MEMS microfluidic devices, such as the micro-pumps being designed by Debiotech S.A. (Lausanne, Switzerland) and the micro-valves being hawked by MultusMEMS AB (Uppsala, Sweden) can control micro-liters of fluid- and gas-flows, making them suitable for emerging applications such as medical labs-on-a-chip. Microstaq (Austin, Texas), on the other hand, uses its MEMS micro-valve technology to control conventional flow applications including HVAC and automatic transmissions on cars.
Microstaq previously announced a collaboration with Freescale Semiconductor Inc. on its intelligent refrigerant control system that employs Freescale's MEMS pressure sensors and microcontrollers—called Freescale's superheat control module—which now also works with Microstaq's novel MEMS silicon micro-valve.

The Microstaq's micro-valve is fabricated using the same silicon processing steps as an ordinary chip--layers of patterned silicon—but with micron-sized channels through which the fluid or gas flows. By using the precision MEMS valve as a pilot for controlling conventional valves, even high-flow applications can be micro-managed by MEMS, according to MicroStaq.

"Our micro-valve is fabricated from three layers of silicon, the central layer of which is a mechanical element that moves through electrically controlled thermal expansion to open and close a microfluidic port," said Nelson Fuller, vice president of research. "But we can couple that MEMS valve with a conventional spool valve—allowing a micro-valve measuring just 10-by-5-by-3 millimeters to control a conventional spool valve that can handle flows into the hundreds of liters a minute."

For the last two years, Microstaq has been advising potential customers that switching to its micro-valves can increase the efficiency of existing HVAC systems by as much as 25 percent, making the technology good for retrofits. Now Microstaq has started landing contracts to retrofit MEMS valves into commercial refrigeration systems, starting with grocery store chains.

Besides HVAC and refrigeration applications, Microstaq is also pioneering the use of MEMS micro-valves for transmissions in automotive applications. MEMS valves take up three times less space than the solenoid valves used today, enabling smaller, lighter, and less expensive automatic transmissions to be built, according to Microstaq, which is currently courting automobile transmission makers worldwide.