Biominerals formed by organisms in the course of biomineralization often demonstrate complex morphologies despite their single-crystalline nature. This is achieved owing to the crystallization via a pre-deposited amorphous calcium carbonate (ACC) phase. Inspired by this natural strategy, we utilized robocasting, an additive manufacturing 3D-printing technique, for printing 3D objects from novel long-term, Mg-stabilized ACC pastes with high solids loading. We demonstrated, for the first time, that the ACC remains stable for at least a couple of months, even after printing. Crystallization, if desired, occurs only after the 3D object is already formed and at temperatures significantly lower than those of common post-printing sintering (Figure 1). We also examined the effects of different organic binders on the crystallization, morphology, and amount of incorporated Mg.
Figure 1. (A) XRD patterns of the CaCO3 pastes collected following the storage in acetone excess for 48 and 96 h (at a wavelength of Cu K-a 1.5406 Å). (B) ACC 3D-printed models forming the word “ACC”.
By utilizing the robocasting method, we present an innovative route to the bio-inspired 3D printing of high Mg-ACC. We also introduce a novel storage protocol that allows to maintain the amorphous nature of ACC powder for at least several days. In contrast to current technologies, our approach involves sintering at near-ambient temperatures and on-demand crystallization. We also examined the influence exerted by different organic binders on the crystalline structure and the morphology of the printed model.
We believe that this novel bio-inspired method may pave the way for a new bio-inspired route to low-temperature 3D printing of ceramic materials for a multitude of applications.