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OPTICAL SENSORS MAKE ENVIRONMENTAL SENSE

photo - researcher holding photonic sensorResearchers from the Georgia Tech Research Institute (GTRI) patented a photonic sensor in 1990. Today, that work provides the basic technology behind products being produced by Lumense, an Atlanta-based developer of real-time sensors. Photo by Gary Meek.

An optical sensing apparatus and sensing method that offered better stability and lower cost was developed by Georgia Tech Research Institute (GTRI) researchers, Nile Hartman and Dan Campbell, in the late 1980s. By the time the invention was patented in 1990, the research team was already taking its research to the next level. It was developing an integrated optic interferometric sensor that could quickly detect even the smallest amounts of various contaminants in air, groundwater, and food.

The sensor Hartman and Campbell designed was based on laser technology originally conceived for optical communication applications. That technology allows a multichannel micro-sensor fitted with the proper chemical coatings to simultaneously detect multiple contaminants.

The sensor works like this: The speed of light increases or decreases when passing through materials of differing optical properties. Detection of contaminants becomes possible by measuring a contaminant’s influence on the optical properties of the sensor. Then, researchers observe the effects on these properties through changes in the transmitted laser light.

The sensors were integrated into an environmental monitoring system for detecting and analyzing various chemical contaminants, including benzene, industrial solvents in groundwater, explosives, and chemical warfare agents. The system operated in real time to measure concentrations of substances in the parts-per-billion range.

An additional application of the photonic sensor technology was a rapid-response biosensor for detecting microbial contamination, like Salmonella, Listeria, or E. coli, in the water used to wash and chill food. Another biosensor developed at GTRI could detect avian influenza infection in live poultry in just minutes.

The biosensor incorporated integrated optics, immunoassay techniques, and surface chemistry skills. Hartman and Campbell developed it in collaboration with Paul Edmonds, an associate professor of biology at Georgia Tech. After Hartman left GTRI in 2000, Campbell changed the basic design to one he thought was more easily manufactured.

After years of additional development, the general sensing approach has found commercial success with Lumense, an Atlanta-based developer of real-time sensors capable of continuously measuring the concentration of trace chemicals and biologicals in gases and liquids. The company, where Campbell is chief scientist, recently announced that it is shipping a poultry ammonia sensor that provides growers with current, trending, and historical ammonia levels, allowing them to better manage the grow house environment.

— Georgia Tech Research Institute

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