Coalescence Sampling and Analysis of Aerosols using Aerosol Optical Tweezers

We present a first exploratory study to assess the use of aerosol optical tweezers as an instrument for sampling and detecting accumulation and coarse mode aerosol. A sub-picolitre aqueous aerosol droplet is captured in the optical trap and used as a sampling volume, accreting mass from a free flowing aerosol generated by a medical nebuliser or atomiser. Real-time measurements of the initial stability in size, refractive index and composition of the sampling droplet inferred from Raman spectroscopy confirm that these quantities can be measured with high accuracy and low noise. Typical standard deviations in size and refractive index of the sampling droplet over a period of 200 s are