10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Toward the Development of a Portable Single-Particle Fluorescence Spectrometer for Inexpensive Analysis of Bioparticles Collected on a Substrate
BENJAMIN E. SWANSON, Donald R. Huffman, J. Alex Huffman, University of Denver, CO
Abstract Number: 1569 Working Group: Low-Cost and Portable Sensors
Abstract Bioaerosols, such as fungal spores, pollen, plant fragments, and bacteria, are present in all ecosystems and everywhere people live and work. They are linked to interesting environmental systems and are the cause of a variety of health effects, from seasonal allergies to airborne infections. In particular, allergenic effects caused by anemophilous (airborne) pollen torment huge fractions of the population and result in significant societal cost in terms of missed days of work and school. While daily weather forecasts now routinely include predictions of pollen levels, the direct measurements that support these predictions are most commonly accomplished through collection and optical microscopy performed by trained individuals. Much effort has been invested in the development of autonomous pollen counters over the last several decades, but these efforts have not yet produced small or inexpensive sensors capable of characterizing pollen with high reliability. In particular, many instruments utilized laser- or light-induced fluorescence (LIF) to interrogate particles. Real-time LIF instruments for bioaerosol detection are generally either costly to purchase (i.e. >$100k) or offer poor spectral resolution and poor discrimination ability.
Here we describe work toward the development of a handheld, portable instrument for the characterization of fluorescence spectra from many individual particles collected onto a substrate. The presentation will provide an overview of the properties of a benchtop version of instrument that was recently published [1]. The instrument utilizes four excitation sources (280 nm, 370 nm, 405 nm, and 450 nm) to probe a broad range of fluorophores and can collect fluorescence spectra from particles larger than approximately 0.5 µm in size. We showed the application of the first version of the instrument to four species of pollen [2], highlighting the ability to successfully separate pollen species using the K-means clustering algorithm.
We then applied the experience with the benchtop instrument to a prototype, handheld instrument (version 2) built using the same general principles. The smaller instrument (13 x 13 x 7.5 cm; 58 g) utilizes two excitation sources at a time and a Raspberry Pi camera as a detector, but collects the same information from each individual particle as version 1. Both instruments collect particle size and well-resolved fluorescence emission spectra (400 – 750 nm at ca. 2 nm resolution) for each excitation source. The small version was produced as a battery-powered aerosol detection system, as published [1]. Recent improvement in excitation sources used in the instrument have not yet been engineered to run on batteries, but this is planned. We will show an overview of the spectra collected by instrument version 2 and will demonstrate the ability of the instrument to differentiate between pollen species. The instrument is still in development, and at present an aerosol collection system is not yet coupled to the detection optics. Once a collection system is paired to the detector, we anticipate that a portable version of the spectrometer will represent a fundamental step forward in the ability to characterize pollen particles at a significantly lower cost than existing single-particle LIF spectrometers. We anticipate that it will also enable pollen or mold spore detection at higher spatial resolution than is currently available. The instrument was also designed as a tool for the investigation of particles and for education about fluorescence spectra by citizen scientists or schools.
References: [1] Huffman, D. R., Swanson, B. E., and Huffman, J. A.: A wavelength-dispersive instrument for characterizing fluorescence and scattering spectra of individual aerosol particles on a substrate, Atmos. Meas. Tech., 9, 3987-3998, 2016. [2] Swanson, B. E. and Huffman, J. A.: Development and characterization of an inexpensive single-particle fluorescence spectrometer for bioaerosol monitoring, Optics Express, In Press, 2018.