Ultra low cost LED based gas sensing
Orpen, Dylan and Fay, Cormac and Beirne, Stephen and O'Toole, Martina and Lau, King-Tong and Corcoran, Brian and Diamond, Dermot (2011) Ultra low cost LED based gas sensing. In: Photonics Ireland 2011 , 7-9 Sept 2011, The Grand Hotel, Malahide, Dublin..
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Over the last number of years a movement has taken place where conventional point-to-point grab sampling style sensors have slowly been phased out in favor of in situ autonomous sensors. Autonomous sensors provide a better insight into the monitored parameter delivering more data points in a less manual fashion. Over the next ten years, it’s predicted that gas sensors will become smaller, consume less power and exhibit much improved performance, and be of substantially reduced cost . Optical sensors certainly are in pole position in terms of development having already met many of the criteria.
The authors present a low cost (< €1) sensing platform. Two L.E.D’s are setup as a light sensor (emitter,detector), where the light passing from the emitter to detector L.E.D is modulated by a chemically selective colorimetric film, providing an indirect chemical measurement (this sensing setup is visible in Figure 1). Our presented experimental setup has exhibited a limit of detection in the p.p.b region (0.001145 mg/L or 12 ppb) , as well as demonstrating a 95% recovery within 30 seconds of contaminant exposure  (example exposures visible in Figure 2).
This work has been done utilizing a bromophenol blue based dye, which was inkjet printed to created reproducible optical pH sensitive slides. However, the target of the device can be tuned by varying the colorimetric coating composition.
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