Valve-based consecutive bioprinting method for multimaterial tissue-like constructs with controllable interfaces.

Bioprinting is a promising technology focusing on tissue manufacturing, whose vital problem is the precise assembly of multiple materials. As the primary solution, the extrusion-based multi-printhead bioprinting (MPB) method could cause material interface defects and inefficient motion time during multimaterial switching. We present a valve-based consecutive bioprinting (VCB) method to resolve these problems, containing an integrated precise switching printhead and a well-matched voxelated digital model. The rotary valve isolates the bio-inks' elastic potential energy in the cartridge from precision interface assembling based on the Maxwell viscoelastic model. We study the coordinated control approach of the valve rotation and pressure adjustment to actualize the seamless switching, leading to a controllable multimaterial interface, including boundary and suture. Furthermore, we compare the VCB method and MPB method, quantitatively and comprehensively, indicating that the VCB method obtained greater mechanical strength (increased by 44.37%) and higher printing efficiency (increased by 29.48%). As an exemplar, we fabricate a muscle-like tissue with vascular tree and suture interface encapsulating C2C12 and human dermal fibroblasts (HDFB) cells, then placed in complete medium with continuous perfusion for five days. Our study suggests that the VCB method is sufficient to fabricate heterogeneous tissues with complex multimaterial interfaces.