X-ray imaging for respiratory droplet deposition on face masks

Upon coughing or sneezing, the expelled respiratory droplets from an infected individual contain a virus load that inevitably contacts several surfaces, such as face masks, representing the main route of disease transmission. Since the early COVID-19 global outbreak, health organizations and governmental disease control task forces urged the population to use face masks as a prevention measure. Understanding the multilayered porous materials that constitute face masks and the dynamics between evaporation and absorption of respiratory droplets becomes crucial to assess the risk of disease transmission if not carefully handled. In the present study, virus-sized nanoparticles were suspended in artificial saliva. After the surrogate respiratory droplet evaporation on the face mask, the final deposit was observed using X-ray imaging. Consequently, X-ray imaging enabled a thorough analysis of facial masks' complex morphology. A physical model is proposed to explain the droplet evaporation, absorption, and the final viral deposit formation from the experimental data. The result can contribute to improve prevention measurements for respiratory diseases.