Intrinsically Anisotropic Dielectric Elastomer Fiber Actuators

Biological muscles are composed of aligned actuatable fiber units to generate directional linear output, inspiring the design of microstructures in artificial muscles. However, synthetic soft elastomers generally possess isotropic mechanical properties; therefore, a promising artificial muscle (dielectric elastomer actuator) generally outputs nondirectional force or deformation. In this work, we report a muscle-mimetic anisotropic dielectric elastomer fiber with directional output driven by electric field. The millimeter-in-diameter fibers are fabricated by rolling elastomeric ultrathin films of triblock copolymer that are pretreated to generate aligned nanostructures and network strands. We theoretically and experimentally reveal that a moderate orthogonal modulus ratio of radial to axial directions (2.8) leads to highly directional actuation, enhancing linear axial strain by 100%. Assembling the anisotropic fine fibers into bundles is able to scale up force output and enables variable motion modes such as extension, bend, and rotation.