Photoacoustic Detection of Nuclei Acid-Containing Water Droplets

It has been reported that the transmission route of SARS-CoV-2 is due to the transport and evolution of pathogen-containing aerosols and droplets. Detecting virus-laden aerosols and droplets could be valuable in reducing the pandemic of COVID-19. Coronaviruses have positive-sense single-stranded RNA (ssRNA) genomes. In this study, we explore the feasibility of photoacoustic (PA) detection of nucleic acid (NA) containing water droplets to model recent results acquired in our laboratory. A two-dimensional NA-containing water droplet model was implemented with randomly positioned water droplets. The diameter of water droplets was randomly distributed from 1 to 60 µm. The NA particles, simulating viral particles, were randomly positioned with the same number concentration (NC). Four different NCs were independently applied to investigate the effect of the NCs of NA particles on the PA signal generation. Monte-Carlo simulations were implemented using one million transmitted photons and a collimated laser beam (wavelengths from 100 to 370 nm). PA signals were computed based on Green's function approach, incorporating the directivity and the band limit of a single-element 300 kHz ultrasound transducer used in the experiments. The P A power was computed by using a root-mean-square. As a result, the total energy deposition increased with the NC of DNA at 260 nm, increasing the PA power. For 209 nm and 298 nm, on the other hand, the PA powers were the same regardless of the NCs of NA. This simulation study can provide insights into the PA sensing of viruses within aerosolized droplets.