method proposed to achieve voltage balance only adds few passive components and reduces significantly the additional parallel capacitance of the switch compared to common load side voltage balancing methods. Finally and as proof of concept, a half-bridge bidirectional converter was designed from this switch technology and drove an actual dielectric elastomer actuator at 16 kV.