Flow Plastometry of Microplastics Using Optical Line Tweezers

Microplastics (MPs), both primary and secondary, have been reported to cause adverse effects on ecosystems, including human health. A substantial portion of MPs has been identified in aquatic environments such as oceans, rivers, lakes, reservoirs, and even drinking water systems. The potential human health risks of MPs absorbed through water intake have been increasingly reported. The chemical composition, which includes core components and surface coatings, as well as physical characteristics such as size and shape, collectively determines their toxicity. However, preparation steps such as density separation, digestion, and filtration can chemically modify microplastics and cause matrix interference, necessitating the development of advanced analytical methods. This study introduces a novel system employing Raman line monitoring and trapping system to achieve simultaneous morphological and chemical analysis of MPs in a flow channel. Furthermore, we developed a protocol for acquiring Raman signals from particles as small as 500 nm through precise optical immobilization. Our approach can provide a powerful tool for real-time monitoring and characterization of MPs in aquatic environments.