Stability of respiratory-like droplets under evaporation

Seyfert, Carola; Rodríguez-Rodríguez, Javier; Lohse, Detlef; Marin, Alvaro

doi:10.1103/physrevfluids.7.023603

Cited by 20 publications

(29 citation statements)

References 38 publications

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“…We could see crystal formation within the small droplets as the concentration reaches the saturation concentration (Supporting Information Figure S3). Beyond the saturation concentration, it is reported that the evaporation rate decreases particularly at high humidity due to the hygroscopic effects of the salt . Similar effects may occur in our droplets as well, contributing to further slowing down of evaporation.…”

Section: Resultssupporting

confidence: 74%

“…Therefore, it is desirable to have systems that mimic the aerosol droplets as closely as possible. Because the consequences of evaporative volume change are the same regardless of the initial droplet size, large droplets are proposed as systems to mimic the evaporation of aerosols and microdroplets. − Although these large droplets can mimic the increasing concentration of chemicals by evaporation, smaller initial volumes may offer a better similarity to aerosols.…”

Section: Introductionmentioning

confidence: 99%

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Microfluidic Droplet Cluster with Distributed Evaporation Rates as a Model for Bioaerosols

et al. 2022

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Aerosols and microdroplets are known to act as carriers for pathogens or vessels for chemical reactions. The natural occurrence of evaporation of these droplets has implications for the viability of pathogens or chemical processes. For example, it is important to understand how pathogens survive extreme physiochemical conditions such as confinement and osmotic stress induced by evaporation of aerosol droplets. Previously, larger evaporating droplets were proposed as model systems as the processes in the tiny aerosol droplets are difficult to image. In this context, we propose the concept of evaporation of capillary-clustered aqueous microdroplets dispersed in a thin oil layer. The configuration produces spatially segregated evaporation rates. It allows comparing the consequences of evaporation and its rate for processes occurring in droplets. As a proof of concept, we study the consequences of evaporation and its rate using Escherichia coli (E. coli) and Bacillus subtilis as model organisms. Our experiments indicate that the rate of evaporation of microdroplets is an important parameter in deciding the viability of contained microorganisms. With slow evaporation, E. coli could mitigate the osmotic stress by K + ion uptake. Our method may also be applicable to other evaporating droplet systems, for example, microdroplet chemistry to understand the implications of evaporation rates.

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Section: Resultssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Microfluidic Droplet Cluster with Distributed Evaporation Rates as a Model for Bioaerosols

et al. 2022

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“…(iii) Evaporation does not affect the results much. Crucial in this lack of incidence is the fact that, because of their finite fraction c of non-water content, droplets do not fully evaporate, but shrink into residues (also called droplet nuclei), of final size of the order of c 1 3 times their initial size [28,66].…”

Section: Robustness To Simulation Details Related To the Flow Dynamicsmentioning

confidence: 99%

“…Next, the evaporation of droplets during their propagation was also introduced in the model. For that purpose, droplets were considered to be composed of pure water, until they shrunk to a diameter of one third of the original diameter, at which point evaporation was halted, to reflect the presence of a non-water content in the droplet [28,66]. The model for evaporation follows the approach developed by Spalding [83], similar to the one described by Bale et al [14].…”

Section: Alternative Physical Modelingmentioning

confidence: 99%

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From microscopic droplets to macroscopic crowds: Crossing the scales in models of short-range respiratory disease transmission, with application to COVID-19

Mendez,

Garcia,

Nicolas

2022

Preprint

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Short-range exposure to airborne virus-laden respiratory droplets is now acknowledged as an effective transmission route of respiratory diseases, as exemplified by COVID-19. In order to assess the risks associated with this pathway in daily-life settings involving tens to hundreds of individuals, the chasm needs to be bridged between fluid dynamical simulations of droplet propagation and population-scale epidemiological models. We achieve this by coarse-graining microscopic droplet trajectories (simulated in various ambient flows) into spatio-temporal maps of viral concentration around the emitter and coupling these maps to field-data about pedestrian crowds in different scenarios (streets, train stations, markets, queues, and street cafés). At the scale of an individual pedestrian, our results highlight the paramount importance of the velocity of the ambient air flow relative to the emitter's motion. This aerodynamic effect, which disperses infectious aerosols and thus mitigates short-range transmission risks, prevails over all other environmental variables. At the crowd's scale, the method yields a ranking of the scenarios by the risks of new infections that they present, dominated by the street cafés and then the outdoor market. While the effect of light winds on the qualitative ranking is fairly marginal, even the most modest ambient air flows dramatically lower the quantitative rates of new infections. The proposed framework was here applied with SARS-CoV-2 in mind, but its generalization to other airborne pathogens and to other (real or hypothetical) crowd arrangements is straightforward.

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From Microscopic Droplets to Macroscopic Crowds: Crossing the Scales in Models of Short‐Range Respiratory Disease Transmission, with Application to COVID‐19

2023

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Short‐range exposure to airborne virus‐laden respiratory droplets is an effective transmission route of respiratory diseases, as exemplified by Coronavirus Disease 2019 (COVID‐19). In order to assess the risks associated with this pathway in daily‐life settings involving tens to hundreds of individuals, the chasm needs to be bridged between fluid dynamical simulations and population‐scale epidemiological models. This is achieved by simulating droplet trajectories at the microscale in numerous ambient flows, coarse‐graining their results into spatio‐temporal maps of viral concentration around the emitter, and coupling these maps to field‐data about pedestrian crowds in different scenarios (streets, train stations, markets, queues, and street cafés). At the individual scale, the results highlight the paramount importance of the velocity of the ambient air flow relative to the emitter's motion. This aerodynamic effect, which disperses infectious aerosols, prevails over all other environmental variables. At the crowd's scale, the method yields a ranking of the scenarios by the risks of new infections, dominated by the street cafés and then the outdoor market. While the effect of light winds on the qualitative ranking is fairly marginal, even the most modest air flows dramatically lower the quantitative rates of new infections.

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Stability of respiratory-like droplets under evaporation

Cited by 20 publications

References 38 publications

Microfluidic Droplet Cluster with Distributed Evaporation Rates as a Model for Bioaerosols

Microfluidic Droplet Cluster with Distributed Evaporation Rates as a Model for Bioaerosols

From microscopic droplets to macroscopic crowds: Crossing the scales in models of short-range respiratory disease transmission, with application to COVID-19

From Microscopic Droplets to Macroscopic Crowds: Crossing the Scales in Models of Short‐Range Respiratory Disease Transmission, with Application to COVID‐19

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