Team:Rotterdam HR/Testtubeshaker
Testtubeshaker
Hardware: Test Tube Shaker
The problem
The idea of the test tube shaker came as a result of test where different gas producing bacteria were tested on their gas producing capabilities. As the medium of the bacteria was at rest, most of the bacteria piled up at the bottom. For just the gas production alone had no particular bad results. This behaviour could in the end cause for unwanted results as the bacteria that were underneath the piled up bacteria might not have come into contact with the dissolved carbon monoxide in the medium.
Multiple ideas
As with all problems there are multiple solutions. In this case we came up with three ideas that all had their own
benefits, but in the end one idea was chosen to be used.
The first idea was to just use a magnetic stirrer. The magnetic stirrer is easy in use and is already used for many
laboratory activities. The main downside to using a magnetic stirrer is that it sinks to the bottom. This would mean
that when spun, any bacteria that is stuck underneath the magnetic stirrer would be crushed. Because of this reason
we chose not to implement this idea.
The second idea was quite an innovative one. Because the first idea’s main flaw was that it operated at the bottom, we came with the idea of levitating the magnetic stirrer. After some quick research into levitating a spinning object it became quite clear that this idea was way to complicated for the amount of time left (aprox. 4 weeks). The third idea was again quite a simple one. By just shaking the test tube the desired result would be acquired.
How did we do it?
Because the test tube shaker needed to move and be controlled, we looked into using a motor. We choose a stepper motor for this purpose. A stepper motor is a motor that can be controlled into making a small step with every pulse it receives. This step will be an exact angle and will be specified in the datasheet of te stepper motor, in our case this was 1.8 degrees. We designed and 3d-printed a contraption that could hold the test tube and be connected to the axle of the stepper motor. This design can be seen in the first picture. The second and third picture shows the test tube cap that we design and 3d-printed for the test tube with the caps in the second picture still on the printing bed. These caps let air into the test tube but protect from bacteria that could fall in from above. The video underneath shows the test tube shaker in action.