Dynamic imaging and characterization of volatile aerosols in e-cigarette emissions using deep learning-based holographic microscopy

• Published in: arXiv.org 2021-03
• Main Authors: Luo, Yi, Wu, Yichen, Li, Liqiao, Guo, Yuening, Ege Cetintas, Zhu, Yifang, Ozcan, Aydogan
• Format: Article
• Language: English
• Subjects: Additives; Aerosols; Algorithms; Cigarettes; Composition effects; Deep learning; Electronic devices; Holograms; Holography; Image reconstruction; Liquids; Machine learning; Measurement techniques; Microscopy; Nicotine; Particulate emissions; Propylene; Volatility
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2104.00525

Various volatile aerosols have been associated with adverse health effects; however, characterization of these aerosols is challenging due to their dynamic nature. Here we present a method that directly measures the volatility of particulate matter (PM) using computational microscopy and deep learning. This method was applied to aerosols generated by electronic cigarettes (e-cigs), which vaporize a liquid mixture (e-liquid) that mainly consists of propylene glycol (PG), vegetable glycerin (VG), nicotine, and flavoring compounds. E-cig generated aerosols were recorded by a field-portable computational microscope, using an impaction-based air sampler. A lensless digital holographic microscope inside this mobile device continuously records the inline holograms of the collected particles. A deep learning-based algorithm is used to automatically reconstruct the microscopic images of e-cig generated particles from their holograms, and rapidly quantify their volatility. To evaluate the effects of e-liquid composition on aerosol dynamics, we measured the volatility of the particles generated by flavorless, nicotine-free e-liquids with various PG/VG volumetric ratios, revealing a negative correlation between the particles' volatility and the volumetric ratio of VG in the e-liquid. For a given PG/VG composition, the addition of nicotine dominated the evaporation dynamics of the e-cig aerosol and the aforementioned negative correlation was no longer observed. We also revealed that flavoring additives in e-liquids significantly decrease the volatility of e-cig aerosol. The presented holographic volatility measurement technique and the associated mobile device might provide new insights on the volatility of e-cig generated particles and can be applied to characterize various volatile PM.