Surface modification of starch based biomaterials by oxygen plasma or UV-irradiation

Radiation is widely used in biomaterials science for surface modification and sterilization. Herein, we describe the use of plasma and UV-irradiation to improve the biocompatibility of different starch-based blends in terms of cell adhesion and proliferation. Physical and chemical changes, introduced by the used methods, were evaluated by complementary techniques for surface analysis such as scanning electron microscopy, atomic force microscopy, contact angle analysis and X-ray photoelectron spectroscopy. The effect of the changed surface properties on the adhesion of osteoblast-like cells was studied by a direct contact assay. Generally, both treatments resulted in higher number of cells adhered to the modified surfaces. The importance of the improved biocompatibility resulting from the irradiation methods is further supported by the knowledge that both UV and plasma treatments can be used as cost-effective methods for sterilization of biomedical materials and devices.I. P. thanks the FCT for providing her a postdoctoral scholarship (SFRH/BPD/8491/2002). This work was partially supported by FCT, through funds from the POCTI and/or FEDER programs, The European Union funded STREP Project HIPPOCRATES (NNM-3-CT-2003-505758) and the European NoE EXPERTISSUES (NMP3-CT-2004-500283)

Verfahren und Vorrichtung zur plasmachemischen Reinigung von Substraten

The invention relates to a device and a process for the plasma-chemical cleaning of substrates by means of a low-temperature low-pressure plasma, by which water or an aqueous gas mixture is used as the plasma gas. This permits the removal of the various impurities from a wide variety of substrate materials. For example, metals, semiconductor products, organic and unorganic polymers and non-metallic unorganic materials can be cleaned. Moreover, impurities such as oils, greases, plastic residue, burnt-in, resinified oils, oxides, grinding and polishing agents can be removed

Plasmafeinreinigen. Perspektiven

The present article provides a survey of the use of low-pressure plasma plants for cleaning and the pretreatment of solvent and aqueous-alkaline processes, where even anorganic pollutions may be partly eliminated as well. Frequently, however, a wet chemical cleaning is still indispensable

Analysis and modeling of gas-phase processes in a CHF3/Ar discharge

The present work deals with the diagnostics of fluorocarbon plasmas by different experimental methods and complementary numerical analysis of the plasma. The plasma diagnostics were performed with non-invasive methods. In this paper, we present results obtained by laser-induced fluorescence and UV absorption measurements. The complementary numerical simulations accounted for the electron-neutral interactions, discharge dynamics, and chemical reactions. Several insights were obtained from the combined experimental and numerical approaches, especially concerning the conclusiveness of the results and previous observations from the literature. As important initial neutral species, CF 3 and H originate from electron collisions with CHF3. The atomic hydrogen is responsible for fluorine abstraction reactions which result in the formation of hydrofluoric acid as well as in unsaturated carbon bonds. It was found from the simulations that in the examined discharges, this reaction is the most important channel for the high-rate production of the CF molecule in the gas phase via CF2 + H ? CF + HF. For this molecule, no anisotropy in the density was found and the production solely occurs in the gas phase. Contrary to that, the production of CF2 via the abstraction of fluorine from CF3 in the gas phase was found to be of less importance for the overall concentration of this molecule. Instead, chemical reactions at the chamber walls which release CF2 were identified experimentally as major sources. According to the simulations, the unsaturated fluorocarbon molecules react to oligomers, such that the net reaction can be roughly described by nCHF3 ? (CF2)n + nHF. A good agreement between the simulated and the experimentally observed densities and rates was obtained, which confirms the interpretation of the ongoing plasma-chemical processes as well as the underlying physical discharge parameters consistently. Fluorocarbon plasmas are applied in several industrial branches. They can be either used for etching in the semiconductor industry or for coating of surfaces with low-k dielectric, hydrophobic and oleophobic polymer films. The net-result -etching or deposition- depends on the fluorine to carbon ratio and thus, on the plasma chemistry. Despite of the successful application of fluorocarbon plasmas in the industry, several details about the chemical kinetics are still a matter of discussion. In particular, this accounts for the kinetics of CF2

Deposition rate and three-dimensional uniformity of RF plasma deposited SiOx films

The variation of power, pressure and O2/HMDSO ratio in an RF plasma was carried out to examine deposition rates and to optimize SiOx film properties for the coating of polymers. The deposition rate can mainly be increased with monomer gas flow, whereas it is independent of pressure. Pure HMDSO plasmas reveal different internal conditions and deposition rates compared to gas mixtures of O2 and HMDSO. Empirically obtained deposition models for the used symmetrical plasma reactor are given. Investigations on the three-dimensional (3D) uniformity of quartz-like coatings on polycarbonate blocks with and without recesses were performed. The deposition rate depends on the dimensions of the 3D-formed parts when depositing in front of the RF electrode. A higher pressure and use of power modulation can improve the coating uniformity in fissures

PACVD-derived thin films in the system Si-B-C-N

PACVD has been used to obtain SiBCN thin films for the first time at low temperatures (250 °C) from a single-source precursor. In comparison with PACVD BCN, the B:C ratio is the same, but there is a slightly increased N content, and the presence of Si improves the hardness and adhesion characteristics. XPS and FTIR results suggest that most Si atoms are bonded to N and C, with the C being mainly sp2/sp3 hybridized C[BOND]C and C[BOND]N bonds, while B is bonded to N, also with sp2/sp3 hybridization