Deposition and characterization of a dual-layer silicon- and silver-containing hydroxyapatite coating via a drop-on-demand technique

Silicon-containing hydroxyapatite (SiHA) and silver-containing hydroxyapatite (AgHA) have been shown to provide enhanced bioactivity and antibacterial properties over pure hydroxyapatite (HA), respectively. This present work is aimed at developing a dual, nano-structured HA/SiHA-AgHA coating on glass substrates via the Drop-on-Demand (DoD) micro-dispensing technique. In this study, phase-pure nano-HA, nano-SiHA containing 0.8 wt% Si, and nano-AgHA containing 0.5 wt% Ag powders were synthesized in-house, and later used to deposit onto the substrates using the DoD technique, forming the dual HA/SiHA-AgHA coatings. A uniform, phase-pure coating 34.5 ± 1.0 μm thick without any undesirable calcium phosphate phases, was achieved. In addition, several phosphate and hydroxyl bands attributed to apatite, were observed on the coatings. Energy Dispersive X-ray Spectroscopy (EDS) mapping revealed that the elements Si and Ag were observed to distribute evenly throughout the top coating layer, which confirmed the versatility of the DoD technique in the production of such a hybrid coating structure.