Multi-band millimeter wave / terahertz breath sensor based on molecular absorption spectroscopy

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Breath analysis has an enormous potential in clinical diagnosis. It is inherently safe and non-invasive. It can be used to detect diseases, monitor disease progression or monitor therapy. Despite of its potential breath analysis is still not widely used. One of the reasons is inadequate instrumentation, which is often expensive, difficult to use, and not portable. In addition most practical sensors can only detect one species and it is not possible to measure a characteristic pattern of many volatile organic compounds (VOCs) simultaneously with only one instrument. The common objective of the groups at Humboldt-Universität zu Berlin, Leibniz-Institut für Innovative Mikroelektronik, and Universität Marburg is to develop a novel, very sensitive and highly specific sensor for human breath analysis. The detection principle of the sensor is molecular absorption spectroscopy at millimeter wave (mmW) and terahertz (THz) frequencies. The sensor will allow detecting many relevant VOCs in human breath simultaneously. It consists of a frequency tunable mmW/THz transmitter (TX) and a receiver (RX). In a prior project the feasibility of such a mmW breath sensor has been demonstrated at frequencies around 240 GHz and breath gases have been measured. In this project the sensitivity, specificity and selectivity of the sensor will be significantly improved. This will be achieved by increasing the output power, sensitivity and linearity of the TX and RX. The frequency coverage of the sensor will be extended by two frequency bands centered at 480 GHz and 720 GHz, which allows more gases to be detected with higher sensitivity. Also a novel multi-band spectroscopy approach using the harmonics of the TX will be explored. A new absorption and gas handling system will reduce system losses and increase sensitivity. Since there is a lack of spectroscopic data of VOCs at mmW/THz frequencies a number of VOCs will be spectroscopically investigated using a dedicated laboratory spectrometer. The new developments will be integrated into a portable mmW/THz breath sensor. This sensor will be evaluated at Universität Marburg by applying the mmW/THz breath sensor to patients with lung diseases. Finally, the feasibility of a mmW/THz breath sensor for practical use in clinics and ambulances will be assessed. This interdisciplinary collaboration will contribute significantly to the implementation of breath analysis for routine medical diagnostics.