Arsenic Prototype 1
This is the beginnings of the Arsenic detector prototypes - Arsenic Prototype 1 within the full Chronology of the prototypes. This version was developed at EPFL in 2013, and is part of their 2013 Final Report.
For our first prototype, we decided to remain open to either Arsenic or E.Coli detection. We did background research on different methods, to have a panel of what was available and matched our criteria. We wanted to create a device open-source, not too expensive, easy-to-use and portable.
From all the methods we found, we chose fluorescence, which seemed to be the easiest technique to take out of the lab and allowed to detect both Arsenic and E.Coli.
A typical fluorometer looks like that :
The fluorescence is measured at an angle of 90° from the light source.
The light from the LED passes through a lense to be focused and then through a filter, to only let the excitation wavelength pass through. That filtered light will excite the sample, which will emit at another wavelength and will then be detected. In general, photodiodes or photomultiplier are used as detectors, but they are quite expensive. That is the reason why we looked for an alternative : a digital camera. Indeed, all camera contains an RGB filter, which can be used to detect only the range of wavelength we want to detect. And for the LED, we used one that emits at the range of excitation wavelength we needed, so we could eliminate the filter from the list of elements to purchase.
For the actual prototype, we first used two paperboard boxes sticked together with two holes for the camera and the LED. The box is closed so no external light would disturb the measurement. Inside, there is a horizontal place for the sample-holder and ouside we used an Arduino as the LED current source.