Reported October 2005

BACKGROUND: Engineers at Carnegie-Mellon University in Pittsburgh have developed a sensor to alert firefighters and emergency responders when it is time to change the cartridge in their gas mask. These teams rely on gas masks to protect them from dangerous toxins.

HOW IT WORKS: The sensor currently under development would be placed inside the respirator's carbon filter and would monitor when it became saturated with dangerous gases. It would act like an "electronic nose," sorting and identifying the chemicals present, because its chip is imprinted with a special conductive polymer coating that is sensitive to differences in chemicals.

E-noses analyze gas samples using an array of electrodes coated with various conducting polymers. After the electrodes are surrounded by the gas, each electrode reacts to a particular substance by changing its electrical resistance. The microchip's neural network then combines all the signals to give a "smell-print" of the chemicals present in the gas mixture. The food industry uses e-noses to detect rotten ingredients, and similar devices are being developed to sniff out specific infections in hospital settings.

WHAT ARE MEMS: Microelectro-mechanical systems (MEMs) integrate electronic and moving parts onto a microscopic silicon chip, making them ideal for new sensor technology. The term was coined in the 1980s. A MEMS device is usually only a few micrometers wide; for comparison, a human hair is 50 micrometers wide. Among other everyday applications, MEMs-based sensors are used in cars to detect the sudden motion of a collision and trigger release of the airbag. They are also found in ink-jet printers, blood pressure monitors, and projection display systems.

The Institute of Electrical and Electronics Engineers, Inc., contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

ECE Department
Carnegie Mellon University
5000 Forbes Ave
Pittsburgh, PA 15213
(412) 268-8443

To learn more about the science of engineering, please contact:

Institute of Electrical and Electronics Engineers, Inc.
1828 L Street, N.W., Suite 1202
Washington, D.C. 20036-5104
(202) 785-0017
http://www.ieee.org
ieeeusa@ieee.org