Compact on-chip fluorescence microscope for dynamic imaging of cellular processes and biomimetic systems.

Real-time and High-throughput fluorescence imaging is essential for probing dynamic cellular behavior in biomimetic and tissue-on-chip systems. While fluorescence microscopy provides high sensitivity and subcellular resolution, the intrinsic heterogeneity of these engineered tissues requires imaging multiple regions to obtain representative biological information. Meeting this need typically demands mechanical scanning systems, which add both hardware and software complexity and substantially increase cost. Here, we developed a compact and low-cost on-chip fluorescence microscopy platform that integrates a two-dimensional microlens substrate directly onto a complementary metal-oxide-semiconductor sensor to achieve high resolution and signal-to-noise ratio (SNR). Excitation light is delivered laterally through a prism to induce total internal reflection, effectively rejecting background illumination and allowing only fluorescence emission to reach the detector. The system's optical geometry was optimized using analytical modeling and numerical simulations to maximize photon collection and SNR. Using this optimized system, we first demonstrated its capability at the cellular level by capturing drug-induced oxidative stress and rapid intracellular signaling dynamics in BT-20 breast cancer cells. Once we were successfully able to monitor these dynamic processes, we next applied the system to biomimetic models. In a microfluidic tumor-endothelial co-culture, we visualized the passage of small molecules, nanoparticles, and ions across the endothelial barrier under controlled flow conditions. Integration with microfluidic co-culture systems further demonstrated its ability to study complex interactions within tumor microenvironments. By combining simplicity, sensitivity, and compatibility with biomimetic platforms, this on-chip fluorescence microscope enables wide-field monitoring of cellular dynamics across large populations, allowing observation of cell-to-cell variability and supporting applications in drug screening, cellular signaling studies, and tissue-on-chip research.