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Chemical Sensor for Smartphones Wirelessly Detects Hazardous Gases

MIT chemists have devised a new way to wirelessly detect hazardous gases and environmental pollutants, using a simple sensor that can be read by a smartphone. The inexpensive sensors could be widely deployed, making it easier to monitor public spaces or detect food spoilage in warehouses. The researchers have demonstrated that they can detect gaseous ammonia, hydrogen peroxide, and cyclohexanone, among other gases. For several years, the lab of professor Timothy Swager has been developing gas-detecting sensors based on chemiresistors, which consist of 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. Unlike commercially available chemiresistors, these sensors require almost no energy and can function at ambient temperatures. 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. To adapt these tags for their own purposes, the MIT team disrupted the electronic circuit and then reconnected the circuit with a linker made of carbon nanotubes that are specialized to detect a particular gas. The team refers to the modified tags as CARDs: chemically actuated resonant devices.

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Computers Defense Detectors Electronic Components Electronics & Computers Materials Monitoring RF & Microwave Electronics Semiconductors & ICs Sensors Test & Measurement

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    Transcript

    00:00:05 What if you could determine if the fruit is ripe, if there is a hazard in the air or even diagnose disease with a smartphone. Our research is focused on making this possible. The wireless chemical sensor that we create has an embedded nano-material that is capable of interacting with a chemical.

    00:00:22 And that interaction leads to a change in the wireless communication between the sensor and the phone. To do this we're combining near-field communication technology already embedded in modern smartphones with wireless chemical sensors. First we modify the RF ID

    00:00:41 tag by cutting the electrical circuit. We then recomplete the circuit using our pencil to draw a wire but this pencil is far from ordinary. The graphite has been replaced with a carbon- nanotube based material that we have programed for detection of a specific chemical. Because of the electrical behavior of the

    00:00:57 pencil material the current over this wire changes in the presence of the chemical we want to detect. When we read the sensor with our smartphone it signals whether the chemical is present, or not. A unique feature of this technology is that it makes it possible to gather chemical information in a non line-of-sight

    00:01:14 type of fashion such as through a box or through walls. So that the user does not have to come in contact with a chemical. Ultimately we are excited this technology enabling the consumer to collect information, on their own, about their local chemical environment.