What is plasma?
The "fourth state of matter" explained simply
Plasma is a fascinating phenomenon that is often referred to as the fourth state of matter – alongside solid, liquid and gaseous. But what exactly is plasma? In physics, it is an ionised gas. This means that so much energy is added to a gas that the electrons detach from the atoms or molecules. This creates an electrically conductive mixture with free electrons and ions. The term "plasma" (from the Greek for "formed") was coined in 1928 by Nobel Prize winner Irving Langmuir.
Because it consists of charged particles, plasma reacts strongly to electric and magnetic fields. It often glows because excited particles emit light, which is also used in many types of lamps.
Important note: The physical plasma referred to here should not be confused with blood plasma in medicine or cell plasma in biology.
A general distinction is made between two types of plasma:
- Hot plasmas: Here, the temperature of all particle types is so high that the entire plasma is extremely hot and almost all gas particles are ionised. Examples include the interior of the sun or welding arcs and nuclear fusion reactors.
- Cold plasmas (low-temperature plasmas): In these plasmas, only the electrons are very energetic (hot), while the gas itself remains comparatively cool. Cold plasmas are found in many technical applications, e.g. surface technology or medicine.
Plasma in nature: Everywhere in the universe
Plasma is not an exotic laboratory phenomenon. It is the most common state of visible matter in our universe! Over 99 percent of visible matter exists in a plasma state.
Stars and the sun
Our sun and all other stars consist of plasma.
Lightning
Lightning is an impressive example of plasma. The enormous electrical discharge ionises the air, which then glows and emits the typical light.
Aurora borealis
The colourful aurora borealis occurs when charged particles from the solar wind enter the Earth's atmosphere and excite the gas molecules to glow, creating plasma.
Ionosphere
A layer in the upper atmosphere that is ionised by solar radiation.
Plasma in everyday life and technology:
invisible helpers
Less obvious, but ubiquitous, are the technical applications of plasma. Many products we use every day would not exist without plasma technology.
Lighting
Fluorescent lamps generate light through gas discharge plasmas.
Electronics
The manufacture of microchips and flat screens would be unthinkable without plasma processes. Plasma is used to etch and coat tiny structures.
Surface finishing
Scratch-resistant spectacle lenses, anti-reflective camera lenses and thin protective coatings are applied using plasma processes such as plasma sputtering.
Metal processing
In welding and cutting, an electric arc, which is also a form of plasma, is used to generate heat for melting or cutting metal.
Everyday objects
Plastic packaging is pre-treated with plasma to make it printable. Medical packaging and even food are biologically decontaminated with cold plasma.
The potential of plasma: Future technology from Greifswald
Plasma research is a dynamic and forward-looking field.
- Plasma medicine: Cold plasmas can kill germs and accelerate wound healing. Plasma therapy devices developed at the INP are already being used successfully to treat chronic wounds.
- Environmental technology: Plasma can be used to purify water and air.
- Sustainability: Plasma technology offers solutions for more sustainable agriculture and the energy transition.
- New materials: Plasma processes can be used to produce specific coatings and nanomaterials, e.g. for improved electrolysers.
The Leibniz Institute for Plasma Science and Technology (INP) in Greifswald is the largest non-university plasma research institute in Europe. We develop new plasma sources and processes to solve the challenges of tomorrow.
Also in Greifswald, the Max Planck Institute for Plasma Physics (IPP) is dedicated to nuclear fusion: the Wendelstein 7-X stellarator experiment is researching how hot plasma can be magnetically confined to generate clean energy through nuclear fusion – similar to what happens inside the sun.
Conclusion: Plasma is a fascinating phenomenon – omnipresent in nature and technology. From the glowing northern lights in the sky to medical applications for wound healing, plasma encounters us in a wide variety of forms. Plasma research at the INP not only provides exciting insights into a unique state of matter, but also tangible innovations for medicine, the environment and technology.
