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Non-planar Extrusion Bioprinting For Creating Strain-stiffening Semilunar Valve Leaflets
Benjamin Albert, Coral Wang, Christian Williams, Jonathan Butcher, PhD.
Cornell University, Ithaca, NY, USA.

OBJECTIVE: The emergence of embedded bioprinting as a tissue engineering method has strengthened the ability to replicate the complex geometry and heterogeneity of heart valves. Embedded printing methods expand manufacturing approaches because of the print bath support. Currently, printing multi-material geometries such as heart valves is an inefficient process because of extruder switching and curved structure. The development of non-planar slicing may allow for high quality printing of heart valves with tunable behavior.
METHODS: A custom 3D print slicer was developed to allow for non-planar embedded bioprinting (BENT). The slicer creates print paths along the curvature of a desired surface and repeats the pattern to create three dimensional structures. A two material print was created of a simple M shape with three distinct layers. The print was printed with alginate using both planar and BENT slicing. Additionally, corrugated samples of alginate were created with 0, 22.5, and 45 degree angles. The printed samples were stretched to 20% strain on our custom tensile test mechanism. Last, a curved, trileaflet structure was printed with alginate into a support bath using BENT printing to demonstrate capabilities in creating heart valve structure.
RESULTS: BENT printing created the M print with distinguished layers, no stringing, and little oozing; the planar print displays all three of these deficiencies (A). The stress response of the three corrugated prints show distinct differences; 45 degree prints show strain stiffening response (B). Leaflet printing shows high fidelity in curvature and orifice from initial heart valve geometry prints (C).

CONCLUSIONS: Initial results show that non-planar printing can significantly increase fidelity in multi-material printing and produce accurate heart valve leaflet structure with tunable properties. Future work will study use of this method on cell viability and overall function of complete heart valve models.


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