Meniscus-Guided Interfacial Ring-by-Ring Assembly for In Situ Fabrication of Tubular Hydrogels

The fabrication of arteriole-scale blood vessel-like structures remains a critical barrier in engineering thick, vascularized tissues. Despite advances in artery-scale tubular scaffolds and capillary-scale networks, creating tubular structures at the arteriole scale (50 µm-1 mm) remains challenging because of the intrinsic softness of hydrogels. Here, we present an optofluidic additive-manufacturing method based on meniscus-guided interfacial polymerization within microchannels. Surface tension forms a stable oil-hydrogel interface, where ultraviolet (UV) irradiation selectively polymerizes the hydrogel precursor into ring-like structures. Sequential ring formation along the channel enables in situ assembly of hollow tubular constructs with inner diameters precisely controlled by the axial irradiation position. The method is further extended to biologically relevant softer hydrogels, and UV attenuation analysis and PBS incubation support the structural uniformity and stability of the fabricated tubes. Hydrogel tubes with straight, curved, and branching configurations are fabricated using corresponding microchannel architectures. Multi-material tubular structures with radial and axial compositions are also realized while reducing material-switching steps and waste. Furthermore, synchronizing real-time meniscus detection with UV irradiation enables continuous ring formation and smooth tube walls. This method provides a versatile platform for constructing arteriole-scale vascular-like hydrogel structures with controlled geometries, stability, and material compositions.