Wireless badges sense hazardous chemicals

A new wireless hazard badge detects certain dangerous compounds at parts-per-billion levels and warns people of their exposure to these chemicals via smartphone. The inexpensive, battery-free device could find use in chemistry labs and in military settings.

Massachusetts Institute of Technology chemists Timothy M. Swager, Rong Zhu, and Joseph M. Azzarelli developed the device by modifying commercially available near-field communication tags, smart chips that can communicate with cell phones. They added a chemiresistor, made of single-walled carbon nanotubes immersed in an ionic liquid, to the tags (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201604431).

When electrophilic molecules that are chemical warfare simulants hit the ionic liquid coating the conductive nanotubes, the molecules become hydrolyzed, Swager explains. The associated change in resistance in the tag can be detected via a mobile phone. In tests with the nerve agent simulant diethyl chlorophosphate, the MIT researchers showed they were able to detect various levels of exposure to the chemical—from low to moderate to hazardous—over time.

“Today’s cell phones employ more than a dozen sensors for various functions, including detecting light, magnetic field, temperature, acceleration, pressure, and sound waves. But they are all physical sensors,” notes N. J. Tao, director of the Center for Bioelectronics & Biosensors at Arizona State University. “Low-cost and miniaturized chemical sensors, like the one demonstrated by the Swager group, have a huge potential to expand mobile devices beyond tracking of our heart rate or how many steps we walk.”