Single Aerosol Particle Selection and Capture Using Laser Scattering and Fluorescence

Abstract

A dual wavelength UV-LIF fluorescence system that uses 266 nm and 355 nm laser pulses to sequentially excite single aerosol particles has been shown to provide significant discrimination between biological and ambient as well as differentiation among classes of biological particles. This particle classification data can then be used to trigger an electrostatic capture mechanism to deposit individual potential bio-threats particles onto a stainless steel substrate and particles that are not classified as targets are discharged with the exiting airflow. Timing and velocity information for each on-the-fly particle are critical for setting an appropriate delay to capture the particles of interest. A novel CW laser beam technique has been developed to measure the velocity of each particle and initiate a timing sequence. The electrostatic capture mechanism then electrically charges identified particles and produces a time-delayed electric field to drive them into the stainless steel substrate. The resulting collected sample is highly enriched with target, or potential threat, particles in comparison to their percentage in the ambient air. This presentation will describe the unique optical interrogation and diagnostic techniques that have been developed to make this achievement possible, as well as provide the latest system performance results.