Continuous bath embedded bioprinting for high-fidelity biofriendly fabrication of complex tissues

One Sentence Summary By dynamically generating locally confined microbaths, continuous bath embedded bioprinting (CBEB) achieves high-precision, low-shear fabrication of complex, multicellular tissue architectures with minimal material consumption. • Multi-nozzle layer-wise shell and bath printing achieves shape-conforming fabrication using ultrashort nozzles. • Ultrashort single and convergent nozzles demonstrate superior positioning accuracy and minimized shear stress history. • The process is ideal for high-cell-density printing and conserving precious support materials. High-fidelity fabrication of complex living tissues remains a challenge in regenerative medicine. Conventional embedded bioprinting relies on static baths and long nozzles, which introduce significant positioning errors, fluidic delays, and high material waste. Here, we propose continuous bath embedded bioprinting (CBEB), a strategy that transforms the support bath from a static reservoir into a dynamically generated, locally confined medium. By cyclically depositing a “shell-bath-bioink” trilayer, CBEB enables the use of ultrashort nozzles (∼3 mm), effectively suppressing nozzle deformation-induced errors to below 1 μm and reducing bath consumption by ∼ 68%. Compared to stepwise methods, CBEB significantly improves dimensional precision (0.22 mm vs. 0.82 mm error) and structural stability. Utilizing photosensitive collagen (NorCol) and multi-material switching, we successfully fabricated complex architectures including vascular networks, heart valves, and a miniaturized heart model. The printed cardiomyocytes maintained > 80% viability after 7 days. By redefining the mechanical and rheological foundations of embedded printing, CBEB provides a scalable, high-precision platform for constructing hierarchical functional tissues.