MEMS-Based System Solutions

Roger Grace

While I—and many others—have waxed eloquent on the subject of microelectromechanical systems (MEMS), this has been a misnomer. Based on my experiences at Sensors Expo, Transducers, MEMS 2009 and the Solid State Sensors and Actuators Conference (frequently referred to as the Hilton Head conference), most of these deal with MEMS devices. If the "s" in MEMS stands for systems then why do MEMS people spend most of their time and effort developing and discussing devices?

The Education Gap
I believe that this is because most universities teach students about devices and their physics, modeling, simulation, design, and behavior. Ph.D. theses are typically about devices rather than practical solutions. As a result, graduating students are not armed with a toolbox of knowledge to create solutions. It is assumed that industry can fill this knowledge gap.

A welcome departure exists at the University of Michigan through its Wireless Integrated Microsystems Laboratory (WIMS) and through the Fraunhofer ENAS Institute in Chemnitz, Germany. Key personnel from these organizations will be the keynote speakers at the Sensors Expo all-day session "MEMS Based Systems Solutions: Thinking Outside the Chip." Professor Thomas Gessner of Fraunhofer and Professor Khalil Najafi from the University of Michigan will share some of the exciting projects that their organizations are investigating to help create commercially viable MEMS-based systems solutions. Professor Gessner is the Chairman of the Smart System Integration Conference to be held on March 10–11, 2009 in Brussels .The conference is an activity of the European Platform on Smart Systems Integration (EPOSS) The European Union has taken a decisive step to fund organizations to undertake work on this effort. This to me is a breath of fresh air.

Think Outside the Chip Various design challenges arise when configuring and integrating a system that has been enabled by a MEMS device. Some of these issues include device integration strategies (monolithic vs. multichip), software codesign/system architecture development, functionality tradeoffs with interfacing circuitry, embedded software to optimize system performance, packaging and interconnects, and system testing and characterization. Just knowing the MEMS device's specifications and characteristics is not sufficient to enable an effective MEMS-based system.

Application Examples
From my recent market research, the MEMS-based systems solutions approach is gaining favor and momentum in the industry. Numerous companies, including Acuity, axept, Crossbow, LV Sensors, and Tronics Microsystems, are pursuing this direction. I consider the tire pressure monitoring systems (TPMS) that are currently invading the automotive market to be the poster child of a successful application of this approach.

Despite the significant downturn of the automotive sector, our market research has pegged this market to exceed 50 million units in 2009. A typical TPMS system similar to the one produced by TRW includes multiple sensors (i.e., a pressure sensor, a motion sensor to control when the device is turned on to save battery life, and a temperature sensor to be used in temperature compensation); a full functioning ASIC that includes power management and stored calibration coefficients; a transmitter/receiver chip to communicate the data to the passenger cabin display, a battery, and an antenna. This is all housed in a robust plastic package that serves as the tire valve stem. It took a great deal of "thinking outside the chip" and the collaboration of many engineering teams at an early stage of the design process to come up with this winning approach. Now isn't this impressive? Especially when the entire solution sells for approximately $5.00 US?

The Way Forward
I believe that the time has come for MEMS-based systems solutions, especially with the current economically trying market conditions. I expect that the adoption of this approach by suppliers will help them to differentiate their products from the current commoditization of MEMS devices. It should also provide the user of the product with a "plug and play" solution in their application and ease in-house system integration efforts. The expected outcome results in a "win-win" approach to doing business.

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