Repository logo
 

Fluorescence lifetime imaging of optically levitated aerosol: a technique to quantitatively map the viscosity of suspended aerosol particles

Published version
Peer-reviewed

Type

Article

Change log

Authors

Fitzgerald, C 
Hosny, NA 
Tong, H 
Seville, PC 
Gallimore, PJ 

Abstract

We describe a technique to measure the viscosity of stably levitated single micron-sized aerosol particles. Particle levitation allows the aerosol phase to be probed in the absence of potentially artefact-causing surfaces. To achieve this feat, we combined two laser based techniques: optical trapping for aerosol particle levitation, using a counter-propagating laser beam configuration, and fluorescent lifetime imaging microscopy (FLIM) of molecular rotors for the measurement of viscosity within the particle. Unlike other techniques used to measure aerosol particle viscosity, this allows for the non-destructive probing of viscosity of aerosol particles without interference from surfaces. The well-described viscosity of sucrose aerosol, under a range of relative humidity conditions, is used to validate the technique. Furthermore we investigate a pharmaceutically-relevant mixture of sodium chloride and salbutamol sulphate under humidities representative of in vivo drug inhalation. Finally, we provide a methodology for incorporating molecular rotors into already levitated particles, thereby making the FLIM/optical trapping technique applicable to real world aerosol systems, such as atmospheric aerosols and those generated by pharmaceutical inhalers.

Description

Keywords

0299 Other Physical Sciences, Generic Health Relevance

Journal Title

Physical Chemistry Chemical Physics

Conference Name

Journal ISSN

1463-9076
1463-9084

Volume Title

18

Publisher

Royal Society of Chemistry
Sponsorship
European Research Council (279405)
European Research Council (Grant ID: 279405), Science and Technology Facilities Council (Central Laser Facility, Grant ID: LSF1207), Engineering and Physical Sciences Research Council (Grant ID: EP/I003983/1), Natural Environmental Research Council (Grant ID: NE/J500070/1)