Electrodeposited magnetostrictive Fe-Ga alloys for miniaturised actuators

The application of magnetostrictive materials in MEMS devices requires the development of suitable micromachining technologies for the deposition and patterning at the microscale. Some alloys of iron and gallium, generally classified under the generic name of Galfenol (Fe_1-x-Ga_x, 0.10 ≤x≤ 0.35), are known for their excellent magnetostrictive and mechanical properties, which make them ideal candidates for the manufacturing of magnetostrictive microactuator devices. Although techniques have been reported for the machining of such materials at a bigger scale, adequate miniaturisation technologies are sought after to enable the integration of Galfenol into MEMS devices. For this purpose, electrodeposition is an appealing technique as it enables rapid and relatively inexpensive growth, while eliminating the need for selective etching processes. This paper presents advances towards the development of a reliable and reproducible process for the electrodeposition of micrometre-thick Galfenol films through systematic experimental characterisation. A preliminary application is finally presented in the form of bilayer cantilevers fabricated by depositing Galfenol on top of copper beams that can be deflected by applying a uniform external magnetic field.