Hydroxyapatite (HAp) Thin-Film Coating on Glass Substrates — Process & Preliminary Results

We are excited to share new progress from our biomaterials surface engineering studies. Using a controlled ultrasonic spray coating approach, we successfully deposited high-quality hydroxyapatite (HAp) thin films on glass substrates.
This work represents an important step toward advanced surface functionalization for biomedical applications.

1) Precursor Chemistry & Stoichiometry
To achieve a stable and biologically relevant HAp phase, the precursor solution was prepared with:
· Ca/P ratio: 1.67
· Calcium source: Ca(NO₃)₂·4H₂O
· Phosphate source: (NH₄)₂HPO₄
· Solution concentration: 0.1 M
This composition ensured uniform ionic distribution and promoted controlled HAp formation during deposition.

2) Ultrasonic Spray Coating Parameters
The coating process was performed using a high-frequency ultrasonic atomizer for precise droplet control.
Applied parameters:
· Nozzle frequency: 100 kHz
· Spray rate: 5 cc/min
· Deposition time: 8 min (for 4 pieces glass)
· Total sprayed volume: 40 cc
· Substrate temperature: 300 °C
These conditions enabled efficient solvent evaporation, minimized cracking, and allowed the formation of dense and uniform films.

3) Morphology & Surface Quality
Initial observations indicate films with:
· excellent surface uniformity,
· dense, crack-free microstructure,
· strong substrate adhesion,
· well-controlled porosity.

4) Next Step: Coating on Titanium (Ti) Surfaces
Following the promising results on glass, we are now moving toward the next stage:
Hydroxyapatite coating on titanium surfaces.
This phase will focus on:
· metal–ceramic interfacial behavior,
· adhesion strength and surface energy,
· crystallinity and phase evolution,
· post-annealing structural modifications.
Ti surface coatings are highly relevant for:
· orthopedic and dental implants,
· bone regeneration interfaces,
· advanced biomedical device surfaces.

5) Stay tuned
We will soon share AFM images, microstructural analysis, and the first results from the Ti substrate coatings. Advancing step by step toward scalable, high-performance, biologically compatible coating technologies.