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This paper presents fabrication, testing, and analysis of a large flow rate microvalve array. The array consists of 88-microvalves fabricated on a silicon-on-insulator (SOI) substrate. The SOI wafer simplifies the fabrication process and eliminates the need for multi-layer surface micromachining process and bulk wafer-bonding procedures. The analytical resonant frequency of the valve is up to 50 kHz and operates at high delta pressures (i.e. 0.14 MPa). The microvalves are fabricated with various flap widths ranging from 300 to 400 μm and flap thickness ranging from 10 to 13 μm. The results indicate that, in terms of geometrical designs, flap displacement and flow rate are strongly dependent on flap thicknesses and to a lesser degree on flap widths. The resonance frequency increases as valve flap thickness increases and width decreases. Comparison between predicted and measured flow rate shows good agreement. A flow rate up to 35 cm 3 /s was measured. A failure criterion is also presented using the fracture stress analysis and shows good agreement with experimental result.

An autonomous flow restricting microthermostat array was successfully designed and fabricated using thin film nickel–titanium (NiTi) shape memory alloy (SMA). The device relies on changes in the environmental fluid temperature for closing without external electric sources. The array of 88 microthermostats was tested at pressures ranging from 6.9 to 34.5 kPa and water temperatures of room temperature and 80 °C. At 34.5 kPa and room temperature, the flow rate was 722.8 ml/min. As the temperature of the water increased to 80 °C, the flow rate was reduced by 90% depending on the pressure. Finite element predictions are in relatively good agreement with the measured flow rates.

In this paper, thin film (10 μm) nickel–titanium (NiTi) shape memory alloy (SMA) was used to develop a compact actuator pump generating high output force at large velocities. The velocity was dependent on actuation frequency of the thin film NiTi membrane operated at 10, 50, and 100 Hz. The liquid flow also provided forced convection cooling of the NiTi membrane. The inlet and outlet pressure were always at equilibrium prior to actuation and the inlet pressure biased the NiTi membranes. Experimental results show that the optimum operating output load was 98 N, and the blocking force was 198 N. The peak velocity of 5.85 mm/s (2.96 cc/s) was obtained while operating the membrane at 100 Hz. Analytical predictions provide general trends observed experimentally. Actual measurements were smaller than predictions (i.e. peak velocity of 13.9 mm/s which corresponds to 7.03 cc/s) due to assumed constant pressure in the model.

A robust passive high frequency high pressure micro check valve was developed for piezoelectrically actuated pumps. A novel cross-patterned microvalve flap is used to increase the valve’s structural stiffness with pressures up to 10 MPa. A mechanical valve stopper prevents valve-flap failure under extreme high pressure. The valve-flap is also designed to work at frequency larger than 10,000 Hz. The valve-flap was fabricated with electroformed nickel on silicon substrate. Deep RIE etching was used to fabricate the valve channels in the silicon substrate. The whole valve weighs 0.2 g including packaging. The microvalve flow rate (water) is measured to be 18 cm3/s under a pressure difference of 50 psi. The microvalve was integrated with a compact piezoelectric pump and produced pressure of 350 psi when operated at 10 kHz frequency.

The frequency response of thin film nickel–titanium (NiTi) shape memory alloy (SMA) membrane in three fluid mediums (air, silicon oil, and de-ionized water) was investigated in the present paper. Operation was investigated at different power input and duty cycles. Results showed an operating frequency of 40 Hz could be achieved in de-ionized water with appropriate power input and duty cycles. Larger operating frequencies could be achieved by applying power over a short heating time to minimize the temperature rise in the surrounding fluid. Results demonstrated the extreme sensitivity of frequency to operating medium, power input, and duty cycle. That is, changing one of these parameters, the frequency response could be changed by an order of magnitude.

The design, fabrication, and testing of a compact displacement accumulation device is presented in this paper. The piezoelectric device provides both large displacement (mm) and large force (100 N). The device is based on conventional inchworm motor design that produces large displacement. The device integrates piezoelectric stacks for large force output and high-speed operation with MEMS ridges as a new clamping system. The device should be able to push and pull 450 N at 11 mm/s in a relatively compact size. FEM analysis is used for the design, EDM is used for the fabrication of a prototype, and conventional test techniques are used to evaluate performance. Stress and modal analysis are used to confirm that the device has an infinite fatigue life and a first modal frequency at 1309 Hz. Experimental data for clamping strength of the ridges and blocking force of the device validate that the device transfers the required load of 450 N. The device is successfully tested over a wide range of operating conditions at speeds up to 11 mm/s using open loop control. The stall load of the device is measured to be exceeding 2250 N. For the dynamic loading test, the device pushes test weights up to 50 N with the open loop control approach.