Activation reactions of molecules in plasma are investigated using plasma polymerization of hexamethyldisiloxane as a model system for plasma‐state polymerization. Underlying reaction pathways and film‐forming mechanisms are revisited based on a simplified macroscopic approach, considering the average energy available per monomer particle, Epl, in relation to the threshold energy, Eth, which represents an activation barrier for plasma polymerization. Basic principles are discussed involving averaged values for collision frequency, cross‐section, and reaction rate to produce film‐forming species combining macroscopic and microscopic quantities. Considering the energy uptake from the electric field by the electrons, the energy transfer from electrons to monomer molecules, and the conversion into film‐forming species, it is demonstrated that Epl/Eth is equally relevant as the electron energy distribution function for plasma‐chemical activation reactions.

The surface functionalization of electrospun nanofibers allows for the introduction of additional functionalities while at the same time retaining the membrane properties of high porosity and surface-to-volume ratio. In this work, we sequentially deposited layers of chitosan and alginate to form a polyelectrolyte complex via layer-by-layer assembly on PLGA nanofibers to introduce pH-responsiveness for the controlled release of ibuprofen. The deposition of the polysaccharides on the surface of the fibers was revealed using spectroscopy techniques and ζ-potential measurements. The presence of polycationic chitosan resulted in a positive surface charge (16.2 ± 4.2 mV, pH 3.0) directly regulating the interactions between a model drug (ibuprofen) loaded within the polyelectrolyte complex and the layer-by-layer coating. The release of ibuprofen was slowed down in acidic pH (1.0) compared to neutral pH as a result of the interactions between the drug and the coating. The provided mesh acts as a promising candidate for the design of drug delivery systems required to bypass the acidic environment of the digestive tract.

Microwave plasmas at atmospheric pressure are used for surface treatments like for example cleaning, sterilization or decontamination purposes, for a pre-treatment to increase the adhesion of lacquer, paint, or glue, and for the deposition of different kind of layers and coatings. Micro plasma jets can also be applied for biomedical applications and for treatment of small and complex geometries like for example the inside of capillaries. Larger plasma torches which exhibit higher gas temperatures can also be used for chemical syntheses like waste gas decomposition, methane pyrolysis, or carbon dioxide dissociation and for plasma spraying purposes. In the present publication an overview on the development and the investigation of the operating principle of two atmospheric pressure microwave plasma torches at frequencies of 2.45 GHz and 915 MHz will be presented. The plasma sources are based on a cylindrical resonator combined with coaxial structures. To explain how these plasma sources work, simulations of the electric field distribution will be discussed. Furthermore, some physical characteristics of an air and an Ar/H2 atmospheric plasma like gas temperatures, excitation temperatures and densities as well as the heating of the plasma by the microwave will be investigated.

Revealing threshold energies in plasma polymerization processes with hydrocarbons by measuring the specific energy input (per monomer molecule) in low- and atmospheric-pressure plasmas.