Electroactive Shape-Fixing of Bucky-Gel Actuators

Electromechanically active polymers (EAP) behave as actuators, i.e., temporarily change their shape when subjected to electric stimulus. However, in applications where a steady state of an actuator is required for an extended period of time (e.g., displaying characters of Braille text), EAPs need an active driving signal. Shape memory polymers, on the other hand, can be fixed to a preferred shape using appropriate stimuli such as temperature change and mechanical stress. Combining the electromechanical properties with the shape memory functionality could increase the efficiency and utility of EAP materials. As bucky-gel actuators--a subtype of EAPs--have been reported to possess a quite characteristic viscoelastic response, this paper proposes to implement them as shape-fixable EAPs. We employ four different shape-fixing techniques, out of which two allow programming the bucky-gel actuator in a controlled direction without any external stress or temperature change. These shape-fixing methods utilize composite driving signal consisting of high-frequency section to generate Joule heating within the material while low-frequency rectangular component deforms the bucky-gel laminate. It is concluded that bucky-gel actuators can achieve steady deformation by using solely the electrical input. By using the proposed methods for adding the shape-fixing functionality to an existing EAP device, no constructional changes of the system are required.