AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Freezing of Aerosol Liquid Mimics in a Microfluidic Device
ANDREW METCALF, Christopher Hogan Jr., Cari Dutcher, University of Minnesota, Twin Cities
Abstract Number: 275 Working Group: Instrumentation and Methods
Abstract In situ observations of atmospheric aerosol particle morphology are difficult; thus, controlled laboratory studies to understand the underlying physics that determine particle morphology are necessary. Recently, microfluidic experiments have been used to assess the surface activity of aerosol chemical mimics and secondary organic aerosol collected on filters to measure interfacial tension and predict the presence of liquid-liquid phase separation at thermodynamic equilibrium. These measurements provide important constraints for thermodynamic models and yet more variety of measurements are necessary to translate laboratory studies to atmospheric conditions.
In this talk, a new microfluidic experiment platform capable of temperature control to at least -40 degrees C will be introduced. The microfluidic device includes an embedded platinum resistance temperature detector array which precisely measures temperature at 19 points along the fluid flow channel. The microfluidic device sits on a temperature control block which has 7 discrete temperature zones capable of causing a temperature gradient along the fluid flow. Initial experiments with this new platform include high-speed observations of water droplet freezing and liquid-liquid phase separations driven by temperature changes. Multiple temperature zones also allow hot-cold-hot hysteresis cycles to be observed in single droplets.