Applying 8-foci imaging to instantaneous three-dimensional flow field reconstruction

Advances in microfluidics have enabled the exploration of complex fluid dynamics within intricate geometries, facilitating both the fabrication of sophisticated microchannels and the study of realistic three-dimensional (3D) flow environments. However, capturing 3D flow fields with high spatial and temporal resolution still remains a significant challenge due to the limitations of current experimental techniques. Here, we introduce a novel approach using widefield multifocus microscopy to achieve instantaneous 3D flow reconstruction by simultaneously imaging eight axial planes. This technique was applied to investigate particle dynamics in microchannels engineered to replicate vascular bifurcations. In cylindrical channels mimicking blood vessels, we observed radial particle migration toward the channel center, reminiscent of margination in blood flow. At bifurcation points, particle collisions and deceleration were localized at the apex, followed by redistribution into downstream branches. Our 3D imaging further revealed complex transport phenomena, including non-Gaussian lateral displacements, Lévy flight-like behavior, and net migration away from channel walls. These findings underscore the importance of true volumetric flow measurements for elucidating particle-wall interactions and the behavior of biological fluids in both physiological and engineered 3D microenvironments.