GRIPPERS FOR THE MICRO ASSEMBLY CONTAINING SHAPE-MEMORY ACTUATORS ANDSENSORS

Shape memory alloys (SMA) show a high ratio of work capacity per mater ial volume. This makes the application of SMA especially useful in mic ron-sized systems. The development of robotic grippers is one importan t prerequisite for the successful automation of the assembly of micro systems. Therefore the SMA may also play a role, for example, as actua tors in micron-sized grippers. This paper presents the development of micron-sized grippers. Due to a special relation between the electrica l resistance and the shape change of a NiTi-wire the actuator may also be used simultaneously as a sensor. Besides these functional properti es a superelastic SMA may be used for structural purposes, i.e. as sol id-state flexure hinges. The sensoric features of binary and ternary N iTi-based alloys are investigated using different Ti50Ni50-xCux alloys with 0 < x < 25 at-%. Besides the chemical composition the functional properties are affected by the thermo-mechanical treatment (TMT). Dif ferent TMT of Ti50Ni50-xCux alloys and their influence on the function al properties are compared. The effect of the TMT on the amount and th e stability of the shape memory effect has to be taken into account if the optimum alloy and condition for the use in grippers for micro ass embly are investigated. The function and the properties of the develop ped gripping devices are demonstrated by prototypes.