Microfabricated, silicon spring biased, shape memory actuated microvalve

A microfabricated normally-closed microvalve for air flow has been successfully designed, fabricated and tested. It consists of a flat silicon spring, a co-sputtered and patterned Titanium-Nickel (TiNi) shape memory alloy (SMA) actuator, and an orifice. All three components are batch microfabricated using silicon substrates. This microvalve is designed to be an actuation mechanism for a pneumatically controlled, biologically inspired six-legged microrobot. A TiNi SMA thin film is used as an actuator since it is capable of both high strains (3%) and high forces (work density of 5 × 106 J/m3).; A model is developed to determine device dimensions considering various design parameters. The stroke of the boss is the primary factor in determining the flow rate, and it is closely related to the TiNi SMA thin film stress-strain characteristics and spring constants.; The microvalve components are fabricated using bulk micromachining, co-sputtered thin film deposition, and deep reactive ion etch processes. A plasma dry etch and a XeF₂ etch are both used to repeatably release the TiNi SMA thin films.; Three types of packages have been developed. Two of them are for completed devices, which are two-way and three-way valves. The other is for testing device components. CAD drawings of the packages are downloaded to a computer controlled milling machine which cuts the package components with high precision.; Flow rates of up to 0.5 lpm are achieved when the input air pressure is 245 kPa and the leakage is less than 0.005 lpm, which is the resolution of the flow meter. The microvalve is actuated with 100 mA and the power consumption is 370 mW. The time response of the microvalve is acquired using digital video recording, due to the flowmeter's time response limitations. The on time is about 100 msec and the off time is about 150 msec. The fatigue of TiNi SMA actuator is less than 5% after over 1 million cycles of actuation.