Biomedical coatings prepared by magnetron sputtering

Event Abstract Back to Event The atomic ordering and its correlation to protein adsorption on biocompatible metal oxide coatings Phaedra Silva-Bermudez1, 2, Margarita Rivera3 and Sandra E. Rodil2 1 Instituto Nacional de Rehabilitación, Tissue Engineering, Cell Therapy and Regenerative Medicine Unit, Mexico 2 Universidad Nacional Autónoma de México, Instituto de Investigaciones en Materiales, Mexico 3 Universidad nacional Autónoma de México, Instittuto de Física, Mexico Introduction: Biomaterials that can, simultaneously, direct an adequate biological response and meet biomechanical requirements are essential for dental implants. Coatings are interesting options to tailor the surface properties of mechanically-adequate bulk materials and, consequently, their biological response. Correlations between biological response and surface properties such as roughness (Ra), chemistry or wettability have been widely studied; however, the atomic ordering (AO) and surface free energy (SFE) effects are less understood[1],[2]. The use of amorphous (a-) and crystalline (c-) coatings can confer novel nanotopographies or SFE to materials and constitute controlled models to study the biological effects of specific surface properties; e.g. it is possible to modify the Ra or the wettability while keeping the surface chemistry. One of the first events occurring upon material-biological media interaction is protein adsorption, which influences the development of cell-surface interactions. Thus, in this study, c- and a- ZrO2 and TiO2 coatings, biocompatible oxides of interest for dental implants, were used to study the correlations among atomic ordering, surface properties and protein adsorption. Bovine Serum Albumin (BSA) was used as model protein. Materials and Methods: a- and c- ZrO2 and TiO2 thin films were deposited on Si substrates by Reactive Magnetron Sputtering in Ar/O2 atmosphere, from Zr or Ti targets. Substrates were heated to 250°C or 300°C during deposition to obtain c-ZrO2 and c-TiO2, respectively. Coatings surface properties (AO, wettability, SFE, Ra and chemical composition) were characterized by X-ray Diffraction, Contact Angle, Atomic Force Microscopy, Profilometry, Ellipsometry (ELP) and X-ray Photoelectron Spectroscopy (XPS). Coatings samples were immersed in BSA solutions and a set of ELP angles was acquired in-situ every 2 s at 3 eV for 2400 s. At equilibrium, ELP spectra (1.5-4.2 eV) were acquired and fitted to a four phase optical model to obtain the adsorbed BSA surface mass concentration. Then, samples were rinsed, dried in N2 and analyzed by XPS to quantify the adsorbed protein through analysis of C 1s and N 1s energy regions. Statistical significance was examined by ANOVA with Bonferroni’s modification. Results and Discussion: Coating roughness and water contact angle (WCA) increased with atomic ordering; more notoriously for a-TiO2 and c-TiO2. Different morphologies were observed for c- and a- coatings. Coatings had similar SFE; mainly dispersive with a small polar contribution (γAB). The highest and the smallest γAB were observed for a-TiO2 and a-ZrO2, respectively. γAB was mainly basic (γ_) for all coatings but c-TiO2 with γAB of acidic nature (γ+). A higher BSA adsorption was observed on c- oxides than on their corresponding a- oxides. BSA adsorption was higher on ZrO2 than on TiO2, independently of the atomic ordering. Conclusions: The higher BSA adsorption on c- coatings, compared to the a- ones, seems to be chemistry-related: on TiO2, it may be, mainly, due to an increment of electrostatic interactions between BSA and c-TiO2; γ+ for c-TiO2 > γ+ for a-TiO2. On ZrO2, it may be due to the higher available surface area (Ra) on c-ZrO2 than on a-ZrO2. Coadsorption of H2O and BSA molecules on TiO2 may explain the smaller BSA adsorption on TiO2 than on ZrO2, independently of the atomic ordering. This presents the possibility to tailor specific molecules/ions adsorption through modifying the coatings atomic ordering. Acknowledgements to the financial funding from CONACYT under the research Grant CONACyT-CB-152995 and from DGAPA under the research Grants DGAPA-PAPIIT-IG100113, DGAPA-PAPIIT-IN118814 and DGAPA-PAPIIT-IN118914

