High-speed scattered-light imaging for sizing respiratory droplets

Roth, Adrian; Frantz, David; Stiti, Mehdi; Berrocal, Edouard

doi:10.1016/j.jaerosci.2023.106257

Cited by 2 publications

(3 citation statements)

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“…Indeed, our funnel-guided and direct injection measurements yield very similar profiles for these activities and agree fairly well with the prior literature [37,44]. However, this funnel-guided mode fails for larger speech droplets generated at the front of the oral cavity (lips and teeth) [45] that exit the mouth at speeds as high as 30 m/s [32], while having a mass that exceeds their dehydrated mass by up to two orders of magnitude [37]. With the lips less than ~7 cm from the funnel surface, the Stokes number for such droplets is greater than one, making them subject to impaction or "splatter".…”

Section: Discussionsupporting

confidence: 88%

“…Another study used both APS and light scattering video observations of the respiratory aerosol, finding particle counts consistent with prior APS measurements but also observing impressive clouds of particles that appeared to contain numerous aerosols much larger than observed by their APS [29]. However, precise measurements of the sizes and trajectories of ejected particles from high-speed video are limited by their often rather narrow field of view and remain restricted to technologically highly advanced laboratories [30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 67%

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Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

Kakeshpour,

Bax

2024

Atmosphere

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Modeling of airborne virus transmission and protection against it requires knowledge of the amount of biofluid emitted into the atmosphere and its viral load. Whereas viral concentrations in biofluids are readily measured by quantitative PCR, the total volume of fluids aerosolized during speaking, as measured by different researchers using various technologies, differs by several orders of magnitude. We compared collection methods in which the aerosols first enter into a low-humidity chamber either by direct injection or via commonly used funnel and tubing arrangements, followed by standard optical particle sizer measurement. This “collect first, measure later” approach sacrifices the recording of the temporal correlation between aerosol generation and sound types such as plosives and vowels. However, the direct-injection mode prevents inertia deposition associated with the funnel arrangements and reveals far more intermediate-size (5–20 μm in diameter) particles that can dominate the total mass of ejected respiratory aerosol. The larger aerosol mass observed with our method partially reconciles the large discrepancy between the SARS-CoV-2 infectious dose estimated from superspreader event analyses and that from human challenge data. Our results also impact measures to combat airborne virus transmission because they indicate that aerosols that settle faster than good room ventilation rates can dominate this process.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 67%

Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

Kakeshpour,

Bax

2024

Atmosphere

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“…Flow visualization [27] and droplet sizing measurements are generally carried out using Mie scattering measurement [28,29]. In this study, measurement of the nozzle was conducted using high-speed imaging and both unassisted nozzles, AN2 and AN3, were (A) Viability of sprayed donor keratinocytes via flow cytometry and trypan blue staining.…”

Section: High-speed Imagingmentioning

confidence: 99%

High-Speed Fluorescence Imaging Corroborates Biological Data on the Influence of Different Nozzle Types on Cell Spray Viability and Formation

Heuer,

Stiti,

Eras

et al. 2024

JFB

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Treating severe dermal disruptions often presents significant challenges. Recent advancements have explored biological cell sprays as a promising treatment, but their success hinges on efficient cell delivery and complete wound coverage. This requires a good spray distribution with a small droplet size, high particle number, and ample surface coverage. The type of nozzle used with the spray device can impact these parameters. To evaluate the influence of different nozzles on spray characteristics, we compared air-assisted and unassisted nozzles. The unassisted nozzle displayed small particle size, high particle number, good overall coverage, high cell viability, preserved cell metabolic activity, and low cytotoxicity. Air-assisted nozzles did not perform well regarding cell viability and metabolic activity. Flow visualization analysis comparing two different unassisted nozzles using high-speed imaging (100 kHz frame rate) revealed a tulip-shaped spray pattern, indicating optimal spray distribution. High-speed imaging showed differences between the unassisted nozzles. One unassisted nozzle displayed a bi-modal distribution of the droplet diameter while the other unassisted nozzle displayed a mono-modal distribution. These findings demonstrate the critical role of nozzle selection in successful cell delivery. A high-quality, certified nozzle manufactured for human application omits the need for an air-assisted nozzle and provides a simple system to use with similar or better performance characteristics than those of an air-assisted system.

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High-speed scattered-light imaging for sizing respiratory droplets

Cited by 2 publications

References 42 publications

Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

High-Speed Fluorescence Imaging Corroborates Biological Data on the Influence of Different Nozzle Types on Cell Spray Viability and Formation

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