Polymer sensorised microgrippers using SMA actuation

In this paper a polymer sensorised microgripping tool for micromanipulation is presented. The gripper structure is made by moulding of polyurethane in silicon moulds by the technique of shape deposition manufacturing (SDM), in which the force sensing elements and part of the actuator (in this case, microstrain gauges and SMA (shape memory alloy) wire, respectively) are embedded into the microgripper in one process step. The actuation principle for the microgripper is an SMA wire. The advantages of the fabrication process are low cost and manufacture cycle time. This paper details the technique for fabrication of the microgripper to produce prototypes. These prototypes were then tested and characterised in terms of force output, hysteresis and repeatability. A further miniaturised unsensorised microgripper based on the same actuation principle and fabrication process (but less than half the size) was fabricated to demonstrate the possibility of further downscaling.