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Principle of our prototype
Our prototype is based on a fluorescent method where we use GMO bacteria expressing GFP (Green Fluorescent Protein) in presence of Arsenic in a water sample. This fluorescence is detected optically and can be quantified in order to measure the concentration of Arsenic.
A vial containing the water sample we want to test is positioned on a socket through which a blue LED passes. GFP absorbs this blue light (λ=475 nm) and emits green light (λ=504 nm) which is detected by a photosensor on which the light is concentrated with the help of two lenses that avoid loss of intensity and that allow more precise results.
Moreover, a red LED was added to measure the turbidity. Turbidity is the cloudiness or haziness of a fluid caused by individual particles. In our case, if there are a lot of GFP, one GFP can absorb light emitted previously by another GFP and then emit light itself and thus creating a chain reaction falsifying the results. The measurement of turbidity will allow us to normalize our results.
With these measures, one can determine the concentration of arsenic in the sample and so know if the water is drinkable or not.