MEMS Applications

Imagine dust, floating in the air, gathering information on the weather, winds, humidity and pollution – all in a tiny cubic millimeter package. This is the “smart dust” scientists at UC Berkeley are developing in the laboratory today. Thousands or millions of these dust motes will sense the environment and communicate simultaneously using MEMS devices. Other applications under development range from such medical uses as hospital rooms that track patients and their medications and treatments, to the use of tiny surgical “scrapers” injected into arteries to clean out plaque, to military reconnaissance, to the detection of biological and chemical weapons.

Automotive: the first high volume application
After spending about 25 years in the lab, however, it was the automotive industry which first commercially embraced MEMS devices in the '90's as airbag accelerometers, recognizing the benefits of MEMS devices' small size, relative low cost and high degree of sensitivity.

Early airbags required the installation of several bulky accelerometers made of discrete components mounted in the front of the car, with separate electronics near the airbag (at a cost of over $50). Today, because of MEMS, the accelerometer and electronics are integrated on a single chip at a cost of under $10. The small size (about the dimensions of a sugar cube) provides a quicker response to rapid deceleration. And because of the very low cost, manufacturers are adding side impact airbags as well. The sensitivity of MEMS devices is also leading to improvements where size and weight of passengers will be calculated so the airbag response will be appropriate for each passenger.

There are many other automotive applications for MEMS either in use now or coming soon, including fuel pressure sensors, air flow sensors, tire pressure sensors with automatic built-in tire pumps, “smart” sensors for collision avoidance and skid detection, “smart” suspension for sport utility vehicles to reduce rollover risk, automatic seatbelt restraint and door locking, vehicle security, headlight leveling, and navigation.

MEMS come of age
Another wide deployment of MEMS is their use as micronozzles that direct the ink in inkjet printers. They are also used to create miniature robots (micro-robots) as well as micro-tweezers, and are used in video projection chips with a million moveable mirrors.

MEMS have been rigorously tested in harsh environments for defense and aerospace where they are used as navigational gyroscopes, sensors for border control and environmental monitoring, and munitions guidance. In medicine they are commonly used in disposable blood pressure transducers and weighing scales.

Out of these practical experiences have grown a raft of other applications which are quickly approaching everyday use. For example, engineers are utilizing the ability of MEMS devices to collectively assemble information and applying it to “smart roads.” Smart roads would be covered with millions of MEMS sensors. The sensors would act as a blanket of information, gathering and transmitting data about road conditions to people charged with maintaining them. Problems with roadways would be detected and repaired before they became serious. These smart roads could also send information to cars equipped with Global Positioning Devices, informing the on-board computer of road hazards, accidents, and traffic. Another safety application includes the detection of black ice on roadways and the development of windshields with automatic glare resistance.

Other arenas into which MEMS are moving include package shipping, where MEMS shock sensors would rest inside packages to monitor time and any type of damage that may occur while the package is in transit. One commercial application that is coming to market within months is a compact skin analysis unit for medical and consumer use, including department store cosmetics counters and pharmacies. This tool will contain small sensor-based units to analyze the physical and chemical properties of skin surfaces.

An additional and significant growth area for MEMS today is in telecommunications where the technology is being used for wireless applications as well as in optical networks.