Influence of Laser Micromachining and Compositional Variation of NiTi on NiTi/Kapton Polyimide Bimorph Actuators for Opto-Mechatronics Applications

Abstract

Structures fabricated 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, the development of customized actuators with different fabrication processes can alter the characteristics of thin film and actuation. Micromachining of the bimorph structure using laser energy results in accurate shape generation and can anneal the deposited film due to the absorption of laser heat into the bimorph. In this work, the NiTi Kapton polyimide bimorph actuator was fabricated out of the bimorph sheet using laser-assisted micromachining. The micromachining was performed by a 1064 nm fiber laser at optimized parameters of 5 W laser power, 5 mm/s laser speed, and 50 μm laser spot diameter. The actuators were customized into shapes of triangles of 10 mm side. The interaction of the laser with the bimorph structure has resulted in the grain refinement of the deposited NiTi film revealed by the SEM analysis. The variation in phase transformation temperature was also studied with differential scanning calorimetry. The electrical actuation results of the actuators displayed an improvement of 54% for the laser micromachined actuator. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.