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Revision as of 12:00, 17 October 2018
Template loop detected: Template:Grenoble-Alpes
TEMPERATURE MODULE
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.
![](https://static.igem.org/mediawiki/2018/8/83/T--Grenoble-Alpes--temperatureFig1.png)
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
![](https://static.igem.org/mediawiki/2018/c/c9/T--Grenoble-Alpes--temperatureFig2.png)
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 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).
![](https://static.igem.org/mediawiki/2018/4/41/T--Grenoble-Alpes--temperatureFig3.png)
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.
The heating module
![](https://static.igem.org/mediawiki/2018/c/c8/T--Grenoble-Alpes--temperatureFig4.png)
The heating module works in the same way as the cooling module but the temperature is taken inside an empty Eppendorf tube so that the whole environment is at the goal temperature and not the liquid inside of the tube.
A goal temperature is set (42°C here) and the evolution was plotted in the previous figure. It takes about 15 minutes for the module to go to 42°C and once it has reached the goal temperature, the power turns off for a little bit of time, causing the temperature to drop again to 37°C. This shows an inaccuracy of the temperature of about 5°C that could be problematic if we heated the solution for a longer time at 42°C (which is not the case because in a bacterial transformation, the tubes are heated for about one minute).
Moreover, when we put an Eppendorf tube filled with liquid inside the module, the IR sensor will measure that the solution is under 42°C and power-on the module so that the temperature will immediately go up. In the end, when the tube is put inside of the module, the temperature is always between 40°C and 42°C, which is a better accuracy.
![](https://static.igem.org/mediawiki/2018/9/9b/T--Grenoble-Alpes--temperatureFig5.png)
In the case of a goal temperature of 70°C, the heating resistor powered by a 12V supply is only able to heat-up the whole aluminum block to 70°C +/- 2°C. Hence, the control loop will rarely be triggered and the temperature will stay constant on its own at 70°C.
Moreover, it is interesting to see that for any step requiring a temperature àf 70°C, the module needs to be started 7 minutes beforehand to get to the right temperature.
How to build the modules ?
LEARN MORE
REFERENCES
[1] S H Price (26 March 2007), “The Peltier Effect and Thermoelectric Cooling” consulted in May 2018 on http://ffden-2.phys.uaf.edu/212_spring2007.web.dir/sedona_price/phys_212_webproj_peltier.html
[2] G. Ya. Karapetyan and V. G. Dneprovski (January 2003) Book “Research of opportunity to use mism structures for cooling of light-emitting diodes” consulted in May 2018 on https://www.researchgate.net/publication/258436493/download
[3] Omron Industrial Automation website, FAQ entilted "Temperature Controller: Hysteresis" consulted in May 2018 on http://www.omron-ap.com/service_support/FAQ/FAQ00549/index.asp
[4]Picture from https://nl.aliexpress.com/item/Four-heat-pipe-CPU-Cooler-Heatsink-for-Intel-LGA1150-LGA1151-LAG1155-LAG775-LAG1156-AMD-FM2-FM1/32513602134.html
[5] DBK Technology Ltd (2004), “ΩDBK HPG Series PTC Heaters” consulted in July 2018 on https://docs-emea.rs-online.com/webdocs/0f72/0900766b80f72deb.pdf
[6] On semiconductors (November 2014) “Plastic Medium-Power Complementary Silicon Transistors” consulted in June 2018 on https://www.onsemi.com/pub/Collateral/TIP120-D.PDF
[7] Siemens “BUZ 100 SIPMOS Power transistor” consulted in June 2018 on http://www.datasheetcatalog.com/datasheets_pdf/B/U/Z/1/BUZ100.shtml
[8] Melexis (June 29, 2015), “MLX90614 family Single and Dual Zone Infra-Red Thermometer in TO-39” consulted in May 2018 on https://www.digikey.fr/product-detail/fr/melexis-technologies-nv/MLX90614ESF-BCF-000-TU/MLX90614ESF-BCF-000-TU-ND/3641020