Near-Plasma Chemical Surface Engineering.

As a new trend in plasma surface engineering, plasma conditions that allow more-defined chemical reactions at the surface are being increasingly investigated. This is achieved by avoiding high energy deposition via ion bombardment during direct plasma exposure (DPE) causing destruction, densification, and a broad variety of chemical reactions. In this work, a novel approach is introduced by placing a polymer mesh with large open area close to the plasma-sheath boundary above the plasma-treated sample, thus enabling near-plasma chemistry (NPC). The mesh size effectively extracts ions, while reactive neutrals, electrons, and photons still reach the sample surface. The beneficial impact of this on the plasma activation of poly (tetrafluoroethylene) (PTFE) to enhance wettability and on the plasma polymerization of siloxanes, combined with the etching of residual hydrocarbons to obtain highly porous SiOx coatings at low temperatures, is discussed. Characterization of the treated samples indicates a predominant chemical modification yielding enhanced film structures and durability.

Plasma Processing of Low Vapor Pressure Liquids to Generate Functional Surfaces.

The concept of depositing solid films on low-vapor pressure liquids is introduced and developed into a top-down approach to functionalize surfaces by attaching liquid polyethylene glycol (PEG). Solid-liquid gradients were formed by low-pressure plasma treatment yielding cross-linking and/or deposition of a plasma polymer film subsequently bound to a flexible polydimethylsiloxane (PDMS) backing. The analysis via optical transmission spectroscopy (OTS), optical, confocal laser scanning (CLSM) and scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) as well as by water contact angle (WCA) measurements revealed correlations between optical appearance, chemical composition and surface properties of the resulting water absorbing, covalently bound PEG-functionalized surfaces. Requirements for plasma polymer film deposition on low-vapor pressure liquids and effective surface functionalization are defined. Namely, the thickness of the liquid PEG substrate was a crucial parameter for successful film growth and covalent attachment of PEG. The presented method is a practicable approach for the production of functional surfaces featuring long-lasting strong hydrophilic properties, making them predestined for non-fouling or low-friction applications.