Thermal conductivity

The identification of a liquid or a mixture is important in microfluidics for a variety of reasons:

  • The performance of a micropump is viscosity dependent.
  • The exact degree of mixing of two liquids should be controlled.
  • The whole process depends on the fluid currently used.

One possibility is to measure the thermal conductivity of the fluid and thus identify it.

The ability to switch between fluids fairly easily and still allow the system to function optimally opens up a wide variety of applications for the microfluidic system.

Watch the thermal conductivity video to see the full experiment. You can also find more details in the case study.

About the video

Since the identification of the fluid in a microfluidic system is so important, our partner Sensirion has been working on an in-line and in-situ solution:
A thermal conductivity sensor.

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This sensor measures the thermal conductivity of the fluid in the system. This allows you to identify the fluid and its viscosity. With this knowledge, you can then set the perfect frequency for the optimal flow rate.

This is an extremely efficient system since you don’t need a separate sample to measure the thermal conductivity, and you can also identify the mixing ratio of the fluid. Simply add this sensor to your system and you will have all the information you need in the software you use to control the system anyway.

About the Case Study

Diaphragm-based micropumps such as the mp6 micropump can be controlled by the frequency (how often per second the diaphragm is actuated) and the control voltage of the actuating elements (control of the diaphragm stroke). Both parameters must be adjusted to the viscosity of the fluid and the desired flow rate. Especially in applications where different fluids are pumped by the same pump, it is useful to automate this manual step.

To this end, this case study shows that our mp6 micropump, in conjunction with Sensirion’s SLF3C-1300F sensor, which measures thermal conductivity, can detect the fluid, creating the possibility to automate the pump parameter setting.