MEMS micro-valves tackle HVAC markets
MEMS microfluidic devices, such as the micro-pumps being designed by Debiotech SA and the micro-valves being hawked by MultusMEMS AB can control micro-litres of fluid- and gas-flows, making them suitable for emerging applications such as medical labs-on-a-chip. Microstaq, on the other hand, uses its MEMS micro-valve technology to control conventional flow applications including HVAC. Recently, a Freescale Technology Forum demonstration featured Microstaq MEMS valve controlling a conventional HVAC system.
Microstaq inserts its tiny micro-valve (bottom) as a pilot into a conventional spool valve (top) to control high-volume flows for heating, ventilation, air-conditioning and refrigeration.
Microstaq earlier reported a collaboration with Freescale Semiconductor Inc. on its intelligent refrigerant control system that employs Freescale's MEMS pressure sensors and MCUs—called Freescale's superheat control module—which now also works with Microstaq's novel MEMS silicon micro-valve.
The micro-valve is made 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, VP of research. "But we can couple that MEMS valve with a conventional spool valve—allowing a micro-valve measuring just 10mm x 5mm x 3mm to control a conventional spool valve that can handle flows into the hundreds of litres a minute."
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 per cent, making the technology good for retrofits. The company 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 today's solenoid valves, for smaller, lighter, and less expensive automatic transmissions to be built, according to the company, which is currently courting automobile transmission makers worldwide.
- R. Colin Johnson
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