Numerical investigations on dielectric stack actuators with perforated electrodes

Dielectric elastomer (DE) actuators could have great potential for innovative solutions in different applications due to their large deformation capabilities, low cost and lightweight nature. One of the main technical challenges in the development of DE actuators is to realize highly conductive, compliant electrodes that do not constrain the large strain of the elastomer material. Metal electrodes are normally not feasible due to their high stiffness, though their electrical properties are excellent. Therefore mostly powder or grease electrodes have been realized so far, yielding good results in the laboratory. However, for many applications in industrial use, stack actuators with compliant electrodes have some disadvantages regarding processing and durability. Additionally the inhomogeneous strain distribution along the stack due to boundary constraints leads to performance losses, especially for thin actuators. Therefore a new design approach with rigid, perforated metal electrodes is chosen. This stack actuator only contracts in one direction whereas all the other directions remain undeformed. To find an optimal electrode design, a numerical model is set up for a small cut-out element of the actuator and different physical effects are subsequently taken into account to match reality as closely as possible. Finally, a functional demonstrator is built and characterized experimentally. The studies show the great potential for elastomer actuators with perforated, rigid electrodes and also demonstrate the need for a careful design and the advantage of numerical optimization methods.