Tomographic Printing in a Chip: A Versatile Platform for Biomimetic 3D Organ-on-Chip

Organ‐on‐chip (OoC) platforms are increasingly adopted for predictive in vitro testing. However, most remain limited by soft‐lithography‐derived 2.5D microfluidic architectures and nonphysiological rigid materials, or bioprinting approaches that require complex and failure‐prone post‐fabrication assembly. Here, we present a versatile approach that integrates tomographic volumetric additive manufacturing (TVAM) directly within preassembled microfluidic chips, enabling rapid, contactless fabrication of freeform 3D OoCs. Leveraging our open‐source optical simulation framework, Dr.TVAM, we perform TVAM in custom‐designed chips, eliminating post‐printing manual assembly steps that commonly lead to leakage, contamination, and poor reproducibility. This strategy, termed TVAM‐in‐a‐chip, supports the generation of diverse 3D channel architectures in multiple biocompatible photoresins spanning a wide range of chemistries and mechanical properties, including cell‐laden formulations. We demonstrate multi‐channel designs, compatibility with confocal imaging, and dynamic culture of epithelial and endothelial models. Overall, TVAM‐in‐a‐chip overcomes key limitations of current OoC technologies and paves the way for a new generation of scalable, biomimetic 3D platforms for advanced in vitro modeling.