Waveguide-Based\nMicrowave Nitric Oxide Sensor for\nCOVID-19 Screening: Mass Transfer Modulation Effect on Hollow Confined\nWO<sub>3</sub> Structures

Serious\nacute respiratory syndrome coronavirus-2 (SARS-CoV-2)\nposes\na tremendous threat to global public health. Recently, the Food and\nDrug Administration approved the emergency use of volatile organic\ncomponents as detection biomarkers for COVID-19, ushering in a new\nera of portable, simple, and rapid epidemiological screening based\non breath diagnosis. Nitric oxide (NO) is an important biomarker indicating\nthe degree of inflammation in the respiratory tract. In this study,\na hollow multishelled structured WO<sub>3</sub> (HoMSs-WO<sub>3</sub>)-based waveguide microwave gas sensor (MGS) was fabricated to detect\ntrace levels of NO in exhaled breath for the preliminary diagnosis\nof COVID-19. The sensor showed excellent reusability and selectivity\nand efficiently detected NO in the 10–100 ppb, with a sensitivity\nof 39.27 dB/ppm and a detection limit of 2.52 ppb. In addition, a\nsound correlation was observed in the measurement results between\nthe MGS and the Sunvou detector for detecting NO from the exhaled\nbreath of clinical COVID-19 patients. The difference between the two\nmeasurements was within 1.96 standard bias, and the consistency range\nwas −12 to 17 ppb, thus fully demonstrating the significant\npotential of the sensor in COVID-19 screening.