Arsenic Prototype 4.0
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
You can find the bill of materials here:
Step by Step Buildling
All files can be found here:
Laser Cutting Parameters
at chez hackuarium - laser cutter model: Keyland KQG-1060 120W CO2 laser cutter
|Groove LED (fluo)||scan||50 (100)||35||x_unilat||0.1|
|Text and Logo||scan||250 (100)||25||x_unilat||0.3|
Assembling the Electronics
There are four PCBs for:
- Blue LED (for the eGFP excitation)
- LCD screen
- Red LED (for the transmittance)
- Light to frequency meter (to detect the light)
Soldering and Mounting
light to frequency meter
Finally, the Red LED and light to frequency meter will be plugged into the Blue LED board with connectors.
Then the LCD screen is plugged into the Blue LED board with a ribbon cable.
The LCD screen board is ready to be mounted on the arduino.
We are now ready to test it out.
Testing the Prototype
Links other References