Plasma - its nature and use
What is a plasma?
The term “plasma” in the public is often associated either with a constituent of blood serving as a liquid carrier for blood cells or nuclear fusion for power generation or with television technology (“plasma tv”). Only the latter two of these examples lead onto the right track with respect to the IP4Plasma project since “plasma” in these cases means the fourth physical state of matter (the other three are solid, liquid and gas). This state represents a gas containing atoms and/or molecules as in an “ordinary” gas plus some or all of the following: excited atoms, excited molecules, charged particles including positive and negative ions, radicals (these are characterized by the presence of a lonesome electron in the outer valence shell and may therefore be unstable and chemically reactive) and photons or light. Though containing charged particles the plasma as a whole is neutral.
In nature plasmas can occur in very hot environments existing in stars like our sun or in lightnings during a thunderstorm. However, a plasma does not necessarily need a hot environment. This is demonstrated by natural phenomenons produced by charged particles of the solar wind called aurora borealis (north sphere) or aurora australis (southern sphere) occurring mostly at the skys in regions near the earth’s magnetic poles. A beautiful example of an aurora borealis dancing at the sky is shown in the movie by Tor Even Mathisen:
Aurora borealis movie by Tor Even Mathisen
Technical plasmas and their use in the IP4Plasma project
Both hot (expert term: thermal) and cold (expert term: non-thermal) plasmas can also be generated artificially under low as well as ambient pressure conditions for purposes such as the generation of energy in fusion reactors, the generation of light in plasma displays and energy saving lamps, generation of hot arcs used for welding and cutting, chemical analysis of materials using mass spectroscopy, in spacecraft propulsion using ion engines and for the ozone (antibacterial agent) production and treatment of surfaces of materials.
Plasma – the fourth state of matter as a tool for the surface treatment, explained in the award-winning movie “Plasma – a bright advantage”
Focus of the project IP4Plasma project are innovations in the area of surface treatment using cold ambient pressure plasmas to be demonstrated in new processes for the production of medical products including an advanced tuberculosis test and new types of wound dressing. The type of plasma, to become more specific, is a dielectric barrier discharge (DBD) plasma. Such a plasma has been for decades conventionally applied in the so-called corona treatment of plastic film materials before processing steps such as printing or laminating. Treatment is achieved by contacting the polymer surface with the plasma with its reactive components (you may refer here to the previous section ”What is a plasma?”) These react with the polymer and thus modify its surface by changing its chemical and physical nature, e.g. by the attachment of chemical groups. The result may be improved wettability of a polymer film. This is needed, for example, for printing advertisements on plastic bags using aqueous inks. Without the plasma treatment the ink would be easily wiped away on contact with e.g. sweaty hands. Examples for the equipment used can be found e.g. on the website of SOFTAL Corona & Plasma GmbH Without treatment there would be no printability at all or the inks would be wiped off on the slightest contact with the hands.
The potential scope of the ambient pressure plasma technology does, however, extend far beyond the just mentioned and industrially well-established applications, where the surface is treated whole area and without depositing a coating. The technology allows, for example, to apply the plasma treatment selectively on certain surface areas. This is called an area-selective or local treatment.
Also, a so-called film-forming agent (sometimes called “precursors”) may be added to the plasma gas. Under properly chosen conditions this leads to the deposition of a coating on the treated material.
Both whole-area and area-selective treatment with and without deposition of coatings will all be part of the IP4Plasma project development work to provide innovative technology for the industrial production of advanced medical consumable products. These include:
- A new tuberculosis test
- allowing diagnosis within minutes
- with no need for any test equipment installation
- high sensitivity (>80% for TB positive cases detected) and specific (>99%)
- at a cost as low as 1 € for endemic countries and 5 € for Western European
Current tuberculosis tests are costly and include a chest X-ray, microbiological examination, tuberculin skin test, surgical biopsy either individually or in combinations. A cheap and easy to use test as is subject of the development work of this project will help overcome significant obstacles achieve its much more widespread use thus laying the basis for much more effective combat of the tuberculosis disease.
- A low cost human immunodeficiency virus (HIV) test with enhanced sensitivity
- New types of wound dressing
- improved draining properties
- capabilities to control moisture or pH values within the wound
- protection of the wound from infection
- reduced production cost
These three medical applications present demonstrators to show the capabilities of the ambient pressure plasma surface treatment technology in the resource and cost-efficient as well as environmentally-friendly manufacture of high-tech products.