Photoacoustic sensors (PAS) can detect gases in the concentration range of a few ppm with high sensitivity and selectivity. The photoacoustic effect, which generally describes the conversion of light energy into acoustic energy, was discovered by Alexander Graham Bell back in 1880 and can be detected using a microphone. These photoacoustic gas sensors are widely used in process control, the food industry and medicine. Advances in the production of micromechanical systems (MEMS) are enabling cost-effective manufacturing processes and further miniaturization of systems and components.
The focus of the completed PAS research project was the development of a piezoresistive microphone component based on MEMS for highly integrated photoacoustic gas sensors. Using a multi-layout approach, microphone chips with a very sensitive piezoresistive measuring bridge were developed. Some variants are suitable for wafer-level packaging. The realization of the 2 µm thick bending plate with the partially exposed edges was challenging. With the two-chamber system developed in-house, sensitivities of 0.26 µV/(ppm CO2), 0.006 µV/(ppm N2O), 0.005 µV/(ppm H2O) could be determined after amplification. The sensor is suitable for an operating range from -40⁰C to 140⁰C. Applications include climate and environmental protection to improve energy management, air quality testing or in medical technology as highly sensitive breathing gas sensors. Due to the wafer-based production and the desired miniaturization, there is further potential for the production of customer-specific sensor elements in higher quantities at attractive costs.
The research and development work described was funded by the Federal Ministry of Economic Affairs and Climate Action (BMWK) in the research project “Photoacoustic gas sensor with reference gas sensor” (PAS).
Funding code: MF200114
