Electromechanical Actuator with Controllable Motion, Fast Response Rate, and High-Frequency Resonance Based on Graphene and Polydiacetylene

Although widely investigated, novel electromechanical actuators with high overall actuation performance are still in urgent need for various practical and scientific applications, such as robots, prosthetic devices, sensor switches, and sonar projectors. In this work, combining the properties of unique environmental perturbations-actuated deformational isomerization of polydiacetylene (PDA) and the outstanding intrinsic features of graphene together for the first time, we design and fabricate an electromechanical bimorph actuator composed of a layer of PDA crystal and a layer of flexible graphene paper through a simple yet versatile solution approach. Under low applied direct current (dc), the graphene–PDA bimorph actuator with strong mechanical strength can generate large actuation motion (curvature is about 0.37 cm<sup>–1</sup> under a current density of 0.74 A/mm<sup>2</sup>) and produce high actuation stress (more than 160 MPa/g under an applied dc of only 0.29 A/mm<sup>2</sup>). When applying alternating current (ac), this actuator can display reversible swing behavior with long cycle life under high frequencies even up to 200 Hz; significantly, while the frequency and the value of applied ac and the state of the actuators reach an appropriate value, the graphene–PDA actuator can produce a strong resonance and the swing amplitude will jump to a peak value. Moreover, this stable graphene–PDA actuator also demonstrates rapidly and partially reversible electrochromatic phenomenon when applying an ac. Two mechanismsthe dominant one, electric-induced deformation, and a secondary one, thermal-induced expansion of PDAare proposed to contribute to these interesting actuation performances of the graphene–PDA actuators. On the basis of these results, a mini-robot with controllable direction of motion based on the graphene–PDA actuator is designed to illustrate the great potential of our discoveries for practical use. Combining the unique actuation mechanism and many outstanding properties of graphene and PDA, this novel kind of graphene–PDA actuator exhibits compelling advantages to traditional electromechanical actuation technology and may provide a new avenue for actuation applications.