Mobile emission-based microspectrometer for the analysis of unknown gaseous substances

• Applicants: Dr.-Ing. Alexander Weiß; Dr.-Ing. Sven Zimmermann
• Subject Area: Microsystems ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 496343159

The planned project addresses the investigation of a novel, highly miniaturized and mobile spectrometer for unknown gases and gas mixtures. In contrast to the previously known concepts for gas spectrometers, which mainly use the absorption interaction between different gas components and light in the infrared range, the principle to be investigated in the project is based on the ionization of the unknown gas mixture in a plasma with simultaneous spectroscopic evaluation of the plasma emission. Since low-pressure plasmas are not suitable for mobile devices due to the inability to miniaturize pump systems for vacuum generation, the proposed project relies on the use of a microplasma source for the atmospheric pressure range, which will take the form of a compact split-ring resonator (SRR). Such plasma sources operate with microwave excitation, whereby large excitation powers are often required for ignition and operation of a stable discharge, which seriously complicates their use in mobile devices. The planned project will therefore focus very intensively on reducing the energy requirements of the plasma source, which will be achieved by, among other things, using higher excitation frequencies, utilizing higher-order resonance frequencies of the SRR, and an integrated ignition support. The operation under atmospheric pressure and the small geometrical dimensions hamper the rapid introduction of the gas to be analyzed into the plasma source. Therefore, the proposed project will work on an improved micropump that uses fluidic channels directly integrated into a moving structure. Since these pumps can only pump very small amounts of gas, new approaches to their characterization will also be investigated. Finally, the light emission of the plasma source has to be spectrally split and measured. To this end, the proposed project will explore a new MEMS-based microspectrometer for the VIS range that operates fully in-plane and can be tuned using electrostatic actuators. In addition, a suitable thin film detector will be designed and combined with the spectrometer. The MEMS spectrometer itself is already a novelty, its combination with a microplasma source to a lab-on-chip for spectral gas analysis has not been investigated yet.At the end of the project, a functional demonstrator is to be realized, which will be operated with a mobile energy source and built entirely in silicon technology. This demonstrator will finally allow the investigation of fluid dynamic, plasma physical and spectral optical effects as well as their interaction, which finally determines the dynamics, bandwidth, resolution and reproducibility of the gas spectrometer.

• DFG Programme: Research Grants