Development of Dual Aerodynamic Particle Sizers Method to Understand Aerosol Plume Dynamics  

Yiliang Lance Jiang¹, Dan Hardy¹, Mahmoud Ahmed¹, Gareth Hardwell,² Richard Friend² and Jonathan P. Reid¹

¹University of Bristol, School of Chemistry, Cantock’s Cl, Bristol, BS8 1TS, United Kingdom

²Chiesi Ltd., 1 Bath Road Industrial Estate, Bath Rd, Chippenham, SN14 0AB, United Kingdom

Summary

Hygroscopic growth can play a crucial role in determining the size of the therapeutic particle, and, hence, affect the deposition profile of that inhalable medication. Single-particle levitation studies, such as comparative kinetic electrodynamic balance, tells us the hygroscopicity of a particle. However, in a therapeutic setting, the dynamics of a plume of aerosol are often more relevant. Therefore, a dual aerodynamic particle sizer method has been developed to measure the plume generated from the same actuation at two different relative humidity. A connector and two spacers were 3d-printed to connect the inhaler and suppress transient fluctuations in particle counting, respectively. A Python programme has been developed to better visualize the data obtained from the two Aerodynamic Particle Sizer. OriginLab was used to estimate the size distribution of the plume. In this study, a low concentration of sodium chloride has been nebulized, with the study benefiting from an abundance of salt hygroscopicity literature already available. The aerosol thermodynamic model E-AIM can be used to model the hygroscopic growth against the water activity curve of well-characterized substances including sodium chloride, allowing us to compare our changes in plume size distribution. Preliminary measurements demonstrate that the plume in the drier relative humidity exhibits a smaller mean of size distribution compared to that of the more humid one. The experimental results agrees with the E-AIM results. Further improvement and refinement is required both to the dual APS set up and to the programme to extract more accurate size distribution.

Key Message

A dual Aerodynamic Particle Sizer-based method has been developed to measure the size distribution of the same plume of aerosol at two different relative humidities. A programme has been developed to visualize and compare particle size distributions of droplets containing NaCl at different relative humidities and times.