Micromachining of functional Ni-Mn-Ga single crystals using femtosecond pulsed laser

Abstract

Ni-Mn-Ga-based magnetic shape memory (MSM) alloy microactuators have a high potential in miniaturized devices for which conventional mechanisms or materials are no longer feasible. However, manufacturing single-crystal-based Ni-Mn-Ga micro actuators is challenging due to their high brittleness, which precludes conventional machining methods. The present work introduces and develops a novel manufacturing method – femtosecond pulse width laser (FPWL) ablation micromachining – for the manufacture of a functional actuators from oriented Ni-Mn-Ga single crystals. Notably, using a green laser (wavelength 515 nm) permits micromachining in the martensitic phase due to the low heating effect of the process. Optimized FPWL parameters are here used to machine a functional actuator from a five-layered modulated (10 M) martensite Ni-Mn-Ga single crystal. The actuator develops a fully reversible and repeatable magnetic-field-induced strain of 6.5% without any post-processing.