Appliance Design - April 2008 - (Page 46)

FLUID HANDLING BIG GAINS FROM TINY VALVE Fig. 1. Microstaq PDA-6 silicon valve. MEMS valve saves energy in appliances. by steve booth and rachid kaina Steve Booth is a co-founder and vice president of marketing, and Rachid Kaina is director of marketing at Microstaq, Austin, Texas. 46 applianceDESIGN April 2008 icro-electromechanical systems (MEMS) have been around for more than two decades. The highest volumes of MEMS devices are sold as inkjet print cartridges and pressure sensors. Recently, high-resolution gyros and angular rate sensors have found application in handheld GPS systems and personal computers. MEMS devices are also found throughout various vehicle systems that control the fuel, engine, and airbag deployment. As with many other technologies, MEMS devices originally developed for the vehicle industry have found application elsewhere. One example is an innovative silicon control valve developed by Microstaq Inc., Austin, Texas. The MEMS valve was invented by mechanical engineers in the automotive industry to advance valve technology in anti-lock braking systems. The design efforts led to a family of proportional silicon valves designed to handle the high pressure (up to 1,500 PSI), high flow (cv: 0.11, 40 slpm N2 @ 10PSID), high temperature (-40 DegC~150 DegC), and harsh environment of a vehicle. Those same characteristics make them suitable for a number of appliance and HVAC/R applications. The silicon valves are easily integrated with pressure sensors and microcontrollers M to form smart, fluid-control modules. The silicon valve can be paired with conventional spool valves typical of hydraulic systems in a pilot/slave arrangement to provide even higher flows. Microstaq currently offers a hybrid silicon and steel spool valve with a 3-mm orifice with a cv of 0.34. The silicon valve is made using standard semiconductor processes augmented with standard MEMS processes in etching and wafer bonding. The valve consists of three layers of silicon bonded together using silicon fusion bonding. The silicon valve includes features that require etching through the entire wafer thickness. Deep, reactive-ion etching (DRIE) is used to accomplish the through-wafer etching in the mechanical (center) layer of silicon where the moving elements are found. The other two layers of silicon act as interface plates to either electrical connections (top layer), or fluid connection ports (bottom layer). Because the valve is completely silicon, materials can be added by vapor deposition to facilitate connection to surrounding components and systems. For example, the center layer gets a metallization deposition www.applianceDESIGN.com http://www.appliancedesign.com

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Appliance Design - April 2008 Contents Editorial Shipments/Forecasts News Watch A Variant of Thermoacoustic Refrigeration Known as Acoustic-Stirling is Expanding Its Range Outside Cryocooling Into More Conventional Applications Such As Refrigeration and Air Conditioning Free-Piston, Stirling Coolers Are Now Showing Up in Mainstream Applications As Costs Come Down and Heat Transport Solutions Are Devised Heat Exchanger Innovations Are Helping To Improve the Overall Efficiency of Vapor Compression Systems Environmental Concerns Have Once Again Ignited a Debate Over Refrigerants A New Glass Ceramic Material for Induction Cooktops Can Be Decorated In a Variety of Glimmering Metallic, 3-D Looks That Can Employ a Number of Shades, Patterns, Styles, Colors, Intensities, and Textures Colorful, Reflective Coatings for Glass Create a Variety of Design Options To Help Designers Establish a Unique Look for Their Products Appliance Designers Faced With Different Motor and Drive Options Need To Understand the Differences and Tradeoffs Before Choosing A New MEMS Valve Offers a Number of Advantages Over Solenoids In Certain Applications, Including the Opportunity To Cut Energy Use The AHR Expo Set Attendance Records and Showcased Thousands of Innovative New Products Classifieds Design Marts Advertiser’s Index Association Report: CEA

Appliance Design - April 2008

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