Bio-inspired 3D printing of layered structures utilizing stabilized amorphous calcium carbonate within biodegradable matrices†

Many composites in nature are formed in the course of biomineralization. These biocomposites are often produced via an amorphous precursor such as amorphous calcium carbonate (ACC), demonstrating a layered structure. In the current study, robocasting, a 3D-printing technique, was used to print layered structures inspired by the mineralized tissues of Ophiomastix wendtii and Odontodactylus scyllarus, which exhibit a layered organization. Various biodegradable organic matrices with a high percentage (>94%) of ACC reinforcements were compared, and their mechanical properties were studied. With the organic matrix protection, ACC was stabilized for long periods, exceeding even three years, when stored at ambient conditions. The layered structures were printed and fractured using the three-point bending method to evaluate their strength. The fracture interface was examined to weigh the benefits an amorphous precursor may offer in the 3D printing processes of ceramic materials. The fracture interface presented bulk behavior with no distinct layering, resembling the formation of mineral single crystalline tissue in nature and overcoming one of the most critical challenges in 3D printing, namely the inter-layer interfaces. Herein, a bio-inspired, low-temperature route to form layered structures is presented. By fusing the layers together following low-temperature sintering, a composite structure composed of stabilized ACC integrated with biodegradable, environmentally friendly matrices can be obtained.