Embedded bioprinting with multiscale on-demand sub-voxel assembly for integrated coordination

<h2>Summary</h2> Extrusion-based bioprinting struggles to replicate the cross-scale heterogeneity of native tissues, where micron-scale features must integrate seamlessly within centimeter-scale architectures. We present multiscale on-demand sub-voxel assembly for integrated coordination (MOSAIC), an embedded bioprinting framework that enables dynamic programming of internal filament patterns, referred to as sub-voxels, synchronized with global geometry during continuous printing. MOSAIC combines a physics-informed model of multi-material filament formation and hierarchical path planning to achieve controlled heterogeneity from approximately 0.03 cm micro-patterns to 2 cm structures in a single uninterrupted process. We demonstrate this capability through anatomically inspired constructs: a dual-layer artery model integrating soft-to-stiff gradients for physiological compliance and an intestinal model combining micro-scale villi and millimeter-scale folds with spatially organized cells. This approach expands the design space of embedded bioprinting, overcoming static material constraints and enabling efficient fabrication of multiscale architectures that are critical for advanced tissue models.