AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Microfluidic Measurements of Atmospheric Aerosol Mimic Rheology
ANDREW METCALF, Cari Dutcher, University of Minnesota, Twin Cities
Abstract Number: 197 Working Group: Aerosol Chemistry
Abstract The phase state and viscosity of atmospheric aerosol particles is of great interest due to physicochemical interactions that could influence gas-particle partitioning, chemical reactions, and water accommodation. Although aerosols have traditionally been treated as well-mixed, liquid spheres in modeling studies, recent experimental evidence suggests that ambient particles, particularly aged secondary organic aerosol (SOA), can be phase-separated into multiple liquid phases and/or in a highly viscous, glassy state. The mixing state and chemical composition of the aerosol and ambient conditions necessary to produce a distinct glassy state are an active area of current study and more information about the rheology of aerosol constituents will aid in our understanding of the occurrence of this phenomenon.
In this talk, our microfluidic platform will be used to probe rheological properties, such as viscosity, of atmospheric aerosol chemical mimics. Previously, the microfluidic platform in our group has utilized high-speed imaging to monitor interfacial phenomena at the microscale in order to derive interfacial tension between immiscible phases. Additional functionality on the microfluidic device works in conjunction with existing capabilities to probe additional rheological properties, such as viscosity, that provide a more complete description of the rheology of atmospheric aerosol constituents. The chemical mimics studied here include solutions of sucrose and dicarboxylic acids, commonly used as SOA surrogates, as well as pinene-derived SOA compounds found in biogenic aerosol. These systems will be compared to our previous work on a reacting, aqueous methylglyoxal—ammonium sulfate system. From these observations of the rheological properties of aerosol chemical mimics, the behavior of atmospheric aerosols due to interactions of liquid-liquid phase-separated interfaces within aerosol particles and possible transitions to a glassy state will be inferred.