High-cycle electromechanical aging of dielectric elastomer actuators with carbon-based electrodes

Abstract

We present high-cycle aging tests of dielectric elastomer actuators (DEAs) based on silicone elastomers, reporting on the time-evolution of actuation strain and of electrode resistance over millions of cycles. We compare several types of carbon-based electrodes, and for the first time show how the choice of electrode has a dramatic influence on DEA aging. An expanding circle DEA configuration is used, consisting of a commercial silicone membrane with the following electrodes: commercial carbon grease applied manually, solvent-diluted carbon grease applied by stamping (pad printing), loose carbon black powder applied manually, carbon black powder suspension applied by inkjet-printing, and conductive silicone-carbon composite applied by stamping. The silicone-based DEAs with manually applied carbon grease electrodes show the shortest lifetime of less than 10 5 cycles at 5% strain, while the inkjet-printed carbon powder and the stamped silicone-carbon composite make for the most reliable devices, with lifetimes greater than 10 7 cycles at 5% strain. These results are valid for the specific dielectric and electrode configurations that were tested: using other dielectrics or electrode formulations would lead to different lifetimes and failure modes. We find that aging (as seen in the change in resistance and in actuation strain versus cycle number) is independent of the actuation frequency from 10 Hz to 200 Hz, and depends on the total accumulated time the DEA spends in an actuated state.

An ultra-fast mechanically active cell culture substrate

“…Carbon-grease or carbon-powder electrodes are not suitable materials since they would not withstand most sterilization protocols and contaminate the culture medium. Structurally stable electrodes 47 such as carbon-elastomer composite 48 or implanted gold electrodes 49 are required for cell stretching applications. We selected a carbon-elastomer composite 50 that was pad-printed and cured on the silicone membrane to create robust and cytocompatible electrodes with minimal stiffening impact.…”

A Review of Dielectric Elastomer Generator Systems

“…[83] In addition to dielectric and electrode properties, a relevant performance index for DEGSs is the number of electromechanical cycles that they can withstand. Lifetime of DE transducers has been mostly studied with reference to actuators, [84][85][86] with a few works specifically referring to DEGs. [49,67] Silicone-based DE actuators have been reported to achieve maximum lifetimes over 10 8 cycles.…”

Latchable microfluidic valve arrays based on shape memory polymer actuators

“…The flow rate at the open state decreases by 30% over the thousands of cycles. This is mainly related to a slow degradation (resistance increase) of the carbon-based electrodes, as reported by de Saint-Aubin et al 32 For simplicity of the setup, a constant voltage scheme was used for Joule heating rather than a constant power circuit. As the resistance of the heater increases with the number of deformation cycles, the heater power at fixed voltage decreases, leading to less heating, and hence less softening of the SMP membrane, which thus no longer fully opens, leading to a reduced liquid flow rate.…”