Capillary Aerosol Generator for Continuous Production of Controlled Aerosol

      Goedertier, D.; Lucci, F.; Radtke, F.; Vanscheeuwijck, P.; Hoeng, J.; Kuczaj, A.; Lee, T.; Tan, W.; Krishnan, S.

      Conference date
      Mar 15, 2021
      Conference name
      Society of Toxicology (SOT) Annual Meeting 2021

      The capillary aerosol generator (CAG) concept was developed nearly 20 years ago and has found various applications, including in generation of pharmaceutical aerosols. We have developed our own setup for compact generation, dilution, and delivery of aerosols generated from the CAG. The objective of these developments was to establish and characterize a system for continuous aerosol generation from liquid mixtures present in e-vapor products for rodent inhalation exposure. The physical process of aerosol generation from liquid mixtures in the CAG is complex and follows various stages with varying thermodynamic conditions. The liquid is supplied via a pump at a controlled flow rate to a capillary, which is continuously heated beyond the boiling point of the mixture, causing bursts of vapors to be generated and discharged from the capillary outlet at a temperature and pressure dictated by the thermodynamic conditions. Then, the supersaturated vapors are cooled down with an ambient cold air stream, triggering nucleation processes and subsequent condensation. For inhalation purposes, the generated aerosol is often diluted to control the delivered dose of constituents, further contributing to the complexity of the overall aerosol generation process. We tested our system in numerous configurations, including with 0.2-1.0 mL/min liquid mixture supply, 200-300°C capillary temperature, 10-100 L/min ambient cold streams for aerosol nucleation, and subsequent dilution of the aerosol with fresh filtered processed air to achieve the desired aerosol concentration for inhalation It was determined that, at a capillary temperature of 250°C and an ambient cold stream of 10 L/min, it was possible to achieve a particle size with a mass median aerodynamic diameter below 1.5 μm. The aerosol was further diluted to achieve the final target concentration of the aerosol constituents. With our experimental work, we have demonstrated that the CAG can be used for continuous aerosol generation with consistent particle size distribution and refined concentrations suitable for rodent inhalation studies. In addition, we performed a comparative study between diluted aerosols from an e-device and the CAG, where we reached equal particle size distributions and yields from the different compounds from the e-liquid.