Analysis of Human Breath by Millimeter-Wave/Terahertz Spectroscopy

Abstract

Breath gas analysis is a promising tool for medical research and diagnosis. A particularly powerful technological approach is millimeter-wave/terahertz (mmW/THz) spectroscopy, because it is a very sensitive and highly selective technique. In addition, it offers the potential for compact and affordable sensing systems for wide use. In this work, we demonstrate the capability of a mmW/THz spectrometer for breath analysis. Samples from three volunteers and a sample from ambient air were analyzed with respect to 31 different molecular species. High-resolution absorption spectra were measured by scanning two absorption lines from each species. Out of the 31, a total of 21 species were detected. The results demonstrate the potential of mmW/THz spectroscopy for breath analysis.

A Review of the State of the Art in Non-Contact Sensing for COVID-19

“…Terahertz radiation is considered the first choice in radiation exploitation due to the non-harmful properties to living cells [ 107 ]. A terahertz spectroscopy is an example of a powerful tool in medical research and diagnosis used for analysis of human breath samples and it offers a low cost [ 108 ].…”

Industrial Applications of Terahertz Sensing: State of Play

“…Custom-designed electronic systems were used to detect alcohol [181] and several bio-marker gases [182] in breath with good sensitivity. Rothbart et al [183] employed a specially designed gas cell which the probe beam would traverse multiple times (11 passes) to extend the interaction length with the contained gas and thus increase the absorption signal. Measuring between 220–330 GHz, they were able to detect 21 gases (water, hydrogen cyanide, carbon monoxide, nitrogen oxide, formaldehyde, methanol, hydrogen sulfide, acetonitrile, methyl isocyanide, acetaldehyde, ethanol, vynil isocyanide, acrolein, acetone, carbonyl sulfide, dimethyl sulfide, isoprene, butyraldehyde, methyl nitrite, pyruvic acid, butyric acid) (Figure 24).…”

Terahertz Gas-Phase Spectroscopy Using a Sub-Wavelength Thick Ultrahigh-Q Microresonator

“…In particular, because of the abundance of strong fundamental absorption lines of a large variety of molecules in this frequency range [1][2][3][4][5][6][7][8][9]. However, current cutting edge THz gas-phase spectrometers still require cumbersome multi-pass gas cells to reach sufficient sensitivity for trace level gas detection [10][11][12][13]. In order to fully exploit the potential of THz gas-phase spectroscopy, novel sensors that are highly frequency selective and sensitive to changes in the surrounding medium are required.…”

“…As a proof of concept, we demonstrate as an exemplar the detection of less than 4 parts-per-million by volume (ppmv) of water vapour at ambient conditions. Novel sensing schemes for minute water vapour concentrations are in immediate interest, for example, for lithium-ion battery manufacturing, semiconductor fabrication and pharmaceutical industries [11]. However, we envision that the presented compact THz gas-phase spectrometer with the ultrahigh-Q THz disc microresonator will enable a myriad of possibilities in, for example, medical or industrial applications.…”