Shape Memory Alloy Actuators for Silicon Microgrippers

The fabrication of shape memory alloy NiTi actuators by femtosecond laser ablation is presented. Processing parameters are examined and the effect of the ablation process on the shape memory material properties is assessed by electron microscopy and differential scanning calorimetry. It is shown that an efficient ablation process with negligible effect on the shape memory properties of the actuator material has been established with a cutting time of ~3 min per actuator. Two different actuator geometries are studied and their performances are compared by measurements of actuator stroke, force and resistance characteristics. A preconditioning procedure for stabilization of the resistance is presented, permitting an actuator control based on the intrinsic sensor effect. A wafer-level integration process of the actuators into silicon microgrippers is described.