Fault-tolerant silicone dielectric elastomers

Abstract

Soft silicone films have garnered a great deal of interest for use in dielectric elastomer transducers due to their excellent properties, including high elongation to rupture, low viscoelasticity, and broad application temperature range. However, silicone films generally have higher stiffness and lower dielectric strength than VHB acrylic elastomers, which limits the achievable actuation strain. Devices based on silicone dielectric elastomers always experience high rates of premature dielectric failure when operated at high strains. The premature failure is characterized by the loss of functionality or mechanical rupture of the material when operated below the material's dielectric strength and elongation to rupture. The use is reported of ultrathin coatings of single-walled carbon nanotubes (SWNTs) as the compliant electrodes, which can overcome the issue of premature failure. The self-clearing of the SWNT electrodes in the event of localized dielectric breakdown improves the apparent dielectric strength of the material by isolating the regions of reduced dielectric strength. The actuators may be operated at higher than 50% area strain with reasonably long lifetimes. High strains were measured between −40 and 80°C and in a broad frequency range up to 100 Hz. The fault tolerance introduced by the SWNT electrodes should broaden the application scope of silicone dielectric elastomers.