Formation process of apatite layer on titanium-coated silicon wafer surfaces

Abstract

Apatite-coated silicon wafers are expected to be utilized for novel biosensors or implants. However, the mechanism and optimum conditions for the formation of an apatite layer on silicon wafer surfaces are unclear. Herein, we examined the effect of pretreating silicon wafers with titanium sputtering and weak alkali aqueous solutions before immersing them in a simulated body fluid (SBF). A week after immersion, silicon wafer surfaces coated with thin titanium layers were covered by hemispherical apatite particles that were produced in a heterogeneous nucleation reaction, whereas untreated silicon wafer surfaces were covered by spherical particles that were produced in a homogeneous reaction. Pretreatment of titanium-coated silicon wafers with 0.1 M NaOH aqueous solution assured heterogeneous apatite formation. Both titanium-coated and untreated silicon wafers were fully covered by the apatite layer after soaking in the SBF for 23 weeks. These findings show that pretreatment of silicon wafers with titanium sputtering and weak alkali aqueous solution is effective for obtaining apatite-coated silicon wafers.

The Use of Simulated Body Fluid (SBF) for Assessing Materials Bioactivity in the Context of Tissue Engineering: Review and Challenges

“…SBF, as well as human blood plasma, is a solution supersaturated with apatite [ 7 ], and, thus, apatite formation on materials occurs as a result of the heterogeneous nucleation and growth of the apatite nuclei that spontaneously proceeds by taking up calcium and phosphate ions in SBF once the apatite nuclei have formed [ 7 ]. It should be noted that homogenous nucleation rarely occurs in SBF, but nevertheless has been reported in several papers [ 70 ]. The apatite nucleation that occurs is affected by both chemical factors such as hydroxyl groups, surface energy and surface charge, as well as physical factors, such as roughness.…”

Xenon Difluoride Dry Etching for the Microfabrication of Solid Microneedles as a Potential Strategy in Transdermal Drug Delivery

“…A decrease in roughness value was previously observed after titanium coating on polished side of silicon wafer (from 0.06 to 0.04 µm). [ 46 ]…”

“…A decrease in roughness value was previously observed after titanium coating on polished side of silicon wafer (from 0.06 to 0.04 µm). [46] The fabrication techniques and processed material have great impact on the surface properties of produced MNs. Hence, the initial roughness value of the material to be processed is vital and is directly associated with the final roughness value.…”

There Are over 60 Ways to Produce Biocompatible Calcium Orthophosphate (CaPO4) Deposits on Various Substrates

“…Examples include thermal treatments [36,37], glow discharge [73][74][75], ultraviolet [49,[75][76][77], and high-energy low-current DC electron beam [78,79] irradiations, as well as electron cyclotron resonance plasma oxidation [80] and laser [81,82] treatments, which together produce very thin surface layers of the substrate with oxidation and/or partial degradation [49,[73][74][75][76][77][78][79][80][81] or surface texturization [82]. More specifically, the surface of substrates can be coated with an interlayer of another compound [48,67,[83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98] containing special binding agents [99][100][101] before the CaPO 4 are deposited. That is, zinc orthophosphate…”

“…More specifically, the surface of substrates can be coated with an interlayer of another compound [48,67,[83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98] containing special binding agents [99][100][101] before the CaPO 4 are deposited. That is, zinc orthophosphate [48], bioglass [88,89], titania [90][91][92], SiC [93], calcium carbonate [94], titanium [95,96] and diamond [97] coatings have been pre-deposited on the surface of various substrates onto which CaPO 4 are subsequently deposited. Similarly, organophosphate polymers have been chemically bonded to chemically inert polyethylene via surface graft polymerization of phosphate-containing monomers [67].…”