Water-based hydroxyapatite photocurable feedstock for the manufacture of architectured parts by vat photopolymerization

Abstract

Hydroxyapatite (HAp) is a biocompatible, osteoconductive, and biodegradable material widely studied for tissue engineering applications. Additive manufacturing, particularly vat photopolymerization technologies, enable the manufacture of custom-made, highly precise solutions. In this work, a colloidal approach was used to develop a water-based photocurable HAp-loaded feedstock with low viscosity, high solid loading (45 vol%), and low amount of organic compounds (10 vol%). Two distinct types of dispersants were evaluated to modify the surface of the HAp powders to enhance stability and dispersion. Rheological experiments were conducted to determine the optimal dispersant concentration, solid-loading, and pre-polymer content. Photorheological experiments were also performed to identify the printing parameters suitable for the vat photopolymerization technology. This work’s approach, characterized by its low organic content, enabled a fast-debinding process (≈13.5 h) when compared to the conventional photocurable ceramic-based feedstock. Different sintering temperatures were tested (1150 °C → 1350 °C) and X-ray diffraction was used to evaluate the crystallographic composition at each temperature. Additionally, the relative density of the sintered parts was calculated and the compressive strength determined. The results demonstrated that sintering temperature enables high customization to meet specific end-user requirements. Architectured structures with interconnected porosity were successfully printed as a proof-of-concept of the potential printability of the developed aqueous-based feedstock. The eco-friendly photopolymerizable feedstock developed in this work should strongly impact the production cycle of resorbable bioceramic-based components.