Don't Worry The Carpet Is Keeping Watch

TAKE AN ACOUSTICAL PICKUP similar to those in electric guitars. Make it as big as a rug. Result: floors that can sound an alert when a nursing-home patient falls or when a nighttime intruder enters an art museum.

Developed by Messet Oy, a five-person company in Kuopio, Finland, with the Technical Research Center of Finland's VTT Automation Institute in Tampere, the room-size sensors are being tested in nursing homes in Helsinki and Tampere, says Messet Chairman Keijo Korhonen.

The sensor is a thin polypropylene lamination that goes under carpeting or floor tiles. Inside the 0.002-inch-thick structure are tiny pillows of foamed plastic. These function as "electrets," a type of electromagnet used in some microphones. When a weak current is flowing through the top surface, the pillows respond to the slightest changes in pressure by generating an electrical signal. Messet says the structure is so sensitive that it can detect the breathing of a person lying on the floor--through the carpet. Scheduled for a commercial launch next year, the sensor film is expected to cost about $34 a square yard.

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