Abstract View
Rapid Detection of Single Bioaerosol Particles Using Circular Intensity Differential Scattering (CIDS)
YONG-LE PAN, Aimable Kalume, Jessica Arnold, Chuji Wang, Joshua Santarpia, U.S. Army Research Laboratory
Abstract Number: 315
Working Group: Bioaerosols
Abstract
It is highly desirable to detect life-threatening bioaerosols from atmospheric aerosols, in situ, rapidly and continuously. Single particle diagnostic techniques can obtain signatures of individual particles, rapid time variations of species, and information of low concentration particles that are generally obscured by other dominant particles in collected samples/ensembles. Currently early-warning biosensors are based on fluorescence and elastic scattering from single aerosol particle with high-false-alarm rate, while particles are successively drawn through the interrogation volume of sensors. It was reported that DNA helical structures in biological molecules have non-zero circular intensity differential scattering (CIDS, normalized Mueller scattering-matrix element S14) than that from isotropic particles. However, CIDS measurements were only carried out on suspension samples with a polarization modulator and rotating detector due to its ultra-weak signals (10^-3-10^-6). Such complex laboratory instrumentation is not readily deployable as field biosensor.
Here, we report an advanced design for measuring CIDS from single aerosol particles without any moving parts and modulator. The scattering phase function was obtained using a reflector to project scattering light at different angles onto a 1-D/2-D detector instead of rotating the detector. The differential signals were measured from a particle interacting with two illuminating laser beams with left- and right-circular polarizations, which were produced by fixed optical components without any modulator. This innovative setup shortens the measurements from tens of minutes to tens of microseconds. Primary measurements showed that 3 micron diameter bioaerosol [DNA-tagged polystyrene latex (PSL) microsphere and aggregate of B. subtilis spores] have at least 3 times stronger CIDS signals than non-bioaerosol particles (PSL and tryptophan molecules). This gives great promise for developing new early-warning biosensor with a potential to lower false alarm rate.
Acknowledgements
Thank DTRA CB10745 support.