Abstract
Field-portable observation and analysis of particulate matter (PM) is required to enhance healthy lives. Various types of the PM measurement methods are in use; however, each of these methods has significant limitations in that real time measurement is impossible, the detection system is bulky, or the measurement accuracy is insufficient. In this work, we introduce an optical method to perform a fast and accurate PM analysis with a higher-contrast microscopic image enabled by a side-illuminated total internal reflection (TIR) technique to be implemented in a compact device. The superiority of the proposed method was quantitatively demonstrated by comparing the signal-to-noise ratio of the proposed side-illuminated TIR method with a traditional halogen lamp-based transmission microscope. With the proposed device, signal-to-noise ratios (SNRs) for microbeads (5~20 µm) and ultrafine dust particles (>5 µm) increased 4.5~17 and 4~10 dB, respectively, compared to the conventional transmission microscope. As a proof of concept, the proposed method was also applied to a low-cost commercial smartphone toy microscope enabling field-portable detection of PMs. We believe that the proposed side-illuminated TIR PM detection device holds significant advantages over other commonly used systems due to its sufficient detection capability along with simple and compact configuration as well as low cost.
Highlights
Ever increasing particulate matter (PM), released from factories, automobiles, and thermal power plants, affects human health in various ways when absorbed into the human body through the respiratory tract and skin [1]
We have developed a simple, compact, and low-cost system for detecting micro particles and PM
When compared to the conventional transmission illumination, advantages of the proposed method were that higher-contrast images could be acquired with the developed system, and micro particles could be detected better with higher signal-to-noise ratios (SNRs), i.e., 4.5~17 dB for microbeads (5~20 μm) and 4~10 dB for ultrafine dust particles (>5 μm)
Summary
Ever increasing particulate matter (PM), released from factories, automobiles, and thermal power plants, affects human health in various ways when absorbed into the human body through the respiratory tract and skin [1]. Long-term exposure to air pollution can cause diabetes or even cause heavy metals to be accumulated in the bones of the human body resulting in neurological or cardiovascular related diseases [2,3,4]. To scope with those exposures by informing PM level, several technologies have been developed and utilized. Βray absorption, light scattering, and tapered element oscillating microbalances (TEOM). While the mass concentration method, β-ray absorption method, and TEOM method can provide accurate results, they require bulky systems and, are not easy to make them portable.
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