Microfluidics-Based Capture and Transfer of Single Aerosol Particle-Droplets for Surface Enhanced Raman Spectroscopy Analysis

WENDY FLORES-BRITO, Thomas Brubaker, Ryan Sullivan, Carnegie Mellon University

     Abstract Number: 507
     Working Group: Instrumentation and Methods

Abstract
Physicochemical analysis of individual aerosol particles continues to be a challenge since few techniques exist that can preserve an aerosol's individual identity while transferring the particle for subsequent chemical analysis. Here, we present initial results from combining our microfluidics-based aerosol droplet capture method with surface enhanced Raman spectroscopy (SERS) for online chemical analysis. The droplet capture method features direct activation of aerosol particles into droplets by water vapor condensation followed by droplet capture into an open channel microfluidic device while potentially maintaining their individual particle–droplet pair identity in an immiscible fluid. We compare the use of a Sequential Spot Sampler or Cloud Condensation Nuclei Counter as our droplet activation columns by collecting the fluorescein salt containing single-particle-droplets into the oil-filled open channel of the microfluidic device. The droplet capture efficiency was evaluated as a function of microdroplet size using fluorescence microscopy. Additionally, we present our microfluidic device design for incorporating SERS nanoparticles with the captured and transferred particle-droplet pairs; along with initial SERS test results.The combination of these methods will create a promising technique for the sampling and chemical analysis of single aerosol particles using small microfluidic devices.