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Development of a dispensing based additive manufacturing technique for the creation of alginate bone scaffolds

University of British Columbia

Bone scaffolds are used to treat large bone defects. There are noted advantages for moving away from the standard of using human bone to create these scaffolds, and instead making them out of synthetic biomaterials. Dispensing Based Additive Manufacturing (DBAM) provides a method for creating these synthetic bone scaffolds using a biomaterial called alginate. This thesis outlines a method to create synthetic bone scaffolds from alginate using DBAM. First an ink was developed to be used with DBAM, consisting of sodium alginate, calcium carbonate and a photoacid generator. This ink was able to react when exposed to Ultraviolet (UV) light to partially gel, as required between layers in the DBAM process. Studies were conducted to find the ideal concentrations of the components of the ink. The gelation in between layers was modelled to determine the ideal layer thickness, UV lamp intensity and exposure time that would lead to the ideal mechanical properties for a partially gelled layer. The dispensing process was modelled to determine the height and width of an extruded line based on the applied pressure, needle diameter, and needle length. This model has been used to determine the ideal pressure to achieve a desired layer height. A commercial software was used to convert three-dimensional commanded shapes to two-dimensional layer toolpaths. Advanced trajectory techniques have been used to generate a time-based trajectory from these toolpaths that would minimize traversal time, while staying within the velocity, acceleration and jerk limits of the in-house developed Computer Numerical Controlled (CNC) machine. The dispensing was synchronized with the tangential speed of the machine to keep dispensed width constant. Sample parts have been manufactured using the developed DBAM process, with an improved dimensional accuracy and mechanical stiffness in comparison to results reported in literature.

Text

2019-04-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/69902

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/