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.

The Current State of Silicone-Based Dielectric Elastomer Transducers

“…Lifetime is a key aspect in the further improvement of DETs, and it is vital for the potential commercialisation of the technology. A potential way to obtain higher lifetimes is by introducing self‐healing capabilities into both elastomers and electrodes, as seen recently. It will be interesting to follow the developments of self‐healing materials for DETs and how this will affect materials research and especially future DET products.…”

Electrical and Mechanical Self‐Healing in High‐Performance Dielectric Elastomer Actuator Materials

“…An improvement in breakdown strength of 18% was achieved compared to non-cleared material, and the loss of active area and capacitance during the pre-clearing process was less than 5%. Carbon based electrodes for dielectric actuators have also been developed that exhibit self-clearing for dielectric elastomer applications, which includes the use of graphite nano-platelets in a silicone matrix or carbon nanotubes [7] [8] [9] [10] [11] .…”

Self-Healing and Damage Resilience for Soft Robotics: A Review

“…This degradation breaks the local continuity, and therefore conductivity, of the electrode, preventing further loss of energy through the damaged area, though also locally increasing the stiffness of the electrode. Initial results demonstrated self-clearing damage resilient electrodes fabricated by spray-coating onto dielectrics made of acrylic elastomers, and further work demonstrated self-clearing CNT electrodes on silicone dielectric layers as well (Yuan et al, 2010). Silicone as the dielectric material enables tunability of the speed of the self-clearing response by changing the thickness of the dielectric layer.…”