(124c) Dynamic Surface Tension and Phase Transitions of Sea Spray Droplets Using Microfluidics

Sea spray aerosols (SSA) are comprised of particles and droplets with chemically complex microphysical properties, with composition and phase that can evolve dramatically with changes in the ambient environmental conditions. The resultant composition and phase inform the particle’s optical properties, water uptake and partitioning, and activation to cloud condensation or ice nuclei. In this work, recent advancements using laboratory microscale flows will be highlighted for marine based droplet systems through NSF Center for Aerosol Impacts on Chemistry of the Environment (NSF CAICE) collaborations, towards improved understanding of the properties and phase of sea spray aerosols in our atmosphere. Microfluidics offers the advantage of rapid and monodisperse droplet generation with precise temperature control. Microscale tensiometry methods for determining equilibrium and dynamic surface tension will be presented for aqueous systems containing soluble surfactants. Discussion of surfactant transport with flowing bubbly systems, including diffusion and surface adsorption mechanisms, will be provided. Microfluidic methods for measuring droplet phase transitions, including liquid-liquid phase separation and ice nucleation (IN), will also be highlighted. Temperature and relative humidity dependence of the phase transitions for model chemical systems along with bulk and sea surface microlayer sea water samples obtained from a simulated waveflume experiment through NSF CAICE partnerships are studied in static and high-throughput droplet microfluidic platforms. Discussion of analysis methods and automated detection and classification of frozen droplets using machine learning will also be provided.