LEDs May Yield Chemical Sensors
MADISON, Wis. -- A class of devices based on LEDs promises to enable the development of cost-effective smart sensors. Researchers at the University of Wisconsin have demonstrated that the chemical sensors, fabricated from standard semiconductor materials, can detect amine gases and sulfur dioxide over a range of concentrations.
The devices offer a number of advantages. "They use very little power," said Arthur Ellis, a professor of chemistry and a member of the research team. "They're lightweight. One could imagine using arrays of these."
The sensors consist of interdigitated fingers of edge-emitting LEDs. The team has used 670- and 890-nm diodes. Half of the fingers are forward-biased and give off light, and the others are reverse-biased and act as detectors. The two are separated by microns.
When exposed to a chemical, the detected light changes according to the concentration of the chemical. The finger design offers a large surface area for increased responsivity. The sensors display a rapid response to a sample, as well as reversibility when the chemical is removed.
Ellis said that the sensors, which the team described in the Jan. 25 issue of Nature, could be modified to detect a wider array of chemicals under a greater range of conditions by coating the sides of the LED fingers with thin films. When exposed to a specific chemical, the thin film would alter the light, creating a chemical-specific sensor. Other coatings might enable the device to function as a sensor for liquid samples, he added.
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