Molecular dynamics study on bonding mechanism of 3D printing of bone scaffolds

In order to understand the bonding mechanism of hydroxyapatite (HA) particles for the 3D printedbone scaffolds with binders, the performance of three commercial binders i.e. PVP, PAM and PVAwas studied by means of molecular dynamics simulationin terms of cohesive energy density, binding energy and pair correlation function g(r), as well as mechanical properties. The results revealed that the relationship of the binding energies between the HA surface with the three binders is consistent with their cohesive energy densities, i.e. PAM>PVA>PVP. The analysis of g(r) indicated that the interfacial interactionof HA and binders could mainly be attributed to the ionic bonds and hydrogen bonds which formed between the polar atoms, functional groups in binder polymer and the Ca, -OH in HA, and the strength of ionic bonds is larger. TheYoung's modulus for the three interaction types of binders/HA can be ranked as the following sequence: PVA/HA>PAM/HA>PVP/HA, which are all inferior to that of the single HA. This conclusion is not completely consistent with the ranking of the relevant binding energies, which means that there is no specific intrinsic relation between the mechanical properties of the three binding types and the related viscidity of binders.