Multi-Modal photoFRESH: Light-Pipe Embedded Printing of Heterogeneous Hydrogel and Tissue Architectures

Abstract

Recreating the complex spatial gradients and multi-material transitions of native tissues remains a fundamental challenge in 3D bioprinting. To address this, we introduce multi-modal photoFRESH, which integrates localized photochemistry into embedded printing by delivering light through a fiber-optic light-pipe. By tuning numerical aperture, print speed, and photoabsorber content, we achieve precise layer-by-layer control of crosslinking, stiffness, and bioorthogonal biomolecular tethering while preserving high print fidelity. Both photoactivatable support baths and extruded bioinks can be patterned, together with traditional FRESH printing. Utility of the platform is demonstrated by the fabrication of structurally complex tissue scaffolds and cellularized muscle constructs with distinct mechanical and biochemical domains. This multi-modal approach expands the boundaries of embedded bioprinting toward functional and heterogeneous tissue architectures.