Hardware
What is our prototype?
It is a tri-compartment battery containing two types of genetically modified bacteria. These bacteria, through a production and degradation mechanism, will produce electrons that generate an electric current. The aim of our prototype is to create a small-scale battery that can use this current and/or measure it. This will allow us to start on a viable basis before industrial scale.
What were the issues to be considered for the prototype?
Size change
After various tests and measurements on an old prototype. The voltage is correct and measurable, but the current is still too low. Because it is limited by the production speed of bacteria. The prototype improves the low intensity by increasing the size. The larger the container, the more bacteria can be grown and the more current they can produce.
We have increased the size of the container to 500mL for each bacteria.
Culture liquid replacement
We have included four inlet and outlet valves on the side to renew the culture liquid for each bacterium.
Sizing
We designed the prototype to optimize the current produced. To do this we designed the tanks to be wide and high but short in length. With flat anodes covering the entire height of the tank. The distance between the edge of the tank and the anode is small enough to limit electron losses and obtain a more powerful current.
Moreover, by having shorter tanks, the distance between both anodes is reduced while the volume has been multiplied by 10. Again, the shorter the distance, the easier it is for the current to flow through the culture medium.
Hermeticity
Like chemical batteries, it must be hermetic for safety reasons. Not for toxic risks but for bacteriological risks. Indeed, devices using bacteria must be isolated from their environment by layers. The shell is one such layer, as is the extractor hood where the prototype and the laboratory are placed. We added seals on the flat surfaces. The system closes with nuts on the top.
Optimizing anodes
The anodes are pierced in order to facilitate the homogenisation of the medium and to favor exchanges between the tanks. For cost reasons we preferred a raw aluminium anode rather than a gold one. We keep an excellent conductivity and a limited oxidation. More performing materials like copper or silver are bactericidal materials.
Choice of materials and printing
We chose to manufacture our prototype using a 3D printer. The plastic material is strong enough and safe for the bacteria.
Moreover, printing our prototype allows us to correct defects and test different solutions.
