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Wireless, wearable toxic-gas detector

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MIT researchers have developed low-cost chemical sensors, made from chemically altered carbon nanotubes (CNTs), that enable smartphones or other wireless devices to detect trace amounts of toxic gases.

Using the sensors, the researchers hope to design lightweight, inexpensive radio-frequency identification (RFID) badges to be used for personal safety and security. Such badges could be worn by soldiers on the battlefield to rapidly detect the presence of chemical weapons and by people who work around hazardous chemicals prone to leakage.

“Soldiers have all this extra equipment that ends up weighing way too much and they can’t sustain it,” said Timothy Swager, Professor of Chemistry. “We have something that would weigh less than a credit card. And [soldiers] already have wireless technologies with them, so it’s something that can be integrated into a soldier’s uniform that can give them a protective capacity.”

The sensor is a circuit loaded with CNTs, which are normally highly conductive but have been wrapped in an insulating polymer material that keeps them in a highly resistive state. When exposed to certain toxic gases, the insulating material breaks apart, and the nanotubes become significantly more conductive. This sends a signal that’s readable by a smartphone with near-field communication (NFC) technology, which allows devices to transmit data over short distances.

The sensors are sensitive enough to detect less than 10 parts per million of target toxic gases in about five seconds. “We are matching what you could do with benchtop laboratory equipment, such as gas chromatographs and spectrometers, that is far more expensive and requires skilled operators to use,” Prof Swager said.

Additionally, the sensors each cost around a nickel to make; approximately 4 million can be produced using around 1 gram of the carbon nanotube materials. “You truly can’t make anything less expensive,” Swager says. “That is a method for getting distributed sensing into numerous people’ hands.”

The paper’s other co-author are from Swager’s lab: Shinsuke Ishihara, a postdoc who is also a member of the International Center for Materials Nanoarchitectonics at the National Institute for Materials Science, in Japan; and PhD students Joseph Azzarelli and Markrete Krikorian.

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