The physicochemical properties of an enhanced adsorbent material generated by clays and fungal biomass can be modified systematically. We used spectroscopic techniques to investigate the interaction mechanisms between biomass and clay and how surface properties change with synthesis temperature and clay amounts. Biomass-clay complexes were synthesized and either shock-frozen and freeze-dried or dried at 60 °C in the oven. Surface and bulk properties were analyzed by scanning electron microscopy, attenuated total reflectance-Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and by wettability and surface charge measurements. Interactions of specific biomass-related molecules with clay and changes in physicochemical properties were observed. Higher amounts of clay caused a decrease in particle aggregation while the biomass arranged more evenly. XPS proved interactions due to exchange reactions between Na from the clay and biomass external organic compounds. FTIR, wettability, surface charge, and XPS indicated a less ordered arrangement of the biomass on the clay when drying was performed at 60 °C. The properties of these types of materials define their potential use in future applications. These results indicate the possibility of the selective creation of bioclays: more hydrophobic, with a higher content of organic matter or more specific functional groups on the surface.

Bulk, surface and blood-contacting properties of polyether polyurethanes modified with polydimetnylsiloxane macroglycols

Many industrial processes involve the modification of surfaces. The semiconductor and microelectronics industries are extremely reliant upon surface processing [1], but other applications include solar cells, MEMS and microfluidics, thermal barrier coatings, and fuel cells. Optical measurements are commonly used to indirectly quantify the surface and bulk properties of materials. Unlike direct imaging methods, in which the local surface topography is visualized, indirect methods provide information on surface and bulk properties which are averaged over the entire area being sampled. Typically, a beam of light is directed at the surface to be measured, and the light interacts with the surface to produce the reflected or diffracted light that is then measured by a photodetector. One advantage of indirect measurement techniques is that they are non-invasive, and therefore can be used in extreme or harsh processing environments such as vacuum chambers and reaction vessels by passing the light through windows. These in situ optical sensors have been used for process control of film thickness and chemical composition. However, many more microscopic and nanoscale surface properties can be measured and potentially controlled using optical sensors. The barriers include the difficulty of modeling the optical response, the difficulty of inverting these relationships to robustly infer surface properties, and the practicality of including windows on the chamber to enable optical access. However, to create precise nanostructures in a high-throughput manufacturing setting, real-time measurement and control will be required, and optical sensors are expected to play a significant role.

Silicon nitride and silicon nitride-based ceramics have several favorable material properties, such as high hardness and good wear resistance, which makes them important materials for the coating industry. This thesis focuses the synthesis of silicon nitride, silicon oxynitride, and silicon carbonitride thin films by reactive magnetron sputtering. The films were characterized based on their chemical composition, chemical bonding structure, and mechanical properties to link the growth conditions to the film properties. Silicon nitride films were synthesized by reactive high power impulse magnetron sputtering (HiPIMS) from a Si target in Ar/N 2 atmospheres, whereas silicon oxynitride films were grown by using nitrous oxide as the reactive gas. Silicon carbonitride was synthesized by two different methods. The first method was using acetylene (C 2 H 2 ) in addition to N 2 in a Si HiPIMS process and the other was co-sputtering of Si and C, using HiPIMS for Si and direct current magnetron sputtering (DCMS) for graphite targets in an Ar/N 2 atmosphere. Langmuir probe measurements were carried out for the silicon nitride and silicon oxynitride processes and positive ion mass spectrometry for the silicon nitride processes to gain further understanding on the plasma conditions during film growth. The target current and voltage waveforms of the reactive HiPIMS processes were evaluated.

Controlling preferential growth of chromium – Nitrogen R-HiPIMS and R-DCMS films by substrate magnetic biasing

A novel functional layered diamond like carbon coating for orthopedics applications

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The development of advanced deposition technologies is continuously evolving for the synthesis of oxide coatings used in optical applications. Recent progress is made in the use of magnetron sputtering to reactively deposit metal-oxide thin films. The sputter deposition parameters are chosen with respect to the reaction kinetics of the metal-oxide system to enable a variation of composition along the film growth direction. The key process parameter to control is the sputtering rate of the target. The shape of the composition profile directly corresponds to the preselected variation of deposition rate. By simply varying the sputtering rate using a working gas that consists of an inert-oxygen mixture, structures are synthesized with composition profiles which can be either abrupt or graded in the growth direction. The result is a compositionally modulated structure of the metal-oxide system. This procedure for composition modulated synthesis is demonstrated for metals which are highly reactive with oxygen as well as for those metals which are not. The development of this deposition methodology will facilitate the design of metal oxide films for optical applications, as in gradient-index filters for example. Results are presented for the reactive sputter deposition of metal oxide coatings in the yttrium-oxide, molybdenum-oxide, and copper-oxide systems.

