The coatings based on carbon nanotubes (CNTs) are increasingly developed for their applications, among others, in medicine, in particular for implants in implantology, cardiology, and neurology. The present review paper aims at a detailed demonstration of different preparation methods for such coatings, their performance, and relationships between deposition parameters and microstructure and material, mechanical, physical, chemical, and biological properties. The thermal and electrostatic spraying, electrophoretic and electrocathodic deposition, and laser methods are presented. Characterization of microstructure of coatings, topography, morphology, adhesion of CNTs to a substrate, mechanical behavior, corrosion resistance, wettability, cytotoxicity, bioactivity, and antibacterial protection are reviewed for different deposition methods and parameters. The state-of-the-art in the field of carbon nanotubes shows a considerable number of research performed on CNTs coatings. The different forms of CNTs, deposition methods, parameters, and substrates were applied as process variables. The microstructures and surface homogeneity, chemical and phase compositions, mechanical properties at the micro- and nanoscale such as coating Young`s modulus and hardness, interface adhesion strength and delaminating force, open corrosion potential and corrosion current density, contact angle in wettability assessment, and bioactivity, cytotoxicity, and antibacterial efficiency among biological properties were determined. The summary of so far achievements, strengths and weaknesses, and important future research necessary for clarification of some weak points, development of non-toxic, mechanically and chemically resistant, bioactive, and antibacterial multicomponent coatings based on functionalized CNTs are proposed.

Carbon nanotubes are proposed for reinforcement of the hydroxyapatite coatings to improve their adhesion, resistance to mechanical loads, biocompatibility, bioactivity, corrosion resistance, and antibacterial protection. So far, research has shown that all these properties are highly susceptible to the composition and microstructure of coatings. The present research is aimed at studies of multi-wall carbon nanotubes in three different combinations: multi-wall carbon nanotubes layer, bilayer coating composed of multi-wall carbon nanotubes deposited on nanohydroxyapatite deposit, and hybrid coating comprised of simultaneously deposited nanohydroxyapatite, multi-wall carbon nanotubes, nanosilver, and nanocopper. The electrophoretic deposition method was applied for the fabrication of the coatings. Atomic force microscopy, scanning electron microscopy and X-ray electron diffraction spectroscopy, and measurements of water contact angle were applied to study the chemical and phase composition, roughness, adhesion strength and wettability of the coatings. The results show that the pure multi-wall carbon nanotubes layer possesses the best adhesion strength, mechanical properties, and biocompatibility. Such behavior may be attributed to the applied deposition method, resulting in the high hardness of the coating and high adhesion of carbon nanotubes to the substrate. On the other hand, bilayer coating, and hybrid coating demonstrated insufficient properties, which could be the reason for the presence of soft porous hydroxyapatite and some agglomerates of nanometals in prepared coatings.

Titanium implants are commonly used because of several advantages, but their surface modification is necessary to enhance bioactivity. Recently, their surface coatings were developed to induce local antibacterial properties. The aim of this research was to investigate and compare mechanical properties of three coatings: multi-wall carbon nanotubes (MWCNTs), bi-layer composed of an inner MWCNTs layer and an outer TiO₂ layer, and dispersion coatings comprised of simultaneously deposited MWCNTs and nanoCu, each electrophoretically deposited on the Ti13Nb13Zr alloy. Optical microscopy, scanning electron microscopy, X-ray electron diffraction spectroscopy, and nanoindentation technique were applied to study topography, chemical composition, hardness, plastic and elastic properties. The results demonstrate that the addition of nanocopper or titanium dioxide to MWCNTs coating increases hardness, lowers Young’s modulus, improves plastic and elastic properties, wear resistance under deflection, and plastic deformation resistance. The results can be attributed to different properties, structure and geometry of applied particles, various deposition techniques, and the possible appearance of porous structures. These innovative coatings of simultaneously high strength and elasticity are promising to apply for deposition on long-term titanium implants.

Herein a MWCNT/TiO₂ coating was shown to have higher roughness, adhesion strength and corrosion resistance compared to MWCNT, also with high porosity and wettability to support cell adhesion. However, the release of toxic species results in decreased proliferation.

Three coatings suitable for biomedical applications, including the dispersion coating composed of multi-wall carbon nanotubes (MWCNTs), MWCNTs/TiO₂ bi-layer coating, and MWCNTs-Cu dispersion coating, were fabricated by electrophoretic deposition (EPD) on Ti Grade II substrate. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nanoindentation were applied to study topography, chemical, and phase composition, roughness, hardness, Young’s modulus, plastic, and elastic behavior. The results showed that the best mechanical properties in terms of biomedical application were achieved for the MWCNTs coating with titania outer layer. Nevertheless, both the addition of nanocopper and titania improved the mechanical resistance of the base MWCNTs coating. Compared to our previous experiments on Ti13Nb13Zr alloy, a general tendency is observed to form more homogenous coatings on pure metal than on the alloy, in which chemical and phase compositions are more complex.