for National Geographic News
A terrorist enters a busy airport carrying hidden explosives. But he doesn't get far. Micro-sensors embedded in the airport's ventilation system immediately detect the explosive vapor in the air, alerting security.
This could be the future in the battle against terrorismand it may be closer than you think, thanks to new explosives detection technology. Researchers from the University of Nevada in Reno and Oak Ridge Laboratory in Oak Ridge, Tennessee, have developed a miniature cantilever that can sense TNT vapor and distinguish it from non-explosive vapors.
Conventional sensorslike the detection machines used in airportsare expensive and bulky. Until now, dogs have been the most effective explosives detectors. But canine detection has practical limitations; dogs can only be in one place at a time.
On the other hand, the new explosive-vapor sensorsor miniature mechanical noses, if you willhave a detection capability that may surpass that of dogs. Perhaps more importantly, the devices could be used on a large scalein airports, office buildings, even restaurants.
"These self-sensing micro-cantilevers are 10,000 times smaller than current explosives detection technology, consume 10,000 times less power than other micro-cantilever technologies, and when mass fabricated could reach a price point 100 times lower than what is on the market today," said Jesse Adams, an assistant professor of mechanical engineering at the University of Nevada in Reno, who developed the sensors.
The research is described in tomorrow's issue of Nature.
Setting Off Explosions
Here's how it works. The micro-cantilever has two integrated elements, both smaller than an ant's eye. One is a combined sensor and actuator to both sense and create reference motion, and the other is an integrated heating element that can raise the temperature of the cantilever by hundreds of degrees Celsius in less than a second.
When the device catches tiny particles of an explosive from the air, an integrated heater on the micro-cantilever triggers miniscule quantities of explosive material on the surface of the device.
"We're detecting the presence of the explosive on the micro-sensor by actually causing a small explosion on the sensor," said Adams.
While the sensors are able to detect a miniscule amount of explosive vapor, they can distinguish it from non-explosive vapors.
The idea of using micro-cantilever sensors to detect explosives is not new. But previous technology has struggled to integrate a sensor and an actuator. Sensing still usually requires external optics, like lasers and photodiodes. There were also difficulties with high power consumption, and figuring how to use many cantilevers at a time.
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