TiN thin films are widely used as protective and decorative coatings for tools in industry. Previous studies have focused on the deposition of TiN coatings on substrates by reactive magnetron sputtering, whereas the use of TiN targets avoids problems such as ‘nitrogen contamination’ and ‘target poisoning’. TiN coatings were grown on silicon wafers and cemented carbide substrates by varying the parameters of the magnetron sputtering plasma source, operating Ar pressure and deposition temperature. The experimental results show the better mechanical properties of ceramic materials deposited using radio frequency (RF) magnetron sputtering. During RF magnetron sputtering, the hardness of the coating increased significantly to 17 Gpa when the deposition working pressure was reduced from 1.5 Pa to 0.5 Pa. The coefficient of friction tends to decrease as the deposition temperature increases, and at 400 °C the coefficient of friction between the deposited film and the friction pair made of Al2O3 material is only 0.36. The nano-scratch experimental tests concluded that the TiN coatings deposited at 300 °C conditions had the best adhesion to the substrate at an Ar pressure of 0.5 Pa under an RF source.

Surface tension method is a simple and popular method to study the surface as well as bulk properties of nonionic surfactants, including Brij‐35, which is a poly‐oxyethylated surfactant. In this study, the surface tension of the solutions of Brij‐35 in the presence of sodium nitrate and sodium sulfate in binary mixed media of alcohol–water was measured precisely. The alcohols used in this study were methanol, ethanol, and propan‐1‐ol. The surface properties such as surface excess concentration ( Γ max ) and minimum surface area ( A min ), bulk properties such as critical micelle concentration (CMC) and packing parameter (P), and thermodynamic properties and of micellization of the surfactant were determined using the surface tension data. The presence of inorganic salts is found to decrease the CMC of Brij‐35 in water–alcohol‐mixed media, whereas the presence of short‐chain alcohols separately increases the CMC values of Brij‐35. The alkyl part of the short‐chain alcohol also plays a significant role in the micellization of Brij‐35. The results were explained on the basis of molecular and ionic interactions, including ion–ion, ion–solvent, hydrophobic, and hydrophilic, among the various species in the system.

Phase separation in NiCrN coatings induced by N2 addition in the gas phase: A way to generate magnetic thin films by reactive sputtering of a non-magnetic NiCr target

The paper presents the results of preliminary research on the possibility of synthesizing ZnO-TiO2 mixed coatings by plasma electrochemical oxidation (PEO). The aim of the work was to synthesize TiO2-ZnO mixed coatings on a titanium substrate from an electrolyte containing ZnO nanoparticles (NPs) and to assess the parameters of PEO on the structure, chemical composition, and properties of the obtained oxide coatings. The PEO process was carried out under various current–voltage conditions using different signals: DC, DC pulse, and AC. In this work, optimal conditions for the PEO process were determined to obtain well-adhering oxide coatings with the highest possible content of ZnO. The structure and morphology of the resulting oxide coatings were investigated, and their chemical and phase composition was comprehensively examined (EDX, XRD, XPS, and GD-OES). In addition, their basic optical properties were assessed. It has been shown that in the PEO DC pulse process, it is possible to obtain oxide coatings characterized by a high degree of structure order, high ZnO content in the oxide coating (3.6 at.%, XPS), and prospective applications for photocatalytic purposes (3.12 eV).

Technological advancements and changing global needs drive deposition techniques, widely used for altering surface properties of components. The crosswinds from global technological advancements in the mobility and power sectors have piqued the interest in sustainable renewable energy tapping devices. Thin aluminium oxide (Al2O3) films are highly valued for various applications in the manufacturing industry, such as cutting tool coatings, optics, energy, and microelectronics. A novel and facile approach has been adopted in the present work to fabricate an oxide-based thin film on a BK7 glass substrate. The aluminium oxide film is deposited by reactive radio frequency (RF) magnetron sputtering by impinging adequate argon to oxygen ratio in a high vacuum environment. Furthermore, Al2O3 is deposited by an alumina target with the same deposition technique, and the results were compared. A digital thickness monitor (DTM) is used to assess the thickness of the deposited film for both processes. The films were first characterized by X-ray diffraction and then analysed by other characterization methods, including Scanning Electron Microscopy, Atomic Force Microscopy, Tribometer and Nanoindentation, and UV-visible spectroscopy. The results indicated that Al2O3 deposited by reactive RF magnetron sputtering performed better in terms of surface morphology, UV-absorbance, nanohardness, and wear resistance and is therefore, more reliable and sustainable when compared with non-reactive RF magnetron sputtering.

Physical vapour deposition of complex hard coatings on ceramic substrates