Difference between revisions of "Team:Grenoble-Alpes/temperature module"

TEMPERATURE MODULE

• PROJECT
  • BIOLOGY
  • ENGINEERING
    • PIPETTING MODULE
    • FLUORESCENCE MODULE
    • TEMPERATURE MODULE
    • PURIFICATION MODULE
  • DEMONSTRATE

In the automated system, many steps require to heat or cool biological samples. Typically, the biological transformation is a good example: the samples containing the bacteria and the DNA need to be heated and cooled for precise durations at a constant temperature to realize a heat shock (a classical transformation goes from 0°C for 30 minutes to 42°C for 1 minute and back at 0°C for 2 minutes). Hence, this module has to be carefully considered because it is a key point to the success of any biological manipulation. In addition, because our system will be fully automated and nobody will be able to check the inside of the machine while it works, a reliable and robust module is required so that each time it is used, repeatable results are obtained.

In the following figure, the different biological steps are summarized and their required temperatures are given.

By design, each biological step will be contained in a module with a given temperature. This allows us to make temperature shocks by pipetting the liquid inside an Eppendorf tube from one place with a given temperature (0°C for instance) to another place in the machine with another temperature (42°C this time).

Design of the module

An Infra-Red temperature sensor placed on top of the Eppendorf tube can continuously sense the temperature of the solution from a distance (without disturbing or contaminating it) and send it to an Arduino.

A thermal conductor, placed around the tube and in contact with the heating/cooling device, eases and homogenizes the heat/cold transfer between the Eppendorf tube and the device producing heat/cold (to better homogenize the solution, an electronic pipette can also flush the solution).

The device in charge of heating/cooling the solution is placed under the Eppendorf tube. It is activated with the help of an Arduino and a MOS transistor. A goal temperature is programmed [1] in the Arduino and the heating/cooling device is switched on/off to be kept at this goal temperature (this way of programming the heating/cooling device powering is called an “all or nothing regulation”).

Temperature tests

In the following part, measurements of the temperature inside an Eppendorf tube placed in the modules were made to characterize them.

The cold module

The temperature inside a tube placed in the module (red curve) was measured and compared to the evolution inside of an ice tank (green curve).

During the test, we were only able to make the module go down to only +11°C. The main explanation would be that 2 Peltiers modules are not enough to cool down eight Eppendorf tubes at the same time. The Peltier modules are still capable of cooling the tubes from 27°C to 11°C (16°C difference).

However, the slope is quite similar for both curves. The 8 solutions still undergo a rapid change of temperature that can be considered as a temperature shock and might be enough for the success of a bacterial transformation. The effectiveness of it will have to be further tested. Also, because obviously this system will never reach 4°C (the goal temperature at which it should be powered-off by the all or nothing loop), the system is continuously powered so it doesn’t risk a degradation and the temperature will stay constant on its own. No variations to potentially disturb the bacteria.

        The other interesting information here is that it takes 10 minutes (600 seconds) for the module to get to its lower temperature. Hence, before any manipulation, the user will have to power-up the machine at least 10 minutes before using it.