An enhanced print-pause-print strategy for modular stereolithography microfluidics with embedded optical access and functional integration

Stereolithography (SLA) enables the rapid fabrication of rigid microfluidic devices with complex geometries, but the integration of optical and functional components remains challenging. In particular, the incorporation of glass elements often leads to interfacial defects, incomplete polymerization, and reduced mechanical robustness. In this work, we present an enhanced print-pause-print (PPP) workflow for the fabrication of modular SLA microfluidic devices incorporating glass optical interfaces and functional modules. The proposed approach combines the insertion of a glass coverslip during fabrication with an intermediate curing step designed to polymerize residual resin trapped at the glass-resin interface. This additional processing step improves interfacial bonding and enables the fabrication of leak-free devices capable of withstanding pressures up to 3 bar without interfacial failure. The resulting architecture combines the optical quality of glass with the structural rigidity of SLA printing while preserving compatibility with post-fabrication insertion of functional modules. Hydrodynamic characterization demonstrates stable laminar co-flow behavior and good agreement with numerical simulations, indicating that component integration does not alter channel geometry or flow characteristics. The versatility of the platform is further illustrated through the insertion of an electrode-functionalized module enabling electrically induced particle displacement under continuous flow. These results demonstrate a practical strategy for combining optical accessibility, robust sealing, and functional adaptability within a single SLA-fabricated microfluidic platform.