Micromachining of NiTi SMA Composite Bimorph for Smart Actuators Using a CO2 Laser

Composites developed by depositing NiTi thin films onto a flexible substrate like Kapton polyimide can be utilized in micro-electro-mechanical systems (MEMS) such as actuators. However, fabricating customized actuators using thin film bimorph is still a challenge. Laser energy has been employed for micromachining of bulk materials and thin metal and plastic sheets for static structures. Continuing on the similar lines, this work attempts to develop smart actuators using micromachining of flexible composite of NiTi/Kapton polyimide bimorph. NiTi shape memory alloy (SMA) bimorph was fabricated using e-beam evaporation technique followed by micromachining using a 10.60 μm CO2 laser. The thickness of the deposited layer was 513 nm. The micromachining was attempted at varying fluences and sample feed. The micromachined edge was created at a laser fluence of 5.1 J/cm2 at sample feed rate of 40 mm/min without any heat-affected zone. The film near the micromachined edge was smooth, however, carbonization of polyimide was observed. Delamination of the deposited NiTi film was not observed after the interaction of laser with the bimorph. However, the laser interaction with the film increases the surface roughness near the micromachined edge compared to that of middle of the actuator.