Step by Step Guide to Build the Hardware
A bioreactor is a combination of both Electronics, Computer science and Biology. But during experimentation we need to separate them. We thus built a few setup modules for individual devices to be assembled to construct the bioreactor. The constructions have been differentiated as follows:
Pump and Circuit House:
The pumps vibrate due to high friction generated between the plexiglass and ball bearing. To hold the pump tight we need a casing. Since each reactor needs three pumps so we developed a complete box that can hold the pumps as well as the circuit. Even though they are in the same box, they are separated with a middle layer so that it gives extra support to the pumps. A window is made between these two layers for the wires from the pump to reach the circuit. Small windows are also cut on the outer cover so as to connect the individual circuit pins and the USB to the Arduino.
Foundation
The stirring is done using a DC Motor and the principle of magnetic dipoles. Therefore it has to be placed just below the reactor. Aligning the reactor and the DC Motor is very important so that the magnetic stirrer inside the reactor flask can spin with a constant motion. This alignment is achieved by our Foundation structure. It consists of a base plate that holds a simple but strong box like structure. The box consists of different support layers, with three holes, for the motor, each one at a defined gap from each other. The diameter of these holes are the same as the diameter of the DC Motor. These layers allow the DC motor to stand straight and not wobble when switched on. The wiring of the motors is done inside the box with open ended connections coming out of a cut window.
Water Bath
A bioreactor is always maintained at a constant temperature optimum for the growth of the microorganisms, preferably 37 degrees. We achieve this by building our own waterbath using plexiglass. The side walls are cut from a 5 mm thick plexiglass and the base plate from a 2 mm thick plexiglass. This is to decrease the distance between the magnetic stirrer inside the reactor and the magnets attached to the DC motor. The two small side walls have notches with increased length so that the water bath can sit in place on top of our foundation structure described above. The structure consists of two holes on one of the side walls to allow movement of water in and out of the bath from an external heating device. This structure is made water proof using silicon glue.
This structure consists of two levels to help the reactor stand erect and aligned with the DC motor. Just like the motor plates in the foundation structure, these plates have holes with a diameter similar to the diameter of our reactor vessels.
OD And Needle Holder
The bioreactors we use are small flasks with a septum. This septum is pierced with needles to connect it to external fluids or air via the pumps. One of these needles must also be connected through the OD device. This complicated and unsteady outlets are held together and organised by our Holder structure. It is a simple umbrella like structure that sits on the water bath. It has slits through which the needles can come out and still be erect. The OD structure is also held in place between two walls cut out of 2 mm plexiglass.
Files
The Structural Setup of the Bioreactor we developed can be connstructed with just 5 pieces of 5 mm (250x600 mm) and 2 pieces of 2 mm (250x600 mm) Plexiglas. The files for Lasercutting can be found in Aachen_Lasercutter_files.zip