An environmentally friendly plasma amination process for the activation of polymers prior to electroless metallization using dielectric barrier discharges (DBD) at atmospheric pressure was investigated. One focus of the work was on the correlation between plasma parameters and palladium coverage on the polymer on the one hand and the palladium coverage and adhesion of a galvanic copper metallization on the other hand. Using XPS spectroscopy it was found that a DBD treatment of polyimide (PI) films with mixtures of N2 and H2 leads to considerably higher Pd surface concentrations than on untreated reference samples or foils treated in air‐DBD. The Pd coverages achieved result in peel strengths of a copper metallization of up to 1.4 N · mm−1.

The interest in applications of atmospheric‐pressure plasmas to solve surface‐technological tasks was originally motivated primarily by the expectation that major cost savings could be achieved if plasma‐based processes, conventionally run below 1 mbar, could now be performed at ambient pressure. However, it was soon recognized that, working at 1 bar, also completely new techniques are made feasible by the utilization of microdischarges, thanks to strongly reduced mean free paths of plasma constituents. The present contribution gives an overview of a number of possibilities, studied in the recent years, to apply atmospheric‐pressure microplasmas for the patterned coating or surface modification of two‐ and three‐dimensional substrates.

A novel plasma stamp has been developed allowing selective plasma treatment and coating of flat surfaces using dielectric barrier discharges at atmospheric pressure. The stamp consists of a flat carrier material covered with photoresist. The resist is structured to form cavities in which the plasma is burning. The cavity footprint is the desired structure to be reproduced or “plasma printed” on the substrate. Cavities can have any geometry and widths down to 10 µm. It is shown that the substrate surfaces can be activated in the same scale as the cavity dimensions and that the treated areas reproduce the footprint of the cavities. To be able to coat surfaces selectively, the stamp consists of multiple resist layers forming a channel network. Using this network, the cavities can be filled with process gas containing polymerizable monomers. This plasma stamp technology introduces a new MEMS process with high potential for production processes and bioscience applications.

To cite this version: Abstract:In modern medicine human mesenchymal stem cells are becoming increasingly important.However, a successful cultivation of this type of cells is only possible under very specific conditions. Of great importance, for instance, are the absence of contaminants such as foreign microbiological organisms, i.e. sterility, and the chemical functionalization of the ground on which the cells are grown. As cultivation of these cells makes high demands, a new procedure for cell cultivation has been developed in which closed plastic bags are used. For adherent cell growth chemical functional groups have to be introduced on the inner surface of the plastic bag. This can be achieved by a new, atmospheric-pressure plasma based method presented in this paper. The method which was developed jointly by the Fraunhofer IST and the Helmholtz HZI can be implemented in automated equipment as is also shown in this contribution.Plasma process gases used include helium or helium-based gas mixtures (He + N 2 + H 2 ) and vapours of suitable film-forming agents or precursors such as APTMS, DACH, and TMOS in helium. The effect of plasma treatment is investigated by FTIR-ATR spectroscopy as well as surface tension determination based on contact angle measurements and XPS spectroscopy.Plasma treatment in nominally pure helium increases the surface tension of the polymer foil due to the presence of oxygen traces in the gas and oxygen diffusing through the gaspermeable foil, respectively, reacting with surface radical centres formed during contact with the discharge. Primary amino groups are obtained on the inner surface by treatment in mixtures with nitrogen and hydrogen albeit their amount is comparably small due to diffusion of oxygen through the gas-permeable bag, interfering with the plasma-amination process.Surface modifications introducing amino groups on the inner surface turned out to be most efficient in the promotion of cell growth.3

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