Dielectric elastomer (DE) single films for bending actuators are normally used with pre-stretch to increase the performance of the actuation. However, pre-stretch requires a high effort in the production of the actuators. In this work, a simple DE bending actuator in a unimorph configuration with high actuation performance is presented. For the manufacturing of the actuator, a silicone film is coated with conductive carbon nanoparticles in a silicone matrix as electrodes on both sides and laminated with a non-stretchable, but highly bendable and light weight polymer film, which acts as a strain limiting layer. Stiffening bars on the strain limiting layer impede an uncontrolled actuator deformation. The bending angle and the displacement of the actuator tip were measured at variable field strength up to 80 kV/mm. In a single DE layer configuration with an electrode area of 50 mm x 30 mm, a bending angle of 15° and a tip displacement of 7 mm were reached. A mathematical model for the bending actuator was applied to compare experimental and theoretical results and to optimize the relevant parameters. By using thermoplastic polyurethane (TPU) as an alternative elastomer material, a bending angle of 40° and a tip displacement of 18 mm could be achieved with the same actuator dimensions and optimized parameters. The simple unimorph bending actuators are promising tools for sensitive grippers on soft robots.

Unimorph bending actuators based on dielectric elastomers (DE) are promising components for soft robotic grippers in analogy to the capabilities of the human hand. In a simple manufacturing process of the unimorph actuator, a bendable, but not stretchable passive carrier film is laminated with an active DE film, which expands in the electric field and generates a large bending deformation of the laminated composite film along its length dimension. The actuation performance in terms of the bending angle, actuator tip displacement and blocking force depends not only on the geometrical design of the unimorph actuator, but also on the properties of the used materials such as the Young’s moduli of the passive film and the elastomer film as well as the elastomer’s permittivity. To evaluate the influence of all relevant geometrical and material parameters on the actuation performance, a simple mathematical model was developed. Additionally, DE unimorph actuators were manufactured with silicone elastomer and their performance was experimentally investigated. The results of calculations are compared with those of the corresponding measurements and exhibit a high degree of quantitative agreement. Furthermore, the dependence of the actuator performance on various geometrical and material parameters (thickness of the dielectric and of the carrier film, permittivity and Young’s modulus of the dielectric) is predicted with the mathematical model. These calculations pave the way to a unimorph actuator with strongly improved performance. The key for this high performance is the simultaneous enhancement of the permittivity and the Young’s modulus of the dielectric. Thermoplastic polyurethane (TPU) fulfills these requirements and unimorph actuators based on TPU actually confirm the predicted high performance experimentally. By this way, the simple mathematical model offers a powerful and efficient tool for the optimization of unimorph actuators.