Smart phones can detect toxic gases read more at here www.spinonews.com/index.php/item/715-smart-phones-can-detect-toxic-gases

Researchers in Japan and US jointly developed a chemical sensing material whose electrical conductivity dramatically increases when exposed to toxic gases. It was demonstrated that this technology made it possible for Smart phones to quickly (in 5 sec) detect toxic gases at a low concentration (10 ppm).

People in today's society are subject to risks of being exposed to toxic gases deriving from natural sources.  The currently available toxic gas sensors are expensive, bulky, heavy and difficult to operate, and it is not practical to set them at many public locations or for people to carry them around.

The joint research group developed a chemical sensing material consisting of a group of carbon nanotubes (CNTs) individually wrapped with supramolecular polymers clusters of monomers held together through weak interactions.

CNTs are highly conductive materials, but when they are wrapped with supramolecular polymers, which serve as insulators, they become poor conductors. The supramolecular polymers were designed weakly bound sites in the molecules are dissociated when these sites are exposed to toxic gases, causing the wrapping molecules to disassemble.

The original high conductive state of CNTs is restored. The extent of change in conductivity is directly proportional to the concentration and the duration of exposure to a toxic gas, and the conductivity change can be easily measured by a commercially available resistance meter.

Toxic gas sensor measurement can be read on smart phones by integrating the chemical sensing material into the electronic circuit.  Users can readily determine the presence/absence of toxic gas by holding an NFC-compatible Smartphone over a sensor-embedded NFC tag while making sure that communication between the two devices is intact.

The sensor is disposable, and 1 g of the chemical sensing material makes 4 million sensors. So, it is feasible to mass-produce the sensor at low cost.

 

This study was conducted at MIT with support from the Postdoctoral Fellowship for Research Abroad program offered by the Japan Society for the Promotion of Science.