High-Recovery Submicron Particle Detection Enabled by Weakly Deformed Thread Flow

Currently, flow cytometry has achieved a 90% recovery rate for particles larger than 1 μm via sheath flow-assisted microfluidic technology. However, prevailing methodologies are inadequate in achieving high-recovery detection of submicrometer particles, primarily due to engineering challenges associated with the kinetic manipulation of these particles. In this paper, the weakly deformed thread flow state based on the weak diffusion regime is identified and studied to improve the recovery rate. The parameters that influence the flow state are ascertained and optimized by utilizing the finite element method (FEM), and a detailed weakly diffusive phase diagram is mapped. Concurrently, in experiments, a corresponding long depth-of-field (DOF) fluorescence microscopy system and the signal analysis methodology are developed, resulting in a 94.3% recovery rate for 1 μm particles and 85.1% for 0.5 μm particles. The findings may find potential applications in the quantitative detection of microorganisms, including Escherichia coli (E. coli) and mycoplasma, in natural water bodies.