10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Droplet Microfluidics Based Detector for Bioaerosols
BRIAN DAMIT, Johns Hopkins University Applied Physics Laboratory
Abstract Number: 929 Working Group: Bioaerosols
Abstract Robust monitoring technologies for airborne microbes are critical to mitigate the health effects posed by environmental and agricultural bioaerosols, and biowarfare attacks. Limitations of current detectors (e.g. slow response time and expensive consumption of reagents) have compelled the development of new technologies. In this work, a detector was developed which applies droplet microfluidics to bioaerosol detection. Droplet microfluidics, a subfield of microfluidics, is based on the creation of picoliter/nanoliter droplets containing compartmentalized reagents and supports enhanced assays and fluidic manipulations. The bioaerosol detector here functions by precisely focusing aerosols directly into these droplets, and thus harness the benefits offered by a droplet microfluidics platform.
A breadboard detector system was constructed which consisted of an aerodynamic focusing lens, aerosol-focusing nozzle, custom microfluidic droplet chip, and fluorescence microscope. Computational fluid dynamic simulations and Lagrangian particle tracking modeling identified the optimal settings for aerosol focusing into the droplets. Preliminary experiments, wherein test PSL aerosols were focused and deposited onto solid substrates, demonstrated sub 200-μm spot diameters for aerodynamic sizes of 2-5 μm. After obtaining fine aerosol focusing, collection of aerosols in the droplets was achieved by positioning the chip below the focusing nozzle, forming a pinned air-liquid interface at the chip surface, and then focusing test aerosols into that interface. Real-time inspection via microscopy confirmed aerosol capture at the interface. The measured recovery efficiency of aerosols from the droplets was aerosol-size dependent and ranged from about 27% to nearly 100%.
Finally, to prove bioaerosol collection and detection, a droplet propidium iodide (PI) assay was performed: the system distinguished between E. coli and non-biological aerosols within 20 s of PI incubation. Overall, this work established the technique of direct collection of aerosols into a convenient droplet microfluidic platform for the purpose of rapid bioaerosol detection.