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Forschergruppe FOR 1123 "Physics of Microplasmas"

Microplasmas - small plasmas at extreme conditions

Microplasmas have gained very high attention recently. Microplasmas are operated at around atmospheric pressure in small volumes with a scale length of typically a few 10 to 100 µm. They are thus highly collisional. Still, due to the con?nement in narrow spaces, they have pronounced non-equilibrium properties with hot electrons but cold gas temperature. They are most useful for a variety of applications.

Traditional concepts fail

Microplasmas can have extreme properties: though the absolute power may be small the power density is enormous. They are characterized by high electron densities and very high electric ?elds close to the surface. The plasma-surface interaction is very intense. The Paschen criterion for ignition may no longer apply. The Debye length contracts below 1 µm, the mean free paths of species become very short. Microplasmas are sensitive to instabilities.

Towards a better understanding of microplasmas

Subject of this Research Unit is a systematic investigation of selected microdischarge con?gurations in order to better understand their complex dynamics from breakdown to full evolution of the discharge. We want to understand the space- and time dependent transport of energy, radiation and reactive species, and the plasma surface interactions under these extreme conditions. Finally, we investigate prototypical applications and the plasma-surface-interactions with the aim to identify and characterize universal properties of microplasmas under these extreme conditions.

Direct contact to living tissue

Apart from the fascination by novel phenomena of plasma physics, microplasmas show an enormous potential for technical applications. Microplasmas allow for the first time to combine two desired properties: to operate processes at ambient pressure and to generate cold non-equilibrium plasmas with controlable chemical processes. This combination opens up new applications as controlled and localized materials synthesis, biomedical procedures where plasmas are in direct contact with living tissue, or new very efficient light sources and detectors. Microplasmas as portable universal tools are approaching the realization.

Controlled modification of large surfaces

The small size of these plasmas allows e.g. a direct mask-less plasma etching of surfaces or a structured local application of functional coatings. Microplasma jets are very well suited for their integration into robots for automated surface structuring. The integration of many single microplasma discharges in devices with some ten thousands single elements (arrays), which can be excited in parallel or addressed, opens up additional interesting applications for the modification of large surfaces. These arrays are produced by micro machining and micro patterning structure techniques.

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