Paper Number
CC2 

Session
Confined and Coupled Systems

Title
Probing aerosol particle interfaces with biphasic microfluidics

Presentation Date and Time
October 7, 2014 (Tuesday) 10:25

Track / Room
Track 6 / Washington C

Authors (Click on name to view author profile)

1. Dutcher, Cari S. (University of Minnesota, Mechanical Engineering)
2. Metcalf, Andrew R. (University of Minnesota, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Cari S. Dutcher and Andrew R. Metcalf
Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455

Speaker / Presenter 
Dutcher, Cari S.

Text of Abstract
Atmospheric aerosols are one of the major contributing factors to our climate, yet are the largest source of uncertainty in climate modeling. This uncertainty arises from the intricate nature of aerosol particles. As complex microenvironments, these particles can contain multiple interfaces due to internal liquid – liquid phase partitioning and the external vapor – liquid surface. These aerosol interfaces have profound effects on particle morphology, species uptake, equilibrium partitioning, activation to cloud condensation or ice nuclei, and optical properties. Many factors play a role in determining a particle’s internal structure, resulting in many possible particle configurations. For example, the aqueous and organic phases in a single aerosol particle may align in a side-by-side nodule morphology, whereas in other cases, the organic phase may form a film that can completely surround the aqueous phase. In order to fully predict a particle’s internal structure at a given temperature, relative humidity, and chemical composition, fundamental studies of interfaces observed in atmospheric aerosol particles are essential. In this talk, a method using biphasic microscale flows will be introduced for generating, trapping, and perturbing complex interfaces at atmospherically relevant conditions. These microfluidic experiments are conducted using phase contrast and fluorescence microscopy on a temperature-controlled inverted microscope stage with high-speed imaging to monitor interfacial phenomena at the microscale. Chemical compositions of the aqueous and organic phases studied here include electrolyte and water soluble organic acid species often observed in the atmosphere, such as mixtures containing ammonium salts and dicarboxylic acids. From these measurements and others, important rheological, thermodynamic, and kinetic properties of the atmospheric aerosol mimics can be explored, yielding insight into multiphase aerosol particle dynamics.