AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Temperature Dependent Phase Study of Aerosols Using Droplet Microfluidics
PRIYATANU ROY, Cari Dutcher, University of Minnesota
Abstract Number: 163 Working Group: Instrumentation and Methods
Abstract Atmospheric aerosols containing multiple organic and inorganic components experience a broad range of relative humidities and temperatures which govern their phase state. Many aerosol properties including particle morphology, hygroscopicity, surface tension, viscosity, optical cross section and equilibrium partitioning are influenced by their phase state. In situ observation of factors including relative humidity and temperature on single aerosol droplets are difficult, whereas laboratory measurements using droplet microfluidics are both simple and cost-effective. In this work, microfluidic devices are used to generate and study phase states of aqueous droplets containing sea spray aerosol samples and chemical mimics using both static trap and flow-through approaches at temperatures as low as -40°C. The static trap device dehydrates trapped droplets in a quasi-equilibrium method to study the effect of relative humidity and water loss on liquid-liquid phase separation and crystallization at different subcooled temperatures inside a temperature-controlled cell utilizing liquid nitrogen cooling and resistive heating. Preliminary results show low temperatures do affect the phase separation behavior depending on the composition and solute ratios of the droplet. The high-throughput flow-through device measures ice nucleation temperature of droplets using on-chip platinum resistive temperature sensors and sits on top of a temperature control block with seven discrete temperature zones using Peltier elements which use the liquid nitrogen cooled temperature-controlled cell as a heat sink. The measurements will be used to predict the cloud and ice formation activity of both land-based and sea spray aerosols.