ICMCTF2011 Session D1-2: Bioactive and Biocompatible Coatings and Surface Functionalization of Biomaterials

Superhydrophobic and superhydrophilic surfaces are benifical in many biomedical applications. Here, we report a method of producing both superhydrophilic and superhydrophobic surfaces on titanium substrates. Sandblasting the titanium surfaces with alumina particles, followed by dip-coating in a colloidal silica nanoparticle solution, produces a superhydrophilic surface with a water contact angle (WCA) of less than 5°. Further chemical modification with a fluorinated-carbon film, deposited by introduction of C₄F₈ gas under the action of plasma in a deep reactive ion etcher, renders the surface superhydrophobic, with a WCA in excess of 150°. These surfaces are characterized by WCA measurements, scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and surface profilometry. In addition, the hydrophilic and hydrophobic stability of these surfaces is discussed.

Titanium is a commonly used implant material because of its inertness and biocompatibility in e.g. orthopaedic applications. However, there is still a need for a faster healing process and improved fixation of implants. Strontium has demonstrated positive effects as a bioactive agent due to its anti-inflammatory and anti-osteoporotic properties.

Strontium-containing titanium films (thickness ~100 nm) were synthesized by magnetron co-sputtering from a pure 2-inch Ti target and a composite 2-inch Ti-Sr (80-20 at.%) target. The pure Ti target was run in DC mode, whereas the composite Ti-Sr target was run in pulsed DC mode in order to avoid target poisoning. Prior to deposition of Ti-Sr, an initial layer of pure titanium (thickness ~100 nm) was deposited onto the Si(001) substrates. During the depositions, the substrates were electrically floating. The amount of strontium in the coatings was varied by the relative power to the two targets by means of which strontium surface concentrations, as determined from XPS, ranging from 0 to 20 at.% were obtained. X-ray diffraction revealed a predominantly amorphous film structure, except in the case of pure titanium; high contents of strontium yielded completely amorphous Ti-Sr films. Furthermore, the effects of strontium concentration on the film morphology and surface topography were studied by cross-sectional SEM and AFM, respectively. Cell proliferation tests (1, 2, 4, 7 days) of the strontium-containing titanium surfaces were carried out with human dental pulp stem cells (hDPSCs), and the correlation between the proliferation of the hDPSCs and the strontium concentration was investigated.

In this work a coating layer of Ti/TiN/nc-TiN/a-Si₃N₄, were deposited on Stainless steel M340 and Ti6Al4V substrates using DC and RF codeposition reactive magnetron sputtering technique. Characterization, mechanical and corrosive tests were conducted with the purpose of establish the possibilities to use it as a biomaterial in the body, including: XRD and XPS techniques to analyze the structure and composition of coatings, profilometry to analyze the topography of substrates, films and wore Surfaces (tribologicaly tested), scratch test to evaluate film adhesion to the substrate and electrochemical technique as well as a reciprocating tribocorrosion test in 1% NaCl water solution and artificial saliva solution, to evaluate the corrosion susceptibility under static and reciprocating conditions respectively. All the results are analyzed and discussed. The tests suggest that this multilayer is a promising biomaterial for biomedical applications.

Shape memory alloys (SMAs) offer a unique combination of novel properties, such as shape memory effect, super-elasticity, biocompatibility and high damping capacity. In the present study, NiTiCu and NiTiAg shape memory alloy thin films were successfully grown on Si(100) substrates by dc magnetron sputtering technique. Crystalline structure, hardness and phase transformation properties of NiTiCu and NiTiAg films were investigated using X-ray diffraction (XRD), nanoindentaion and four probe resistivity methods. Further, aim of the study was to deposit hard and adherent nanocrystalline NbN protective layer on NiTiCu and NiTiAg films to improve their surface, mechanical and corrosion properties without sacrificing the phase transformation and shape memory effect. The structural, electrical and mechanical studies were performed on both NbN/NiTiCu and NbN/NiTiAg films and the results were compared. Further the application of NbN/NiTiCu and NbN/NiTiAg films in the electrochemical sensing of dopamine, which has critical physiological importance in the Parkinson’s disease has also been demonstrated.