Development of 3D-printed micro-lenses at the edge of waveguides of flow cytometry and optical coherence tomography photonic integrated circuits

Flow cytometry (FCM) contributes significantly to healthcare by enabling the rapid and accurate analysis of cell populations, which enhances our ability to diagnose, monitor, and assess treatment for conditions such as cancer and stroke. A multi-sensing biophotonic platform has been designed, integrating innovative FCM and Optical Coherence Tomography (OCT) photonic integrated circuits (PICs) and focusing on the detection of extracellular vesicles (EVs) down to 140 nm. The OCT module is utilized to ensure the validity of FCM measurements. The platform's micro-optic elements, designed for light manipulation within the sensing PICs, serve as interfaces between the photonic and fluidic components. Focusing lenses illuminate and collect light at specific flow channel points for FCM measurements at wavelengths of 520 and 638 nm, while the OCT module uses focusing micro-lenses for illumination and collection at 790 nm. This work presents the design, fabrication, and testing of the micro-lenses, achieving optical losses as low as 0.3 dB, equivalent to a coupling efficiency of up to 93%.