Arsenic Prototype 4.0

Principles

The Arsenic prototype v4.0 is the Winter School 2016 kit version of prototype 3.0.

The basis of the prototype remains the same - the bioreporter, a GMO bacteria expressing eGFP (Green Fluorescent Protein) is incubated with a water sample, where the fluorescence is detected optically and can be quantified in order to measure the concentration of Arsenic in the water

• A vial containing the water sample we want to test is positioned on a socket through which a fluorescent excitation LED (blue 488nm for eGFP) 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
• A long-pass filter allow only the signal eGFP fluorescence to reach the photosensor

Moreover, a red LED was added to measure the transmittance, which can be converted into turbidity. The measurement of turbidity will allow us to normalize our results.

• A red LED is placed in-line with the photosensor

With these measures, compared against a standard curve of water containing known arsenic concentrations, one can determine the concentration of arsenic in the sample and so know if the water is drinkable or not.

In summary, the most current version consists of:

   lasercut chassis
   blue LED for eGFP fluorescence excitation at 90 degrees from detector
   red LED for transmittance measurements in line with detector
   vial holder matching the vial approved by the Swiss authorities
   light to frequency detector
   a filter to block excitation light
   LCD screen read out
   based on the arduino

Materials

• Plastic Lens Biconvex (Knight Opticals)
• 510nm long pass acrylic filter (Knight Opticals)

Step by Step Buildling

Laser Cutting Parameters

a chez hackuarium - laser cutter model:

HDF

MDF

Material: particle board HDF (MDF)

	mode	speed	power	scan mode	interval
Groove LED (fluo)	scan	50 (100)	35	x_unilat	0.1
3mm board	cut	15	100
Text and Logo	scan	250 (100)	25	x_unilat	0.3
Groove Lens	scan	50	12	x_unilat	0.1
2mm board	cut	35	100