Self-clearable carbon nanotube electrodes for improved performance of dielectric elastomer actuators

Abstract

Dielectric elastomer actuators which consist of an electrode/dielectric elastomer/electrode sandwich structure show greater than 100% electromechanical strain performance when high electrical field is applied. The strain in the dielectric elastomer film occurs due to attraction of opposite charges across the dielectric film and repulsion of similar charges on each compliant electrode. Structural defects present in these elastomers such as gel particles, uneven thickness, and stress concentration may cause dielectric breakdown, leading to premature failure during continuous or repeated actuations. Dielectric breakdown consequently reduces production yield and device lifetime. Carbon nanotubes (CNTs) have been introduced as compliant electrodes for dielectric elastomers. Higher than 100% electromechanical strain was obtained with ultrathin CNT electrodes due to the high aspect ratio and the high electrical conductivity of the nanotubes. These ultrathin CNT electrodes also exhibit fault-tolerance in dielectric elastomers through the local degradation of CNTs during dielectric breakdown. The degraded areas electrically isolate the defects, while keeping the rest of the elastomer active. The self-clearing electrodes significantly increase the lifetime of the dielectric elastomers, making the dielectric elasomer actuator much more reliable.