Hardware
The hardware team is working on a bioassay that will be able to maintain the bacteria at optimal conditions for it to grow and, thanks to RFP expression, tell the fishermen the different concentrations of cadmium. The bioassay works by diluting the fish, which dilutes the cadmium as well, to the minimum dilution of cadmium that the bacteria is able to detect. This is done by having five different dilutions being tested at the same time, one dilution per tube, .5 ppm (parts per million), 1 ppm, 2 ppm, 3 ppm, and 4 ppm. In each different volume of liquid the same mass ground fish is placed into the tubes and if the fishmeal has 2 ppm of cadmium the .5, 1, and 2 ppm dilutions will all light up, but 3 and 4 will not, showing that there is only 2 ppm of cadmium, as seen in figure 1.
*Figure 1: Dilutions and Testing
As seen in figure 2 there were multiple requirements that our team needed to uphold. It had to be small and operational in portable conditions. It had to be as cheap as possible while keeping the environment in account, it had to be small and easy to use. It also had to oscillate in order to provide oxygen for the bacteria as well as keep the bacteria heated at 37º C, for optimal bacteria growth. In the end each of these objectives were accomplished with our prototype.
*Figure 2: Requirements for Bioassay
In order to find the proper volume of liquids we had to create an equation that uses the bacterias minimal detection fluorescence, the mass of the fish, and convert the measurement to volume of liquid. The first problem our team had was that the measurement that was tested for the part we were using used mol/L, so we had to also be able to convert from mol/L to ppm due to TASA needing the measurements as ppm. So after due consideration it was decided to base the equation of the conversion of ppm to mol/L, we found a constant and was able to add all our necessary parts in order to create the final equation seen in figure three.
*Figure 3: Final Equation for Dilutions
A prototype of the bioassay has been made and next steps include measuring bacterial growth in the device, printing the parts with a harder plastic, and making a final version. Hardware also needs to create an intensity comparison chart (similar to a pH dipstick) in order for whoever uses the bioassay apparatus can see how intense the fluorescence of the bacteria is and whether it matches the fluorescence that means there is that level of cadmium.
Our bioassay heats and shakes the bacteria for them to grow optimally. This allows larger amounts of bacteria to express RFP in contact with cadmium and thus give a visible marker of what the approximate cadmium concentration is in the fish.
*Figure 3: Final Prototype Picture
*Video 1: Final Prototype Working