After iterative rounds of optimization and validation, Radboud University has managed to develop the first QCAP sensor prototype. All the functional subcomponents have been fully integrated into a transportable platform, and the system has been successfully delivered to the Flanders Center of Postharvest Technology (VCBT) for real-time trace gas sensing.
R&D seldom proceeds as straightforward as initially thought, and the footprints of the QCAP sensor are certainly no exception. Within the past two years, the QCAP researchers at Radboud University have re-designed the hardware/software architecture, leading to the realization of the first robust, compact, and sensitive QCAP sensor prototype.
This prototype features a bright and broadband mid-infrared supercontinuum light source provided by NKT Photonics. The researchers integrated a reference photodetector into the spectrometer to counterbalance the power drift of the light source, improving the long-term stability of the sensor. The complex gas handling system in the prototype is specially designed for applications in VCBT, where small (~10 L) and middle (300 L) sized storage containers are mostly utilized. A versatile water trap is also implemented, allowing the detection of multiple gas species with reduced water interference. Remarkably, preliminary laboratory-scale apple fermentation experiments show very promising results with high reproducibility, successfully achieving sub-ppm sensitivity for ethanol detection.
Concerning the 210 km journey from Radboud University to VCBT during one of the coldest days of the past winter, it came as no surprise that the sensor prototype fell into hibernation at -4 °C. Fortunately, the warm welcome atmosphere of the local researchers awakened it, and more excitingly, the first broadband ethanol absorption fingerprints appeared at the sunrise horizon after overnight darkness.
Measurements associated with the first trial for a real pear storage container show very promising results. Ethylene concentration of 45.3 ppm has been successfully detected by the QCAP sensor prototype, in excellent agreement with the expected concentration of 43.5 ppm validated by gas chromatography-mass spectrometry (GC-MS). Controlled experiments involving various other gas species are currently underway, and the feedbacks will be valuable for developing and improving the second sensor prototype for potato storage applications in Cranfield University.
The research will be presented in the Conference on Lasers & Eletro-Optics / Europe (CLEO Europe) upcoming June in Munich.