AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Probing Aerosol Particle Interfaces with Biphasic Microfluidics
CARI DUTCHER, Andrew Metcalf, University of Minnesota, Twin Cities
Abstract Number: 198 Working Group: Aerosol Chemistry
Abstract Aerosol particles are complex microenvironments, which 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, such as ambient environmental conditions and the chemical composition of the respective phases, 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 novel 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 (e.g., (NH$_4)$_2SO$_4, NH$_4NO$_3) and dicarboxylic acids (e.g., malonic, glutaric, and maleic acid). From these measurements, important thermodynamic, kinetic, and rheological properties of the atmospheric aerosol mimics can be explored, yielding insight into multiphase aerosol particle dynamics.