Interactions between micro-plasma devices

Plasma - the 4th state of matter - is an ionized gas exhibiting collective phenomena. The outstanding role of plasmas in our daily lives remains largely hidden; many products could not exist without plasmas. They underlie technologies, such as TV-displays, mobile phones, solar-cells, nano-chip fabrication, aerospace applications, high-efficiency lighting, biomedicine, cancer treatment, etc. Plasmas are, therefore, often referred to as nano-scale engineering tools of the future.Both fascinating fundamental scientific issues and the enormous social impact that result from their applications drive the field of plasma science and technology. The unique property of low temperature plasmas lies in the fact that the plasma species are not in thermodynamic equilibrium. These plasmas consist of electrons, ions and neutrals. Electron temperatures are around 10000 - 50000 K, while the heavier ions and neutrals are around room temperature. The 'hot' electrons can provide a unique active chemical environment in a cold gas. This offers the facility for precise treatment and modifications of surfaces - even temperature sensitive surfaces such as semiconductors or bio-materials.Particularly challenging and at the same time highly promising is the emerging field of so-called micro-plasmas operated at ambient atmospheric pressure. Micro-plasmas are confined to dimensions on a micro-metre scale and are at present probably the 'hottest' topic in low-temperature plasma science. One can envisage the development of inexpensive disposable micro-plasma sources. High concentrations of radicals can be provided at low gas temperatures without complicated vacuum equipment, e.g. for sterilization and cancer treatments under atmospheric pressure conditions. These areas are frontier technologies with enormous future industrial benefit and social significance.The proposed project, on fundamental investigations of interaction mechanisms between multiple micro-plasmas, provides extraordinary opportunity to lift this research area to its next level. A key issue in understanding fundamental processes, towards their intelligent use for tailoring plasma properties, is insight into power coupling and plasma sustainment mechanisms. There has been some recent progress in understanding single micro-plasma devices, but the interaction of multiple micro-plasma devices is far more complex. In multiple devices, e.g. micro-plasma arrays, single devices interact with each other and their coupling can result in pattern and structure formation. Detailed studies of relevant interaction mechanisms are absent but crucial for further developments and exploitations of micro-plasma arrays. The key to understanding the interaction is to investigate details of energy transport mechanisms. Important factors are the individual roles of energy carrying particles (electrons, ions, radicals, metastables), radiation transport and photo-ionization, and material dependent surface reactions.Measurements on micro-plasmas are extremely challenging due to their very small structures (micron scale) and the collision dominated high-pressure environment requiring exceptionally high temporal resolution down to pico-seconds. Essential diagnostics are newly available modern optical diagnostic techniques and laser spectroscopy - both with pico-second resolution. The most promising approach is exploiting the synergy of these ultrafast diagnostic techniques and state-of-the-art numerical computer simulations.