Also discussed here: Detecting gases wirelessly, cheaply (ScienceDaily, Dec.8, 2014)
Today we review a paper that describes the adaptation of a device or “chemiresistors” that had been used to detect chemicals in order to track the progress of new cars and pharmaceutical products during manufacture or provide an alert for explosives . The adaptation means that, without the need for electric power, it can detect gases, such as hydrogen peroxide and ammonia, if they are present within 6 cm and then wirelessly alert a receiver such as a smartphone where the data can be captured an analysed. It makes use of the properties of the sensing metallic surface whose electrical resistance changes with exposure to specific gases. The potential of expanding their use to sensing other gases needs to be examined.
Key Quotes:
“gas-detecting sensors based on devices known as chemiresistors, which consist of simple electrical circuits modified so that their resistance changes when exposed to a particular chemical. Measuring that change in resistance reveals whether the target gas is present…they can detect gaseous ammonia, hydrogen peroxide, and cyclohexanone, among other gases”
“The new sensors are made from modified near-field communication (NFC) tags. These tags, which receive the little power they need from the device reading them, function as wirelessly addressable barcodes and are mainly used for tracking products such as cars or pharmaceuticals as they move through a supply chain, such as in a manufacturing plant or warehouse.”
“the MIT team first disrupted the electronic circuit by punching a hole in it. Then, they reconnected the circuit with a linker made of carbon nanotubes that are specialized to detect a particular gas”
“NFC tags can be read by any smartphone that has near-field communication capability, which is included in many newer smartphone models. These phones can send out short pulses of magnetic fields at radio frequency (13.56 megahertz), inducing an electric current in the circuit on the tag, which relays information to the phone.”
“Current versions of the CARDs [chemically actuated resonant devices] can each detect only one type of gas, but a phone can read multiple CARDs to get input on many different gases, down to concentrations of parts per million.”
"The beauty of these sensors is that they are really cheap. You put them up, they sit there, and then you come around and read them. There's no wiring involved. There's no power,"
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