Axial force transmission in flexible bowtie dielectric elastomer actuators

Abstract

A long strip of a pre-stretched dielectric elastomer actuator (DEA) is necessary for strain accumulation, but it relaxes laterally and thickens non-uniformly. As compared to a short strip under the same voltage activation, the long relaxed strip is subjected to a less electric field and, thus, undergoes less active strain. Here, we developed a flexible ladder frame to reinforce and divide the long DEA in a bowtie series. When being pulled, the ladder frame unbuckled; it, in turn, helped to pre-stretch tautly the DEA membrane. Interestingly, its flanges enhance force transmissions, acting like tensioning cables for a suspension bridge. Hence, the maximum isometric stress of this bowtie series was 24% higher than the short pure-shear one and 6.5 times the long uniaxial one. With 2.2 times enhanced dielectric strength across a taut DEA membrane, the bowtie series generated an isotonic strain 3.2 times that a long non-reinforced and relaxed DEA did. Hence, the reinforced DEAs can provide a more forceful drive for bio-inspired robots.