Simultaneous Multi-material Embedded Printing for 3D Heterogenous Structures

In order to mimic the natural heterogeneity of native tissue and provide a better micro environment for cell culturing, multimaterial bioprinting is becoming a common solution to construct tissue models in vitro. With embedded printing method, complex 3D structure can be printed soft biomaterials with reasonable shape fidelity. However, the current sequential multimaterial embedded printing faces a major challenge, which is the inevitable trade-off between the printed structural integrity and printing precision. Here, we propose a simultaneous multimaterial embedded printing method. With this method, we can easily print a firmly attached and high precision multilayer structure. With multiple individually controlled nozzles, different biomaterials could be precisely deposited in a single crevasse, which minimizes the uncontrolled squeezing and guarantees no contamination of embedding medium within the structure. To achieve this, the dynamics of the extruded bioink in the embedding medium are analyzed both analytically and experimentally, and the effects of printing parameters including printing speed, nozzle angle and rheology of embedding medium on the 3D morphology of the printed filament are quantitively evaluated. Double layer thin-walled structure with each layer less than 200 μm was printed. It was demonstrated that intestine and liver models could be printed with 5% GelMA, crosslinked and extracted from the embedding medium without significant impairment or delamination. The peeling test further proves that proposed method offers a better structural integrity than conventional sequential printing method. The proposed simultaneous multimaterial embedded printing method could serve as a powerful tool to support the complex heterogenous structure fabrication and open unique prospects for personalized medicine.