Table 1.

An overview of conventional surface modification methods for Ti and its alloys.

Techniques	Advantages	Limitations
Grit blasting	Low-cost and simple operation	Blasting particle residues, hard to form nanoscale topography
Plasma spraying	Large-scale production, appropriate bioactivity	Low crystallinity, high tensile residual stress, hard to control composition and structure of the coatings
HVOF spraying	Large-scale production, appropriate bioactivity	Moderate crystallinity, moderate tensile residual stress, hard to control composition and structure of the coatings
Cold spraying	Improved bioactivity, suitable for oxygen- and heat-sensitive compounds.	Hard to form nanoscale topography, moderate adhesion of coatings to Ti substrates
PIII&D	Easy composition control, high bonding strength	Hard to form microscale topography, expensive machinery
Acid etching	Low-cost and easy operation	Hard to form nanoscale topography, poor uniformity
Alkali-heat treatment	Low-cost and easy operation, uniform distribution	Time consuming, easy loss of sodium ions under the moisture
Anodization	Uniform nanoscale topography with defined pore diameters	Hard to form microscale topography, moderate bonding strength
Micro-arc oxidation	High strength, micro-hardness and wear resistance	Hard to form nanoscale and suitable topography
Electrodeposition	Low-cost and easy operation, controllable thickness with broad range	Moderate bonding strength, limited coating diversity
Electrophoretic deposition	High deposition rate, controllable thickness with broad range	Uniformity limited by size of particles, hard to form nanoscale topography
Chemical covalent immobilization of biomolecules	Precise immobilization of various biomolecules	Complex operation in some cases, special storage conditions
Layer-by-layer assembly	Simple operation, controllable layered structures	Difficult-to-scale preparation, low bonding to substrates, special storage conditions