Reaching beyond the surface in plasma treatments

Low temperature atmospheric pressure plasmas have emerged in recent years as a new powerful technology for a wide range of biomedical applications. The potential therapeutic value of these plasmas has already been demonstrated for applications ranging from sterilization of medical equipment to new cancer treatments. With animal and clinical trials underway, the hopes for this new technology are high and the field is developing very rapidly

Emerging applications of low temperature gas plasmas in the food industry

The global burden of foodborne disease due to the presence of contaminating micro-organisms remains high, despite some notable examples of their successful reduction in some instances. Globally, the number of species of micro-organisms responsible for foodborne diseases has increased over the past decades and as a result of the continued centralization of the food processing industry, outbreaks now have far reaching consequences. Gas plasmas offer a broad range of microbicidal capabilities that could be exploited in the food industry and against which microbial resistance would be unlikely to occur. In addition to reducing the incidence of disease by acting on the micro-organisms responsible for food spoilage, gas plasmas could also play a role in increasing the shelf-life of perishable foods and thereby reduce food wastage with positive financial and environmental implications. Treatment need not be confined to the food itself but could include food processing equipment and also the environment in which commercial food processing occurs. Moreover, gas plasmas could also be used to bring about the degradation of undesirable chemical compounds, such as allergens, toxins, and pesticide residues, often encountered on foods and food-processing equipment. The literature on the application of gas plasmas to food treatment is beginning to reveal an appreciation that attention needs also to be paid to ensuring that the key quality attributes of foods are not significantly impaired as a result of treatment. A greater understanding of both the mechanisms by which micro-organisms and chemical compounds are inactivated, and of the plasma species responsible for this is forming. This is significant, as this knowledge can then be used to design plasma systems with tailored compositions that will achieve maximum efficacy. Better understanding of the underlying interactions will also enable the design and implementation of control strategies capable of minimizing variations in plasma treatment efficacy despite perturbations in environmental and operational conditions

Reaching beyond the surface in plasma treatments

Cold atmospheric pressure plasmas have been shown to possess bactericidal potential. Many research groups are looking into developing biomedical applications for plasma; however some big questions still remain. There are several main hurdles that need to be jumped before plasma has a chance to break through into the medical treatments market, one of these is penetration. Can plasma penetrate beyond the surface and reach cells beyond those on the surface? Can we make plasma treatments to penetrate, for example, through skin

Cold atmospheric-pressure plasma treatment for promotion of cell adhesion onto PDMS substrates

This research aims to develop a cell coating on polydimethylsiloxane (PDMS) to study the response of corneal epithelial cells to mechanical stress. PDMS is a highly hydrophobic silicone elastomer, which despite its excellent mechanical properties is an unattractive surface for cell adhesion. In order to promote cell adhesion onto PDMS, a cold atmospheric-pressure plasma treatment has been used to modify the surface properties of the PDMS without affecting its bulk mechanical characteristics

Plasma-induced inactivation of a reference micro-organism

Research related to non-thermal atmospheric pressure plasma sources and technologies is currently focused on emerging applications in medicine and biology. As in any other plasma application, the efficacy of the plasma treatment depends on various discharge operating conditions such as discharge geometry, dissipated power and feed gas composition, all of which influence chemical and physical processes in the discharge. In addition, attention needs to be paid to the various methods in which biological ‘targets’ are prepared and presented to the plasma as these can have a profound influence on the treatment efficacy. Currently, different laboratories around the world use a wide variety of plasma devices and microbiological techniques, making a direct and quantitative comparison of experimental results virtually impossible

Atmospheric-pressure plasma surface activation for solution processed photovoltaic devices

Atmospheric solution based processes are being developed for the fabrication of thin film photovoltaic devices. Deposition techniques such as electrodeposition, spin coating, spraying or printing are promising techniques to increase the throughput and reduce the cost per Watt of Copper-Indium-Gallium-Selenide (CIGS), Copper-Zinc-Tin-Sulphide (CZTS) and perovskite thin film solar technologies. All these technologies require pre-treatment of the substrate prior to the deposition of the thin film and ideally this pretreatment should also be performed at atmospheric pressure. Results presented in this paper show that use of an atmospheric-pressure plasma is highly effective in activating the surface of substrates commonly used in thin film photovoltaic (PV) device fabrication. Surface activation improves the adhesion of thin films. The use of an atmospheric activation process is compatible with a continuous vacuumfree PV fabrication process. Soda lime glass (SDL) and fluorine doped tin oxide (FTO) coated glass are substrates commonly used in the fabrication of photovoltaic modules. These substrates have been surface treated using a He/O2 atmospheric-pressure plasma, resulting in increased surface energy as evidenced by Water Contact Angle (WCA) measurements. The pre-treatment reduces adventitious surface contamination on the substrates as shown using X-ray Photoelectron Spectroscopy (XPS) measurements. The advantages of using the atmospheric plasma surface pre-treatment has been demonstrated by using it prior to atmospheric deposition of Cadmium Sulphide (CdS) thin films using a sonochemical process. The CdS thin films show pinhole-free coverage, faster growth rates and better optical quality than those deposited on substrates pre-treated by conventional wet and dry processes

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster]

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster

Study of plasma-induced inactivation of a reference micro-organism

We present a result of an ongoing European initiative (European COST Action MP 1101) that aims to create a reference plasma system and a biological reference protocol for the study and comparison of plasma treatments across laboratories. Endospores of Bacillus subtilis ATCC 6633 are proposed as reference microorganism as they can be stored for long periods without loss of viability, serving as a common starting point for experiments performed in different locations and at different times. To avoid problems related to shadowing effects, a monolayer of spores are deposited onto filter membranes using a vacuum filtration technique and these are then exposed to different plasma systems. In this study, sample preparation protocols and bactericidal properties of a dielectric-barrier surface discharge are reported upon

Characterisation of an atmospheric-pressure air DBD discharge

Combining the advantages of non-equilibrium plasmas with the ease of atmospheric-pressure operation, dielectric barrier discharges (DBD) are widely used in many fields and applications, including ozone production, sterilization, tumour treatments and surface modification

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster]

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster