An optical sensing apparatus and sensing method that offered better stability and lower cost was developed by GTRI researcher, Nile Hartman, in the late 1980s. The invention was patented in 1990, but Hartman was already taking his research to the next level. He was developing an integrated optic interferometric sensor that could quickly detect even the smallest amounts of various contaminants in air, soil, groundwater and food.
Hartman's sensor was developed from laser-based technology originally conceived for optical communication applications. That technology allows a multichannel microsensor fitted with the proper chemical coatings to simultaneously detect multiple contaminants.
It 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 called E-SMART. The system detects and analyzes various chemical contaminants, including heavy metals, solvents, petroleum oil and lubricants. E-SMART operates in real time and measures very small amounts of contaminants.
An additional application of the photonic sensor technology is a rapid-response biosensor for detecting microbial contamination in food, particularly poultry. For example, a biosensor developed at GTRI can detect avian influenza infection in poultry in just minutes.
The biosensor incorporates integrated optics, immunoassay techniques and surface chemistry skills. Hartman developed it in collaboration with Paul Edmonds, an associate professor of biology at Georgia Tech, and Dan Campbell, a GTRI research scientist.
In 1997, Hartman’s work reached a major milestone when it was patented by Hartman and the Georgia Tech Research Corporation. Subsequently, the sensor was licensed commercially by the Atlanta-based company, Photonic Sensor.