Investigation of laser-assisted micromachining of NiTi SMA bimorph based actuators toward developing optical shutters

Abstract

This work explores laser-assisted micromachining for the precision cutting of NiTi SMA-based bimorph in a single-pass laser scan. NiTi SMA bimorph was fabricated using the e-beam evaporation technique followed by micromachining using a 1064 nm fiber laser. The influence of laser power, laser speed, spot diameter, and laser travel direction on kerf width and heat-affected zone after micromachining was studied using the design of experiments. The optimized parameter for micromachining was at laser power 5 W with 5 mm/s laser speed and 50 μm spot diameter. Various shapes were cut at the optimized parameter, including an optical shutter of a diameter of 30 mm. A laser speed of 6 mm/s has produced microchannels in the bimorph due to NiTi film removal only. The SEM analysis of the shutter reveals the formation of refined grains at micromachined edges compared to the center of the actuator. Fabricated optical shutter shows negligible optical transmittance in the 450 to 700 nm wavelength range.