e-CAP: Engineering Cold Atmospheric Plasmas

Plasmas have been called the fourth state of matter - the other three being solids, liquids and gases. Although this may sound exotic they are actually becoming increasingly common. Plasmas are found in flat screen TV and fluorescence tubes, and they are also used in industry to make computer chips. Plasmas are made up of atoms and molecules that carry electric charges. As a result, they are in a highly unstable state and that means that they desperately want to react with something. This offers huge possibilities for numerous practical uses. Today plasmas are beginning to be used to change livings cells, polymers and even human skin! For plasmas to be useful, they need to be close to room temperature and such plasmas are referred to as cold plasmas . Most cold plasmas are generated under vacuum, and vacuum plasmas are both expensive and inconvenient. There is now a way of making cold plasmas in the open air. These new plasmas are often known as cold atmospheric plasmas or CAP. They are cheaper and easier to use than vacuum plasmas, and are set to revolutionise many applications in both industry and medicine. Controlling cold atmospheric plasmas is challenging; if you want to make them stable they tend not to be very reactive and when they are made reactive - by introducing oxygen into them for example - they tend not to be stable! Significantly the efficiency of their applications relies on how reactive they are, and the controllability of their application processes relies on how stable they are. Therefore it is important to develop cold atmospheric plasmas that are sufficiently reactive AND stable, and this is referred to as the stability-reactivity challenge of cold atmospheric plasmas. We want to address the stability-reactivity challenge for radiofrequency cold atmospheric plasmas. This will lead us towards getting to the heart of understanding cold atmospheric plasmas. As engineers, we believe that if we can better understand plasmas they will be put to many more uses in the future. We propose an ambitious strategy that embraces techniques in several different disciplines of science. By integrating plasma physics, biology and reaction chemistry, we will be able to harness knowledge-pockets of CAP science so as to enable, for the first time, a coherent understanding of the stability-reactivity relationship. This is supported by a novel biology-based approach to characterise plasma reactivity and by sophisticated mathematical modelling tools to unravel plasma stability mechanisms. Furthermore, we aim to fundamentally improve the stability-reactivity relationship through engineering innovation to manipulate the dynamics of plasma production. This will be achieved through novel plasma excitation schemes using pulsed and high radiofrequency voltage rather than the usual sinusoidal voltage nominally at 13.56MHz. The proposed work is confidently expected to produce a major advance in both CAP science and its technological capabilities. This work should help achieve an immense range of applications. It is not possible to list here all the possible uses that cold atmospheric plasmas may have, but one that we are particularly excited about is food decontamination. Perhaps you remember the food scare around October 2004 that centred round the use of lettuce dressing in hamburgers sold in fast food restaurants. The lettuce was contaminated with dangerous bacteria called Salmonella. Salads are notoriously difficult to make safe. You cannot use heat, which is the normal way we have of dealing with bugs. Who would want to eat a limp looking excuse for a salad that had its temperature increased even for a short while? The work we want to do with spores will teach us how to make plasmas more deadly to bugs and that could lead to more efficient ways of making lettuce and other fresh foods safe.