PECVD of silicon and titanium based coatings to enhance the biocompatibility of blood contacting biomedical devices

The clinical success of a surgical implantation depends on various factors including the design and biocompatibility of the biomaterial, surgical procedure adopted, injuries made during implantation and health and condition of the patient. The success of a biomaterial depends on the interaction and the progressive reaction between the blood components and the surface of the implant. Proteins present in the blood will be the first components to become adsorbed on the surface of the biomaterial. Studies show that the protein fibrinogen present in the blood plasma is the major initiator of inflammatory reactions and involved in blood clotting. By minimizing the fibrinogen adsorption it is possible to reduce the contribution of the biomaterial surface characteristics to thrombosis and inflammatory reactions. In this work, silicon and titanium based thin film coatings with four different surface characteristics were deposited by PECVD on 316L stainless steel substrates. Polymer-like SiOxCyHz, silica-like SiOx, titanium oxide TiO, and silicon-titanium mixed oxide coatings were deposited by plasma decomposition of organic molecules. An extensive study was done on silicon based coatings deposited from hexamethyl disiloxane (HMDSO) to analyze the influence of plasma process parameters like RF power, precursor flow ratio and flow rate on the surface chemical and mechanical characteristics of the film. Titanium dioxide coatings deposited from titanium tetraisopropoxide (TIP) were also analyzed for the effect of plasma process parameters on their surface characteristics. Silicon - titanium mixed oxide coatings were deposited to obtain intermediate characteristics between silicon oxide and titanium oxide films and the process was optimized to get a hydrophilic surface with wettability lower than SiO, and a bandgap higher than that of titanium dioxide. It was concluded, from the fibrinogen adsorption studies, that both the film wettability and bandgap has to be optimized in order to minimize the fibrinogen adsorption

Low temperature growth technique for nanocrystalline cuprous oxide thin films using microwave plasma oxidation of copper

We report on the direct formation of phase pure nanocrystalline cuprous oxide (Cu2O) film with band gap ~ 2 eV by microwave plasma oxidation of pulsed dc magnetron sputtered Cu films and the highly controlled oxidation of Cu in to Cu2O and CuO phases by controlling the plasma exposure time. The structural, morphological and optoelectronic properties of the films were investigated. p-type Cu2O film with a grain size ~20-30 nm, resistivity of ~66 Ω cm and a hole concentration of ~2×1017 cm-3 is obtained for a plasma exposure time of 10 min without using any foreign dopants. The optical absorption coefficient (~105 cm-1) of the Cu2O film is also reported

Thin film diffusion barrier formation in PDMS microcavities

We describe a method to form glass like thin film barrier in polydimethylsiloxane (PDMS) microcavities. The reactive fragments for the surface reaction were created from O2 and hexamethyldisiloxane (HMDS) in RF plasma environment. The reaction is based on migration of the reactive fragments into the microcavities by diffusion, to form a glass like thin film barrier to conceal the naked surface of PDMS. The barrier successfully blocked penetration of a fluorescent dye rhodamine B (RhB) into PDMS. The thickness of the barrier could be controlled by the time of reaction and the pressure inside the reaction chamber. There is a wide range of applications of such a technique in various fields, e.g. for coating the covered surfaces of microfluidic channels, tubes, capillaries, medical devices, catheters, as well as chip-integrated capillary electrophoresis and advanced electronic and opto-fluidic packaging

Functionalization of cycloolefin polymer surfaces by plasma-enhanced chemical vapour deposition: Comprehensive characterization and analysis of the contact surface and the bulk of aminosiloxane coatings

The surface science of bioassay devices is of great importance in the development of modern diagnostic platforms. The quality of surface is one of the most important elements of the device, often governing the background response, hence controlling the sensitivity of an assay. Detailed surface characterization and analysis are imperative for the preparation of reproducible coatings with desired properties. We performed a comprehensive characterization of 3-aminopropyl-triethoxysilane films prepared under two different deposition conditions on COP slides. Two sets of slides were prepared, by exposing them to plasma reaction for 30 seconds (A30 slide) and 4 minutes (A4 slide). While the variations in the deposition conditions seemed very subtle, the use of several powerful analytical tools helped us to reveal some fundamental differences between the studied films in terms of binding capacity, swelling and adhesion. Overall, the A30 films, with a thickness of 5.12 nm, showed up to 40% higher binding capacity and 25% better adhesion than the thicker A4 coatings (28.15 nm). Upon contact with aqueous media, a significant change was observed in terms of surface roughness. The A30 slides outperformed A4 slides, resulting in smoother surface, which is an important parameter for biomolecule immobilisation. The use of the techniques described in this article is aimed to set new standards for the characterization and analysis of the substrate surface of the future diagnostic devices. © The Royal Society of Chemistry 2010