Development and applications of light field microscopy systems for on-chip 3D characterization of dynamic samples in microfluidic platforms

Light field microscopy (LFM) has emerged as an instantaneous volumetric imaging method. This dissertation focuses on the development of LFM and its integration with microfluidic platforms to advance 3D imaging techniques for on-chip dynamic microscale samples. Firstly, a conventional LFM system based on a microlens array (MLA) is constructed. This section of the work outlines both the system setup and the accompanying 3D reconstruction algorithms. An innovation is a high-precision, cost-effective method for fabricating the MLA, which combines gray-scale photolithography with nanoimprinting. Additionally, a calibration method is introduced to correct for system aberrations. With this LFM system, a 3D image flow cytometry (IFC) system is developed on a continuous-flow microfluidics (CFM) platform. This setup efficiently achieves 3D imaging and counting of moving particles, demonstrating a 95% accuracy rate for 5 μm microbeads. Secondly, as LFM's spatial resolution and reconstruction artifacts remain challenges that hinder its broader application to 3D imaging in microfluidics, an improved LFM system is introduced that utilizes a staggered bifocal MLA. Compared to the conventional design, this enhanced system offers higher spatial resolution achieving a best lateral resolution of approximately 1.83 μm and an axial resolution of about 6.80 μm, while significantly reducing reconstruction artifacts. The performance of this improved LFM system is validated through 3D imaging of moving live cells suspended in droplets. Finally, the dissertation presents an integrated system that combines the improved bifocal MLA-based LFM with a digital droplet microfluidics (DMF) platform. This integrated approach includes the fabrication of a DMF device along with carefully optical and mechanical alignment with the LFM system. It allows for digital manipulation of droplets within a chip area of 70 × 50 mm². The resulting platform is capable of on-chip 3D imaging and tracking of both particles and cells in a volume exceeding 500 × 500 × 300 μm³ with a temporal resolution of 100 ms, and it also supports 3D monitoring of rapid cell lysis over several minutes. This successful integration demonstrates the synergistic benefits of LFM and DMF, offering digital control over droplets combined with 3D detection of fast-moving samples in microfluidic chips.