A John D. MacArthur Professor of Chemistry at MIT, Timothy Manning Swager has created tiny sensors that detect chemical weapons and explosives but he also sees the potential for the technology to be used in a civilian application: smart food packaging. 
Professor Swager who described Chemosensors as molecule-based devices designed and synthesized to detect a specific chemical signal directed the use of the chemosensory research to harness unique properties of conjugated organic polymers (molecular wires). The research group has demonstrated some years ago that “wiring molecular recognition sites in series” leads to ultra-high sensitivity and that this approach has universal applicability for the amplification of chemosensory responses. The principles developed by their group can amplify chemosensory signals by many orders of magnitude. Their sensor principles are now broadly practiced by many research groups around the world and are the basis of a number or emerging sensor technologies.
With funding from the US Army, Professor Swager, has altered the chemistry in the sensors so that they can detect rotting meat and fruit ripeness. “What I would really like to make is a sensor that can be used in a grocery store to tell if a tomato tastes good,” he says. As part of smart packaging, the business card-sized sensors can be embedded in meat crates being shipped to a grocer. Upon arrival, a worker can scan the shipment with the press of a button to get an instant readout of which crates have questionable contents. “It’s a lot like a passive transponder in your car, which can be powered and read when you drive through the tollbooth,” says Swager.
The sensors’ smarts come from Swager’s combined use of carbon nanotube-based circuitry and radio frequency identification (RFID) tagging technology. When the sensor receives a pulse of power from a remote scanner, electricity flows through the carbon-nanotube circuits. If the target chemical is present, it will either enhance or slow the electron flow and cause a measurable change in electrical resistance. That signal plus the sensor’s RFID tag allow the grocer to quickly locate and cull bad pieces of meat.
Swager sees a range of other potential applications, such as installing fruit ripeness sensors in greenhouses to allow farmers to precisely time harvests and embedding sensors that detect explosives and other harmful agents in public transportation passcards to improve public safety.
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