MicroElectroMechanicalSystems [quite different from memes which we covered earlier]. MEMS rhymes with “hems” if you are into sewing or “Dems” if you are into abbreviated US politics. They are the new wave of highly miniaturized sensors and actuators that bring ‘intelligence’ to many of our portable devices by monitoring and reacting to physical conditions. They are built on silicon wafers, typically in the micrometer or millionth-of-a-meter size range. They often use photolithographic techniques just like integrated circuits. The Nintendo Wii video game system is one example of usage. It relies on MEMS to translate your hand motions to actions on a video screen. Table tennis, golf, archery, skiing, exercising to a virtual instructor and many other activities are available for the Wii, with MEMS as the link between actual and virtual reality.
iPhones, iPads and similar devices use MEMS to sense when the display should go from vertical to horizontal as you tilt the device sideways. There are children’s games and eBooks that rely on motion (see the Alice application for an iPad as an extreme example) just as there are MP3 players that switch songs when you shake the player. But there are more subtle uses of MEMS also. Your cell phone turns off its display when you lift it to your ear, saving on battery life. Many laptops (and iPods) have sensors that detect being dropped to prevent hard disk damage. Cameras offer image stabilization for better pictures, counter-acting your shaky hands. Airbag deployments rely on micro accelerometers for early detection of a car accident so you can be buffered from the impact. Other uses in an automobile include auto-tilting of headlights with terrain changes. The BMW X5’s suspension and handling also adjust to what the MEMS are saying about the road. Then there is tire-pressure monitoring, auto-tensioning of seat belts, and so on, plus the gyro-sensor in GPS units.
Medicine has been a major beneficiary of MEMS. Pressure, flow and optical sensors are finding uses in miniaturized insulin delivery systems, better control of drug delivery in inhalers, better hearing aids, improved sleep apnea masks, improved pace makers and the like. On the cutting edge are sensors that can tell the pressure on an aortic wall, digestible pill-cameras that relay “inside information” on their journey and lithium sensors to aid in managing bi-polar dipolar disorders.
These systems on a chip allow combining computational “brain power” with the “five senses” to make possible ever-smarter technology. So what’s next? One area of focus is human clothing. MEMSwear-1 was a National University of Singapore project that started with the ability to detect and prevent elderly patient falls. MEMSwear-2 is looking to use clothing to monitor vital signs for patients using distributed sensors and Bluetooth to relay the information to caregivers and family members. NASA has a similar need to monitor vital signs for astronauts and has developed LifeGuard. The military, too, is interested in how clothing can adapt to various conditions. Beyond self-adjusting camouflage, adjusting to soldier’s body temperature and the ambient conditions, there are also things like a sleeve becoming a stiffened splint if the arm is hurt and needs support.
Intrigued? You can visit Wikipedia for a manufacturing-oriented posting on MEMS. Sandia National Labs has an MEMS image gallery that show things like the size of a dust mite in comparison with MEMS gears. MEMSnet is a portal that gives you news and links to other resources.