Magnetostrictive thin film actuation

Magnetostrictive thin film (MTF) actuators, that take advantage of high energy density and remote excitation capability of magnetostrictive material is proposed as a new actuation method for micro-electro-mechanical systems (MEMS). The material composition of MTF actuator and its configuration can be optimized for different applications. With micro fabrication techniques it is feasible to scale down to micron meter level and integrate with control and driving components to develop MTF-based MEMS devices.; The fabrication of MTF devices was investigated using two methods, viz., dry and wet etching to thin and pattern the substrate. The magnetostrictive thin film layer was deposited with either electron beam or DC magnetron sputtering. The preliminary results showed hat the DC magnetron sputtering is a better method. Based on the experimental results of trial runs a detailed fabrication protocol of MTF was developed.; To study the performance of MTF actuators, an analytical model of MTF cantilever structure is presented. Finite element models which can analyze the MTF actuator in a more complex situation and take account the effect of its driving magnetic circuit were developed. The static experimental results demonstrated that the cantilever MTF actuators that are DC magnetron sputtered with Sm-Fe-B exhibit magnetostriction of up to 160 ppm at magnetic fields as low as 1000 Gauss.; Eigenvalue frequency finite element analysis was conducted to investigate dynamic performance. Preliminary experimental results of dynamic tests showed the importance of high frequency magnetic driving circuit which must be customer designed and optimized at the system level. Three magnetic circuits, viz., resonant, trans former/autotransformer, and hybrid methods were investigated. Only the hybrid magnetic circuit increased the magnetic field with the magnetostrictive core. Dynamic experimental results shows that the deflection MTF deflected by up to about 6 mum at the resonant frequency of 1000 Hz and decrease at higher frequencies. The frequency response of MTF actuators for this research work is limited by the size of the samples and the decrease of magnetic field at high frequencies. The frequency response could however be increased by reducing the size of MTF to MEMS devices level and access to a high frequency magnetic field generator.; Two most suitable applications of MTF are proposed along with several other potential applications. Compared to bulk magnetostrictive materials, MTF are particularly suitable for low force, high frequency (>10 KHz) and high reliability MEMS applications where high voltage power supply cannot be used or remote excitation is desirable.