Flow stokes microscopy for high throughput classification of marine particles

High throughput classification of marine particles facilitates the fast environment monitoring of harmful microalgae blooms and microplastic pollution. A conceptual setup of flow Stokes microscopy is based on a Stokes microscope whose imaging area is passed through by the suspension flow in a microchannel to measure a time series of Stokes images. The setup's measurement speed is 4.25 ml per hour and the particulate concentration error is less than 6 %. Standard microplastics and cultured microalgae are measured and classified with a general accuracy larger than 99 %. Also, some of them are accurately classified when mixing with the natural seawater. Both the imaging and polarization features' contributions are analyzed. Improvements in the microchannel are discussed to achieve higher throughput, more robust classification, and broader application. This work demonstrates the flow Stokes microscopy's power for high throughput classification of marine particles, which provides a promising tool in future aquatic environmental monitoring.