Ti-Ni-Cu/polyimide composite-film actuator and simulation tool

Polyimide/Ti49Ni33Cu18 composite films were fabricated by the sputtering of an alloy target. The composite films could be used as a simple actuator by cutting an appropriately shaped piece out of an as-sputtered films with scissors and then connecting it to a battery. In order to investigate the design parameters for the composite-film actuators, Ti-Ni-Cu films with various thicknesses (0.8-13 μm) were deposited on two kinds of polyimide films (Kapton EN and H) with various thicknesses (25-175 μm). The force and stroke of the composite-film actuators were found to vary largely with changes in various parameters such as the thickness ratio of Ti-Ni-Cu and polyimide films and the coefficient of thermal expansion of the polyimide films. A simulation tool based on a simple deformation model for a shape memory alloy was developed, and the effects of dimensional parameters (thickness, length, and width) and material parameters (Young's modulus, elastic strain limit, and transformation strain) on the actuation properties (force and stroke) of the composite-film actuators were systematically investigated on the basis of the simulation results. The simulation results revealed that composite-film actuators allow for various combination of force and stroke. Optimized actuators exhibited a long actuation stroke, a high response speed of 3 Hz, and a large force of 0.4 N.