Intrinsically Anisotropic Dielectric Elastomer Fiber Actuators

Abstract

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.

Hybrid artificial muscle: enhanced actuation and load-bearing performance via an origami metamaterial endoskeleton

“…5f), where M is the mass of the DEA and KDOM, m is the mass of the weight, g is the gravitational acceleration, and δ is the free displacement. 54…”

An Anisotropic Dielectric Elastomer Actuator with an Oriented Electrospun Nanofiber Composite Film

“…[24][25][26][27] Although the stiff fiber fillers can be adhered to the surface of DEs as a function of its inherent tackiness, such a two-layer strucure would induce interfacial shear stress because of modulus mismatch and lead to electromechanical failure. [12,28] Alternatively, roller configuration of DEs can also be used to convert area expansion into the linear deformation ≈9.8% along the axis at…”

“…[ 24–27 ] Although the stiff fiber fillers can be adhered to the surface of DEs as a function of its inherent tackiness, such a two‐layer strucure would induce interfacial shear stress because of modulus mismatch and lead to electromechanical failure. [ 12,28 ] Alternatively, roller configuration of DEs can also be used to convert area expansion into the linear deformation ≈9.8% along the axis at 37.5 V µm −1 . [ 29 ] Recently, researchers have proposed the pre‐stretch and thermal relaxation treatment for the poly (styrene‐ b ‐butyl acry‐late‐ b ‐styrene) (SBAS) to obtain anisotropic DEs with the length strain of 6% at 37 V µm −1 .…”

Influence of the active-to-passive area ratio on the electrically induced strain of a fiber-reinforced dielectric elastomer actuator

“…However, many applications such as soft robotic grippers or biologically inspired robots, require actuators with highly anisotropic deformation characteristics. Current approaches to achieve anisotropic properties in actuators are 3D-printed patterns coupled to the DEA structure 1 , wrinkled DE films and electrodes 2 or rolled DEAs into cylindrical-shaped actuators 3 . A promising approach to obtain DEA structures with a high degree of anisotropy is to incorporate stiff fibers into DE layers 4 or actuator electrodes 5 (Fig.…”