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Realtime Digital Inline Holography for High Fidelity, in Situ and Non-intrusive Aerosol Measurements
JIARONG HONG, Ruichen He, Rafael Placucci, Lei Feng, University of Minnesota
Abstract Number: 638
Working Group: Instrumentation and Methods
Abstract
The analysis of particle concentration, size, and shape distribution is critical in many engineering applications and fundamental research, including spray coating, pollutant monitoring, cellular identification, and sorting, etc. Unlike conventional techniques, such as laser diffraction and phase Doppler analysis, the emerging digital inline holography (DIH) technique could provide imaging-based quantification of particle size and shape using a simple and inexpensive setup without knowledge of particle characteristics. Nevertheless, DIH is computationally expensive. In this presentation, we introduce a novel mobile DIH device for high-precision in situ non-intrusive characterizations of particles. Compared to conventional DIH, the proposed system leverages machine-learning, multi-threading programming, and embedded graphic processing units (GPUs) to achieve real-time hologram acquisition and processing. Here we present our recent works applying DIH techniques for aerosol measurements. Specifically, we will first demonstrate the application of DIH for measuring the respiratory droplets generated from normal breathing. The measurements reveal two distinct types of particles in the respiratory flow, i.e., round and faceted, with an average size of 1.7 µm and concentration varying significantly across different individuals. Particularly, the fraction of faceted particles changes from 26% to 40% across different participants and correlates with the peak of normalized exhaled flow rate. Moreover, the real-time DIH has also been used to quantify the aerosols generated from an ultrasonic scaling procedure used in dental operations and offers a robust assessment of the effectiveness of different preventive strategies (e.g., saliva ejector, high volume evacuator, and extraoral local extractor) on mitigating the spread of aerosols over a wide range of sizes. Additional applications including real-time indoor air monitoring will be presented. Overall, we show that real-time DIH can be widely employed in various aerosol diagnostics and environment monitoring involving particles over a broad range of size (from submicron to millimeter), morphology, and concentration.