Mechanical Alloying and High-Repetition-Pulsed-Laser based Manufacturing Method for Nanostructured Hydroxyapatite Films on Cobalt-Chromium and Nylon Substrates

Abstract

We report a high repetition rate picosecond laser-based additive manufacturing process to coat nanoscale rough hydroxyapatite (HA) on cobalt chromium plates (CoCr). Nanoscale rough coatings of hydroxyapatite are desirable. They mimic the naturally formed hydroxyapatite and provide very high surface area and surface roughness, leading to better cell adhesion cell-matrix interaction. Nanoscale HA powders undergo the synthesis process using the sol-gel procedure and ball milling. Ball-milled powders are suspended in volatile solvents and coated on the CoCr surface using picosecond laser irradiation. The chemical composition and morphology of the coated material is characteristic of electron microscopy. The laser-assisted fusion process results in HA coatings with hierarchical surface roughness down to nanometer scale, enhancing the CoCr implants' biocompatibility. Besides, we report a manufacturing process for coating nanostructured and hierarchically porous Hydroxyapatite (HA) films on cobalt-chromium (CoCr) substrates. The preparation of HAP’s Nanoparticles occurs using three different methods: ball milling of sol-gel synthesized HAP, mechanical alloying of calcium oxide (CaO) and diammonium phosphate (DAP), and mechanical alloying of eggshell and diammonium phosphate. The nanoparticle's characterization proved the presence of nanophase HAP in sol-gel synthesized powders and synthesis of apatite phases in mechanically alloyed powders. Small droplets of nanoparticle ethanol suspensions were injected on the substrate and irradiated with high-repetition-rate picosecond pulsed laser to coat the CoCr samples. Characterization of the deposited films showed bonding of HAP nanoparticles to a film with nanostructured morphology and hierarchical porosity and the incorporation of CoCr from the substrate into the first few deposited layers of HAP nanoparticles. The two-step manufacturing process results in bioactive and biocompatible HAP films with a desirable morphology for biological cells' growth and infiltration. Finally, the study of Hierarchically Porous Nylon 6 substrate Hydroxyapatite (H.A.) films and nanostructured development was examined and reported. When formulating the HAP nanoparticles, three methods are available for use. These methods include calcium oxide (CaO), sol-gel synthesized HAP, and diammonium phosphate (DAP) mechanical alloy. During the study, it was discovered that characterizing nanoparticles showed that nanophase HAP existed in three different forms, and the synthesis of the apatite phase happened in mechanically alloyed powders. In the experiment, nanoparticle methanol suspension was added dropwise in the substrate. It was then irradiated with a picosecond pulsed laser. This was done to cover the Nylon 60 samples. After which, the deposited films were characterized for purposes. These include revealing if HAP nanoparticles can attach to a film of nanostructured morphology and porosity and, finally, to check if nylon from substratum can be absorbed in the deposited layers of HAP nanoparticles. These two-step manufacturing methods used result in bioactive and biocompatible HAP films, which have a morphology that allows the biological cell to infiltrate and grow.