On-Chip 3-D Imaging and Counting of Particles Transported in a Microfluidic Channel Based on Light-Field Microscopy

Rapid acquisition of 3-D volumetric information and accurate counting are significant in observing and monitoring specimens moving in microfluidic channels. This study introduces a novel approach of 3-D image flow cytmetry (IFC) using light-field microscopy that images the microfluidic channel with a microlens array (MLA) and reconstructs a complete 3-D volume from a single frame. To create the custom MLA, a cost-effective method is developed, combining gray-scale photolithography, nickel electroplating, and nanoimprinting. Furthermore, a calibration procedure is devised to rectify aberrations within the imaging system prior to 3-D reconstruction. The counting process employs an algorithm based on local intensity peak identification to quantify and locate particles moving in a microchannel, achieving counting accuracies around 95%. In comparison to existing 3-D IFCs, our method offers distinct advantages, including the capability for high throughput data capture and 3-D imaging fast moving samples without necessitating complex microchannel designs.