Ji-An Chen

Giant magnetoimpedance and stress-impedance effects in multilayered FeSiB/Cu/FeSiB films with a meander structure

Giant magnetoimpedance (GMI) and giant stress-impedence (GSI) effects were realized in multilayered FeSiB/Cu/FeSiB films with a meander structure by magnetron sputtering on thin glass substrates. The GMI and GSI effects were studied in the frequency range of 1-40 MHz for the multilayered FeSiB/Cu/FeSiB films. Experimental results show that a large negative GMI ratio of -23% is obtained at H a = 12 kA/m for a frequency of 20 MHz. The GSI ratio is -20% for a frequency of 1 MHz with the deflection of 150 μm of the multilayered FeSiB/Cu/FeSiB films. The GSI effect is attractive for stress or pressure sensor applications.

Fabrication of ultralow-profile micromachined inductor with magnetic core material

We have fabricated a microinductor with an ultralow profile by a microelectromechanical systems (MEMS) technique. The fabrication process uses UV-LIGA, dry etching, fine polishing, and electroplating to achieve high performance. The dimensions of the inductor are 1500 /spl mu/m/spl times/900 /spl mu/m/spl times/100 /spl mu/m. It has 41 turns, with coil width of 20 /spl mu/m, space of 20 /spl mu/m, and a high aspect ratio of 5 : 1. The inductance is 0.424 /spl mu/H and the quality factor (Q factor) is about 1.7 at a frequency of 1 MHz. The stray capacitance is approximately zero over the frequency range measured.

Dynamic actuation behavior of NiTi/Si diaphragm micropump

A novel micropump actuated by NiTi/Si diaphragm has been developed. In order to optimize the actuating performance of the micropump, the dynamic actuating properties were studied in different actuating conditions such as different actuating currents, frequencies and duty cycles. The experimental result show that there is a maximum displacement when increasing the actuating current and frequency. The influence of duty cycle on maximum displacement when increasing the actuating current and frequency. The influence of duty cycle on maximum displacement with water flow and without water flow is different. The higher the displacement of the diaphragm is, the larger the flow rate is for a given frequency. The displacement of the pump diaphragm depends not only on the flow rate, but also on the moving frequency. The change of the resistance of NiTi strip indicates that the A - M phase transformation is completed partly during dynamic actuating processes. The maximum flow rate of 360 (mu) l/min was obtained in about 50Hz with 1:1 duty cycle in our experiment.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Surface relief of TiNiCu thin films

TiNiCu thin film shape memory alloys are potential materials for microactuator. In our previous research, the various natural surface relief of crystallized TiNiCu thin film was observed, and it was related with compositions and the sputtering deposition conditions. In order to understand the origin and nature of the surface relief, the temperature-resistance measurement, X-ray diffraction and atomic fore microscopic study were performed. For Ti48.4Ni46.3Cu5.3 thin films, the transformation temperatures are below 0 degree(s)C, and the natural surface is smooth at 12 degree(s)C since the microstructure is austenite. For Ti51Ni44Cu5 thin films, two typical kinds of surface relief, e.g., chrysanthemum and rock candy, were observed at 12 degree(s)C. The chrysanthemum on the martensitic block relief is Ti-rich G.P. zone and will not disappear in thermal cycles later. It is also found that the Ti-rich G.P. zone is related with the thin films formed under lower sputtering Ar pressure. The rock candy relief is a typical martensite surface relief and will disappear when heating to the austenite phase. During crystallization process, the inherent compressive stress introduced under the condition of higher sputtering pressure is helpful to the transition from G.P. zones to Ti2(NiCu) precipitates and the increase of the transformation temperatures.

Structural optimization of NiTi/Si diaphragm used in micropumps

Thin film shape memory alloy microactuators are the promising devices in MEMS. A kind of simple and effective micropump driven by bimorph thin film NiTi/Si diaphragm has been fabricated in our laboratory. This paper presents the optimization of the diaphragm structure with the finite element analysis package ANSYS. Maximum actuation deflections and stress distributions of five kinds of typical structures are analyzed. Simulation results show that patterned NiTi strips should be placed in the center of the silicon membrane to get uniform stress distribution, and there is an optimized distance between the boundaries of NiTi and Si to get maximum actuation deflection. The stress variances of NiTi films and silicon membranes in optimized structure during driving processes are limited in the range of elastic strain, which means the optimized NiTi/Si diaphragm structure has excellent actuation lifetime.

Numerical analysis of a composite diaphragm microactuator

A novel design of a diaphragm microactuator prepared for micropump has previously been reported. The composite diaphragm consists of a silicon membrane and a patterned Titanium-Nickel (TiNi) thin film. In order to understand the actuation behavior of the diaphragm, modeling and thermal simulation of the diaphragm microactuator is performed with commercial finite element analysis (FEA) software ANSYS. In this paper, dynamic temperature distributions in thermal cycles are comparatively studied. During the thermal cycles, temperatures at the center and the border of the diaphragm and in the rounding silicon frames are monitored. The influences of the operational parameters such as current and duty ratio on the temperature distributions are quantitatively predicted. The optimal heating condition for the actuation can be inferred from the simulation results. Futhermore, diaphragm deflection profiles and stress distributions are illustrated by coupled thermomechanical analysis based on the thermal analysis. The experimental measurements of the deflection dependence on various power supplies can be explained in terms of the temperature variations in cycles. Finally, optimization of the patterned TiNi resistance strips is also proposed with respect to uniform temperature distribution and maximum deflection.