iHWG-MOX: A hybrid breath analysis system via the combination of substrate-integrated hollow waveguide infrared spectroscopy with metal oxide gas sensors.

According to its materials and operating parameters, MOX sensors respond to target gases only by a change in sensor resistance with lack in selectivity. By use of IR spectroscopy, highly discriminatory information from samples at a molecular level can be obtained and the selectivity can be enhanced. A low-volume gas-cell was developed for a commercially available semiconducting metal oxide (MOX) methane gas sensor and coupled directly to a mid-infrared gas sensor based on substrate-integrated hollow waveguide (iHWG) technology combined with a Fourier transform infrared spectrometer. This study demonstrates a sensing process with combined orthogonal sensors for fast, time resolved and synergic detection of methane and carbon dioxide in gas samples.