A new hot-stage microscopy technique for measuring temperature-dependent viscosities of aerosol particles and its application to farnesene secondary organic aerosol

Abstract. The viscosity of secondary organic aerosol (SOA) is needed to improve predictions air quality, climate, and atmospheric chemistry. Many techniques have been developed measure the micrometer-sized materials at room temperature; however, few are able as a function temperature for these small sample sizes. SOA in troposphere experience wide range temperatures, so measurement needed. To address this need, new method was based on hot-stage microscopy combined with fluid dynamics simulations. current can be used determine viscosities roughly 104 108 Pa s temperatures greater than temperature. Higher may measured if experiments carried out over multiple days. validate our technique, 1,3,5-tris(1-naphthyl)benzene phenolphthalein dimethyl ether were compared values reported literature. Good agreement found between measurements literature data. As an application SOA, lab-generated farnesene material measured, giving ranging from 3.1×106 51 ∘C 2.6×104 67 ∘C. We fit temperature-dependent data Vogel–Fulcher–Tammann (VFT) equation obtained fragility parameter 7.29±0.03, which very similar 7 α-pinene by Petters Kasparoglu (2020). These results demonstrate that using method.