Programming Complex Shapes in Soft Electrically-Active Materials

Electrically-activated elastomeric materials hold great promise to bring alive the dream of autonomous life-like soft robots. Fast actuation of materials that match the compliance and rheology of biological materials could enable breakthroughs in realistically mimicking the rippling fin motion of a cuttlefish, the dynamic acrobatics and dexterity of the bat wing membrane during flight, and even simulate the contractions and twists of arteries and the left ventricle of the heart. There have been several soft materials proposed to date ranging from very soft hydrogels to shape memory polymers whose shape change can be triggered by heat, magnetic field, electric field, and light. Of the soft active materials investigated to date, dielectric elastomers have garnered significant interest due to their nontrivial and reversible fast deformations in response to an external stimulus. Another soft elastomer demonstrating large deformations are liquid crystal elastomers via light and thermal actuation near their phase transition temperature, and more recently via electric field when configured as a planar capacitor. We discuss programming complex three-dimensional shapes using soft electrically-active elastomeric materials by controlling the anisotropy and mode of electric activation. The programming is achieved by patterning contractile fibers and selective activation. We introduce a computational model for simulating the shape-changing phenomena. The model is based on a new constitutive formulation within a finite viscoelastic framework. Computational implementation using a finite element user-subroutine allows us to simulate the complex shape response. Several examples of the achievable 3D complex shapes are demonstrated.