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.
Benefit from the best performance and Fluigent expertise for your 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
Fluigent microfluidic temperature control module

Microfluidic temperature control: technology description

Fluigent’s microfluidic temperature control module

Operating principle of the microfluidic temperature control solution
Fig 1: Operating principle: the temperature control module can heat or cool depending on the instruction and interact with other modules thanks to its integration into the software

The temperature controller is based on direct conversion of the electric current into thermal energy. It allows to keep the temperature close 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.

Integration of the microfluidic temperature control module
Fig 2: Example of Fluigent’s microfluidic temperature control module that can be integrated into a microfluidic system

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. [1]

Peltier microfluidic temperature control
Fig 3: Functional diagram of a thermoelectric module

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. [2]

Fluigent expertise on microfluidic temperature control equals performance

microfluidic temperature control after transition phase
Fig 4: Temperature measured after the transition phase, for a setpoint value of 5°C

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.

Response Time

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.

Microfluidic temperature control results without PID
Fig 5: Testing different fan speeds for a setpoint value of 2°C for the cold part without PID controller
Microfluidic temperature control results with PID
Fig 6: Testing different fan speeds for a setpoint value of 2°C with PID controller

Related applications to microfluidic temperature control

  • Cell encapsulation

Cell encapsulation involves microfluidic devices and 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. [3][4] 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. [5][6]

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. [7][8][9] 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. [10][11] 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. [12][13]

References

[1] S. B. Riffat, X. Ma, “Improving the coefficient of performance of thermoelectric colling systems: a review”, International Journal of Energy Research, 2004

[2] S. Kumar, A. Gupta, G. Yadav, H. P. Singh, “Peltier Module for Refrigeration and Heating using Embedded system”, International Conference on Recent Developments in Control, Automation and Power Engineering, 2015

[3] S. Swioklo, A. Constantinescu, C. J. Connon, “Alginhate-Encapsulation for the Improved Hypothermic Preservation of Human Adipose-Derived Stem Cells”, Stem Cells Translational Medecine, 2016

[4] A. Z. Khan, T. P. Utheim, C. J. Jackson, K. A. Tonseth, J. R. Eidet, “Concise Review: Considering Optimal Temperature for Short-Term Storage of Epithelial Cells”, Frontiers in Medecine, 2021

[5] J. S. H. Danial, Y. Aguib, M. H. Yacoub, “Advanced fluorescence microscopy techniques for the life sciences”, Global Cardiology Science & Practice, 2016

[6] R. Kaufmann, C. Hagen, K. Grünewald, “Fluorescence cryo-microscopy: current challenges and prospects”, Current Opinion in Chemical Biology, 2014

[7] G. Velve-Casquillas, J. Costa, F. Carlier-Grynkorn, A. Mayeux, P. T. Tran, “A Fast Microfluidic Temperature Control Device for Studying Microtubule Dynamics in Fission Yeast”, Methods in Cell Biology, 2010

[8] G. Velve-Casquillas, C. Fu, J. Cramer,S. Meance, A. Plecis, D. Baigl, J-J. Greffet, Y. Chen, M. Piel, P. T. Tran, “Fast microfluidic temperature control for high resolution live cell imaging”, Lab on a Chip, 2011

[9] F. Cantoni, G. Werr, L. Barbe, A. M. Porras, M. Tenje, A microfluidic chip carrier including temperature control and perfusion system for long-term cell imaging”, HarwareX, 2021

[10] F. Jiang, Y. Xu, J. Song, H. Lu, « Numerical Study on the Effect of Temperature on Droplet Formation inside the Microfluidic Chip”, Journal of Applied Fluid Mechanics, 2018

[11] B. Riechers, F. Wittbarcht, A. Hütten, T. Koop, “The homogeneous ice nucleation rate of water droplets produced in a microfluidic device and the role of temperature uncertainty” Physical Chemistry Chemical Physics, 2013

[12] D. Ross, L. E. Locascio, “Microfluidic Temperature Gradient Focusing”, Analytical Chemistry, 2002

[13] T. Matsui, J. Franzke, A. Manz, D. Janasek, “Temperature gradient focusing in a PDMS/glass hybrid microfluidic chip”, Electrophoresis, 2007

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