Microfluidic Temperature Control
Various microfluidic applications linked to cell culture or droplet microfluidics are temperature sensitive. Fluigent has developed a microfluidic temperature control solution that can be coupled to a microfluidic system and maintain fluid reservoirs at a desired temperature.
This technology can be integrated in any custom project.
- High performance: stability +/- 0,2°C
- User friendly: easy switch between heating and cooling mode
- Versatile: can be integrated into Fluigent’s protocols and communicate with other modules of a larger microfluidic setup
Microfluidic temperature control: technology description
Fluigent’s microfluidic temperature control module
The temperature controller is based on direct conversion of the electric current into thermal energy. It allows the temperature to be close to 0°C on one side of a thermoelectric device. On the other side, a straight-fin heat sink helps with heat dissipation. The goal of the heat sink is to maximize the surface within a fixed volume to optimize the heat exchange between the device and ambient air. It can be coupled with a fan to be more efficient. Sensors are placed on each side to monitor the temperature change.
Temperature controller: advantages of Peltier elements
The Peltier effect is used as a solid-state method for small temperature lifts in devices called thermoelectric plates or Peltier elements. When DC current flows through, heat is transferred from one side of the device to the other. The scheme below shows cooling functioning. The samples, in contact with the cooled surface, are maintained at low temperatures. On the other side of the device, resistive heating generated by current flow leads to a rejection of heat. 
The use of semiconductors in a thermoelectric plate saves power, as it only uses 10% of the power needed by a traditional air conditioner to provide the same temperature. Moreover, thanks to its compactness and lightweight, it is a well-suited cooling technique for microfluidic applications. Lastly, it is durable, has no mechanical moving parts and does not require contact with fluids. 
Fluigent expertise on microfluidic temperature control equals performance
Stability and accuracy
The use of ventilation enables the temperature control module to reach the set temperature and the use of a PID controller prevents overrunning and oscillations. With the right adjustment of the wind and the control loop’s parameters, after the transition phase, the temperature control module stays within a 0,2°C error margin of the set value.
The set temperature is reached in less than 7 minutes depending on air circulation. Applications usually do not require a specific response time, but it could be improved with greater intensity of the electric current, stronger ventilation and/or the calibration of the PID controller in the microfluidic temperature control module.
Related applications to microfluidic temperature control
- Cell encapsulation
Cell encapsulation is used to improve the recovery of viable cells, a highly temperature-dependent process. As refrigeration is the preferred method for short-term storage of cells, it is crucial to maintain the samples before encapsulation below 5°C during the entire duration of the experiment to preserve them.  Read more
- Live cell imaging
At ambient temperatures, for certain specific experiments, fluorescent microscopy may be affected by photo-bleaching. In this case, this drawback is reduced at low temperatures. The number of photons emitted by fluorescent molecules can also get higher and the signal to noise ratio of fluorescence imaging better. 
Moreover, the ability to quickly and reversibly heat cells helps the study of the cell cytoskeleton, which plays an essential role in several cellular processes, because its dynamic microtubule responds to temperature changes in the range of 2-50°C caused by Peltier elements.  Read more
- Droplet Production
Temperature impacts various parameters during microfluidic-based droplet generation. For instance, the size and frequency of formation of droplets increase with temperature. The regularity of their shape and the flow regime also depends on the microfluidic temperature control of the dispersed and continuous phases.  Read more
- Temperature gradient focusing
With two Peltier elements separated by a small gap, one can create a temperature gradient across a microchannel or a capillary. Combined with an applied electric current and an appropriate buffer, it can concentrate analytes by balancing the electrophoretic velocity of the analytes against the bulk flow. It can also separate them thanks to the electrophoretic velocity gradient generated by the temperature gradient. 
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Expertise and resources
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