The actuation performance of dielectric elastomers (DE) is determined by the electric field when voltages are applied. As the field-dependence is quadratic, higher voltage leads to more efficient actuation. The limiting factor, however, is dielectric breakdown. Due to early-stage and complex manufacturing processes, thin films at present may still contain local imperfections, limiting the overall breakdown field and sometimes causing early breakdown in DE actuators. In particular, when manufacturing multi-layer actuators, a premature breakdown in only one layer causes failure of the entire actuator system. To overcome this problem and to increase the yield of functional actuators, this paper presents a novel method to test and repair DE layers. In a first step, a DE layer is tested for required breakdown voltage in a specially designed breakdown tester and the location of early breakdown spots is identified. In a second step, a method for the repair of these breakdown spots is introduced. A final validation of the repaired DE layer for quality control concludes the process, hence ensuring higher yield of functional actuators in an early manufacturing stage. The testing process using a specially designed breakdown box is described as well as the subsequent repair method of a patch/glue combination. Results about the influence of the repaired spots on the stress/strain behavior of a silicone thin film w/o electrode as well as the performance of the DE prepared with screen-printed carbon black electrodes are included in the presentation.
Dielectric Elastomer Actuators (DEAs) are known for their outstanding properties such as low weight, high energy density and self-sensing capability. Compared to conventional magnetic actuators, they are manufactured from generally inexpensive and widely available polymer materials, making the technology particularly attractive for developing actuator systems that are potentially low-cost and serve a wide range of applications. This advantage can be further enhanced by developing scalable and standardized system designs that use identical parts in order to reduce product variation and enable high volumes in a mass production process. Following this approach, this paper introduces a low-profile and compact linear actuator design, which provides a configurable force and stroke transmission in order to serve different load-profiles without changing shape and dimension of the DEA itself. The design is based on rectangular-shaped, in-plane operating DEAs coupled to a unibody linkage mechanism, which is likewise flat and based on compliant joints and rigid links. A negative rate stiffness mechanism enables to increase the performance output of the actuator system in terms of cyclic converted energy in quasi-static operation. By configuring the lever ratios of the input and output sides accordingly, it can either behave stroke-magnifying or force-magnifying. Thus, as an example, a system with negative and one with positive transmission ratio are realized and characterized with respect to their force and their stroke behavior.
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