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- ItemFunctional thin films synthesized from liquid precursors by combining mist chambers and atmospheric-pressure plasma polymerization(Basel : MDPI, 2021) Barillas, Laura; Makhneva, Ekaterina; An, Sehoon; Fricke, KatjaFor the creation of thin films, the use of precursors in liquid phase offers a viable alternative when these chemicals are sensitive to high temperatures and phase changes. However, it requires appropriate liquid handling and deposition technologies capable of dispensing the fluid homogeneously to produce a uniform thin film. We report different tailor-made mist chamber designs integrated in an atmospheric-pressure plasma polymerization process for the synthesis of functional thin polymer films from liquid precursors. A systematic investigation, evaluated by performance indicators, is presented on the characteristics and suitability of metallic 3D-printed mist chambers depending on inner volume, geometry and surface post-treatment, for the deposition of a thin liquid monomer film. To assess the quality of the subsequently obtained plasma-polymerized (pp) films, their properties were characterized in terms of thickness, chemical composition, surface morphology and stability in aqueous environment. It was found that the specification of the mist chambers along with the plasma process parameters influences the pp film’s thickness, surface morphology and degree of monomer conversion. This study is one of the first demonstrations of a controllable process able to tune the cross-linked polymeric chains of plasma-polymers at atmospheric pressure, highlighting the opportunities of using mist chambers and plasma technology to discover tailored organic thin films to materials sciences and life sciences.
- ItemGas-discharge plasma-assisted functionalization of titanium implant surfaces(Baech : Trans Tech Publications Ltd., 2010) Schröder, Karsten; Finke, Birgit; Polak, Martin; Lüthen, Frank; Nebe, Barbara; Rychly, Joachim; Bader, Rainer; Lukowski, Gerold; Walschus, Uwe; Schlosser, Michael; Ohl, Andreas; Weltmann, Klaus DieterA crucial factor for in-growth of metallic implants in the bone stock is the rapid cellular acceptance whilst prevention of bacterial adhesion on the surface. Such contradictorily adhesion events could be triggered by surface properties. There already exists fundamental knowledge about the influence of physicochemical surface properties like roughness, titanium dioxide modifications, cleanness, and (mainly ceramic) coatings on cell and microbial behavior in vitro and in vivo. The titanium surface can be equipped with antimicrobial properties by plasma-based copper implantation, which allows the release and generation of small concentrations of copper ions during contact with water-based biological liquids. Additionally, the titanium surface was equipped with amino groups by the deposition of an ultrathin plasma polymer. This coating on the one hand does not significantly reduce the generation of copper ions, and on the other hand improves the adhesion and spreading of osteoblast cells. The process development was accompanied by physicochemical surface analyses like XPS, FTIR, contact angle, SEM, and AFM. Very thin modified layers were created, which are resistant to hydrolysis and delamination. These titanium surface functionalizations were found to have either an antimicrobial activity or cell-adhesive properties. Intramuscular implantation of titanium samples coated with the cell-adhesive plasma polymer in rats revealed a reduced inflammation reaction compared to uncoated titanium. © (2010) Trans Tech Publications.
- ItemModeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane(Dordrecht : Springer Science + Business Media B.V., 2021) Loffhagen, Detlef; Becker, Markus M.; Czerny, Andreas K.; Klages, Claus-PeterA time-dependent, spatially one-dimensional fluid-Poisson model is applied to analyze the impact of small amounts of tetramethylsilane (TMS) as precursor on the discharge characteristics of an atmospheric-pressure dielectric barrier discharge (DBD) in argon. Based on an established reaction kinetics for argon, it includes a plasma chemistry for TMS, which is validated by measurements of the ignition voltage at the frequency f=86.2kHz for TMS amounts of up to 200 ppm. Details of both a reduced Ar-TMS reaction kinetics scheme and an extended plasma-chemistry model involving about 60 species and 580 reactions related to TMS are given. It is found that good agreement between measured and calculated data can be obtained, when assuming that 25% of the reactions of TMS with excited argon atoms with a rate coefficient of 3.0×10−16m3/s lead to the production of electrons due to Penning ionization. Modeling results for an applied voltage Ua,0=4kV show that TMS is depleted during the residence time of the plasma in the DBD, where the percentage consumption of TMS decreases with increasing TMS fraction because only a finite number of excited argon species is available to dissociate and/or ionize the precursor via energy transfer. Main species resulting from that TMS depletion are presented and discussed. In particular, the analysis clearly indicates that trimethylsilyl cations can be considered to be mainly responsible for the film formation.
- ItemEvaluation of osseointegration of titanium alloyed implants modified by plasma polymerization(Basel : MDPI AG, 2014) Gabler, C.; Zietz, C.; Göhler, R.; Fritsche, A.; Lindner, T.; Haenle, M.; Finke, B.; Meichsner, J.; Lenz, S.; Frerich, B.; Lüthen, F.; Nebe, J.B.; Bader, R.By means of plasma polymerization, positively charged, nanometre-thin coatings can be applied to implant surfaces. The aim of the present study was to quantify the adhesion of human bone cells in vitro and to evaluate the bone ongrowth in vivo, on titanium surfaces modified by plasma polymer coatings. Different implant surface configurations were examined: titanium alloy (Ti6Al4V) coated with plasma-polymerized allylamine (PPAAm) and plasma-polymerized ethylenediamine (PPEDA) versus uncoated. Shear stress on human osteoblast-like MG-63 cells was investigated in vitro using a spinning disc device. Furthermore, bone-to-implant contact (BIC) was evaluated in vivo. Custom-made conical titanium implants were inserted at the medial tibia of female Sprague-Dawley rats. After a follow-up of six weeks, the BIC was determined by means of histomorphometry. The quantification of cell adhesion showed a significantly higher shear stress for MG-63 cells on PPAAm and PPEDA compared to uncoated Ti6Al4V. Uncoated titanium alloyed implants showed the lowest BIC (40.4%). Implants with PPAAm coating revealed a clear but not significant increase of the BIC (58.5%) and implants with PPEDA a significantly increased BIC (63.7%). In conclusion, plasma polymer coatings demonstrate enhanced cell adhesion and bone ongrowth compared to uncoated titanium surfaces.
- ItemOne-Step Liquid Phase Polymerization of HEMA by Atmospheric-Pressure Plasma Discharges for Ti Dental Implants(Basel : MDPI, 2021) Buxadera-Palomero, Judit; Fricke, Katja; Reuter, Stephan; Gil, Francisco Javier; Rodriguez, Daniel; Canal, CristinaDental implants can fail due to various factors, in which bad tissue integration is believed to have a significant role. Specific properties of the implant surface, such as its chemistry and roughness, are of paramount importance to address specific cell responses, such as the adsorption of proteins, as well as the adhesion and differentiation of cells, which are suitable for biomaterial and tissue engineering. In this study, an acrylate-containing coating was produced on titanium surfaces through the atmospheric pressure plasma treatment of a liquid precursor, 2-hydroxyethyl methacrylate. A hydrophilic coating was obtained, showing retention of the monomer chemistry as assessed by FTIR analysis and XPS. Enhanced fibroblast adhesion and decreased Staphylococcus aureus and Escherichia coli adhesion were recorded, showing that this is a suitable method to produce biocompatible coatings with a reduced bacterial adhesion.