High time resolution measurements of droplet evaporation kinetics and particle crystallisation

Hardy, Dan; Archer, Justice; Lemaître, Pascal; Vehring, Reinhard; Reid, Jonathan P.; Walker, Jim S.

doi:10.1039/d1cp02840e

Cited by 27 publications

(29 citation statements)

References 44 publications

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“…Interestingly, the salt crystals formed are smaller and more numerous as the RH is lowered ( SI Appendix , Fig. S6 ), consistent with previous work that has shown that there is a greater propensity for nucleation when droplets are dried at higher rates leading to more nucleation events and smaller final crystals forming a larger composite particle ( 61 ).…”

Section: Resultssupporting

confidence: 90%

The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment

Oswin

Haddrell

Otero-Fernandez

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the factors that influence the airborne survival of viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in aerosols is important for identifying routes of transmission and the value of various mitigation strategies for preventing transmission. We present measurements of the stability of SARS-CoV-2 in aerosol droplets (∼5 to 10 µm equilibrated radius) over timescales spanning 5 s to 20 min using an instrument to probe survival in a small population of droplets (typically 5 to 10) containing ∼1 virus/droplet. Measurements of airborne infectivity change are coupled with a detailed physicochemical analysis of the airborne droplets containing the virus. A decrease in infectivity to ∼10% of the starting value was observable for SARS-CoV-2 over 20 min, with a large proportion of the loss occurring within the first 5 min after aerosolization. The initial rate of infectivity loss was found to correlate with physical transformation of the equilibrating droplet; salts within the droplets crystallize at relative humidities (RHs) below 50%, leading to a near-instant loss of infectivity in 50 to 60% of the virus. However, at 90% RH, the droplet remains homogenous and aqueous, and the viral stability is sustained for the first 2 min, beyond which it decays to only 10% remaining infectious after 10 min. The loss of infectivity at high RH is consistent with an elevation in the pH of the droplets, caused by volatilization of CO 2 from bicarbonate buffer within the droplet. Four different variants of SARS-CoV-2 were compared and found to have a similar degree of airborne stability at both high and low RH.

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Section: Resultssupporting

confidence: 90%

The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment

Oswin

Haddrell

Otero-Fernandez

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

125

142

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“…The particles exhibit the same trends shown by Hardy et al, with fast-drying droplets resulting in crusts comprising higher numbers (∼10) of smaller (≤5 μm diameter) crystals and particles formed from slower drying made of a smaller number of crystals which are larger. 26 In the case of droplets drying close to the efflorescence RH (35 and 40% RH), droplets produce a single large (∼15 μm diameter) crystal. Between these extremes in RH a more diverse range of morphologies is observed, which may be due to the stochastic nature of particle nucleation and the window of crystallization that broadens with decreased evaporation rate.…”

Section: Resultsmentioning

confidence: 99%

“…The FDC has been introduced in detail previously, so here we just outline the main components. 26 Individual droplets are generated at a regular frequency (10s of Hz) using a DoD dispenser. The droplets propagate down through a vertical column in line with a gas flow of controlled flow rate and RH, as indicated in Figure 3 .…”

Section: Experimental Methodsmentioning

confidence: 99%

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Accurate Measurements and Simulations of the Evaporation and Trajectories of Individual Solution Droplets

et al. 2023

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A refined numerical model for the evaporation and transport of droplets of binary solutions is introduced. Benchmarking is performed against other models found in the literature and experimental measurements of both electrodynamically trapped and freefalling droplets. The model presented represents the microphysical behavior of solutions droplets in the continuum and transition regimes, accounting for the unique hygroscopic behavior of different solutions, including the Fuchs–Sutugin and Cunningham slip correction factors, and accounting for the Kelvin effect. Simulations of pure water evaporation are experimentally validated for temperatures between 290 K and 298 K and between relative humidity values of approximately 0% and 85%. Measurements and simulations of the spatial trajectories and evaporative behavior of aqueous sodium chloride droplets are compared for relative humidity values between 0 and 40%. Simulations are shown to represent experimental data within experimental uncertainty in initial conditions. Calculations of a time-dependent Péclet number, including the temperature dependence of solute diffusion, are related to morphologies of sodium chloride particles dried at different rates. For sodium chloride solutions, dried particles are composed of collections of reproducibly shaped crystals, with higher evaporation rates resulting in higher numbers of crystals, which are smaller.

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“…However, the typical time scale of droplet-to-particle conversion in high-temperature flames can be extremely short (usually on the order microseconds), making it difficult to investigate the evaporation process merely based on experimental instruments. 8,13 Besides, in an FSP experiment, it is challenging to isolate the droplet evaporation process for examination, as the solvent evaporation may be coupled with other processes during the droplet-to-particle conversion, such as collisions of the droplets, thermal decomposition of the solute, particle inception, etc. In this regard, as a complement to current experimental techniques, the molecular dynamics (MD) simulation method presents to be a powerful tool to provide atomic insights into the droplet evaporation process in the context of FSP synthesized NCM materials.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics study on evaporation of metal nitrate-containing nanodroplets in flame spray pyrolysis

et al. 2023

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High time resolution measurements of droplet evaporation kinetics and particle crystallisation

Abstract: A refined technique for observing the complete evaporation behaviour of free-falling droplets, from droplet generation to complete solvent evaporation, with ultra-high time resolution is introduced and benchmarked. High-resolution phase-delay stroboscopic...

Cited by 27 publications

References 44 publications

The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment

The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment

Accurate Measurements and Simulations of the Evaporation and Trajectories of Individual Solution Droplets

Molecular dynamics study on evaporation of metal nitrate-containing nanodroplets in flame spray pyrolysis

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