Multifunctional shape memory electrodes for dielectric elastomer actuators enabling high holding force and low-voltage multisegment addressing

We present a novel configuration of a dielectric elastomer actuator (DEA) using electrodes made of a shape-memory polymer. DEAs are an efficient class of flexible electromechanical transducer. They have been incorporated into a variety of elegant devices, such as microfluidic devices, tunable optics, haptic displays, and minimum-energy grippers, to name a few. Dielectric elastomer minimum energy structures (DEMES) take advantage of the prestretch of the dielectric elastomer actuator to bend a non-stretchable but flexible component to perform mechanical work. DEMES grippers are capable of grasping objects, but with only small to moderate forces. We report on the use of a conductive shape memory polymer (SMP) as the electrode for a DEA gripper. The SMP electrodes allow the DEA to be rigid in the cold state, offering far greater holding force than a conventional DEA. Joule heating applied to the shape memory electrodes soften them, allowing for electrostatic actuation. Cooling then locks in the actuated position without the need for continued power to be supplied. Additionally, the Joule heating voltage is at least one order of magnitude less than electrostatic actuation voltages, allowing for addressing of multiple actuator elements using commercially-available transistors. The shape memory gripper incorporates this addressing into its design, enabling the three segments of each finger to be controlled independently.