MIT researchers have developed a lightweight toxic gas detector for use with a smartphone, which could potentially help protect soldiers from chemical weapons as well as protect people who work with hazardous chemicals.
The device is sensitive enough to detect less than 10 parts per million of toxic gases within 5 seconds. It is a circuit with carbon nanotubes surrounded by an insulating polymer. The polymer wraps around each of the tens of thousands of nanotubes that make up the device, which separates them, making them resistant to electricity. When the device is exposed to electrophilic, or electron-loving, substances, the polymer breaks down, allowing the nanotubes to join together and increase conductivity. After the electrical resistance goes below a certain level, a near-field communication turns on, sending signals that are detectable by mobile devices with NFC technology.
Electrophilic substances include certain chemicals used in choking agents and nerve gas. In the study, the scientists tested the device on diethyl chlorophosphate, which is a skin irritant and behaves like nerve gas. After 5 seconds of exposure to trace amounts of the gas, the device showed a 20-fold increase in conductivity. It behaved similarly with thionyl chloride, a reactive simulant of choking agents.
“Soldiers have all this extra equipment that ends up weighing way too much and they can’t sustain it,” said Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT, in a statement. “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 readily integrated into a soldier’s uniform that can give them a protective capacity.”
In addition to being lightweight and cheap--each sensor costs about 5 cents to make--the device also works as well as laboratory equipment that is much bulkier and much more expensive. “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,” Swager said.
Next up is testing the device on live chemical agents outside the lab. These will be more dispersed and harder to detect, the team said. They also hope to create a mobile app that will go beyond indicating the presence of a toxic gas and display specific concentrations. This will involve the measurement of the signal strength of an NFC tag, which reflects the resistance of the nanotubes and thus the level of toxic gases in the air.
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