Various new plasma‐based surface technological processes are made feasible by localizing atmospheric‐pressure discharges to predefined volumes with sub‐millimeter linear dimensions. So‐called Plasma Printing processes use cold discharges in microcavities formed temporarily by contacting a substrate with a suitably designed kind of plasma stamp. Aside from dielectric barrier discharges driven by mid‐frequency (MF) AC voltages, cold microplasmas can also be sustained in arrangements without a dielectric barrier, if RF excitation is used. The modification or coating of internal surfaces in already sealed microfluidic systems promises the achievement of a wide range of physico‐chemical surface properties which are difficult to attain by wet‐chemical or low‐pressure plasma processes. Using a proper electrode arrangement, the coating or modification can be localized to a selected segment of a microfluidic system.magnified image

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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.

Barrier coatings against plasticizer leaching are deposited on flexible polyvinylchloride (PVC) films typically used in flooring or in the automotive industry. Octamethylcyclotetrasiloxane (OMCTS) and hexamethyldisiloxane (HMDSO) are plasma polymerized using plasma‐activated CVD (PA‐CVD) based on an atmospheric pressure (AP) dielectric barrier discharge (DBD). A reduction in plasticizer leaching higher than 80% is achieved with these coatings. The effect of the monomer flow rate, discharge power, and oxygen flow rate on the barrier efficiency is investigated. The coating composition of the best barrier coating has been identified and the long‐time barrier efficiency in contact with an organic solvent has been studied.

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.