Influence of pre-strain on attributes of Ni-rich NiTi/ Kapton polyimide bimorph for flexible mirrors

Abstract

In this work, Shape Memory Alloy (SMA) based flexible mirrors were fabricated using the E-beam evaporation technique with varying pre-strain on the Kapton polyimide substrate during deposition. The mirrors are crucial for scanning and light beam deflection in MEMS applications. The fabricated bimorphs were investigated for actuation characteristics and reflectance as a mirror in the visible light range. The maximum displacement observed was 75 µm for 1% pre-strained bimorph. The study of shape recovery ratio revealed that bimorph without any pre-strain has the highest shape recovery of 1.637. For mirror application, the reflectance of the bimorph is of prime importance, which was determined by the UV-Visible study of fabricated samples. The maximum reflectance observed was 98.3% for both unstrained and 1% pre-strained samples. Energy Dispersive X-ray Spectroscopy (EDS) study displays the compositional variation of the deposited film. © 2022 Elsevier B.V.