Manipulation and 3D characterization of particles and cells through integrated light field microscopy and droplet...

Droplet microfluidics (DMF) generates, manipulates and processes discrete sub-microlitre droplets, which allows for precise control and high efficiency in conducting biological assays. On-chip 3D characterization of droplets and samples moving within them is challenging. Light field microscopy (LFM) based on a microlens array (MLA) has emerged as an instantaneous volumetric imaging method, with application to DMF where it can rapidly capture 3D information. However, the trade-off between spatial resolution and depth of field and challenges with reconstruction artifacts have so far limited LFM applications in microfluidics. In this work, a novel integrated system is introduced that combines a DMF device and a bifocal MLA-based LFM system. The system enables precise droplet manipulation alongside on-chip 3D imaging and tracking of particles and live cells in a volume exceeding 500 × 500 × 300 μm³ with a temporal resolution of 100 ms. The LFM has higher spatial resolution and less reconstruction artifacts compared to LFM systems based on conventional MLAs. Experiments applying microbeads and SW480 cells validate the system's capability for effective on-chip sample manipulation and 3D characterization with a best lateral resolution of approximately 1.83 μm and an axial resolution of about 6.8 μm. Additionally, the system successfully demonstrates manipulating rapid on-chip cell lysis and 3D monitoring with a temporal resolution of 300 ms over several minutes, highlighting the synergistic benefits of combining LFM with DMF.