Project »MINSK«

In the MINSK project, Fraunhofer IPM has developed an innovative, miniaturized CO₂ sensor system. The aim was to continuously monitor the CO₂ concentration (tcpCO₂) in blood transcutaneously and maintenance-free over a longer period of time.

The key aspect here was the strong absorption of  the electromagnetic radiation of CO₂ at a wavelength of 4.3 µm. Through the photoacoustic effect, infrared active CO₂ gas molecules convert light energy into pressure variations. A microsensor with an optical path of only a few millimeters was developed for the required concentration range of 5% to 25% CO₂ with a resolution of 0.1%. The miniaturized photoacoustic sensor system was constructed by using a cost-effective MEMS microphone for acoustic recording, a MEMS infrared emitter and a hermetically sealed detection chamber. The interaction of the CO₂ with the infrared light takes place in the detection chamber, leading to a change in chamber pressure, which is read out via the microphone. This value is directly proportional to the gas concentration.

For this system, we have developed a gas-tight, flat-lying, dome-shaped housing with a diameter of approx. 18.5 mm which is attached to the skin via an adhesive patch. A heating element stabilizes the sensor at 42 °C to ensure localized hyperemia. The increased perfusion to the tissue enables CO₂ to diffuse through the skin and then through a gas-permeable membrane in the detection cell. Consequently, the TcPCO₂ value comes very close to the arterial value. The developed sensor, which is now available as a prototyp, connects via a thin cable to an evaluation device which also supplies the necessary energy.

Project financing

The MINSK project was financed as part of the Fraunhofer-Gesellschaft’s in-house Fraunhofer vs. Corona program.

Project duration

May 2020 to February 2021