Plasma Science and Technology in the Home

Posted on June 5, 2012


Scientific research is an important factor in the analysis of new technologies. It is important to have independent scientific data especially when we are talking about plasma technology. Plasmas are very complex and it is easy to make claims that are not based on true scientific fact.

You can get a more detailed explanation about what a plasma is  in the education section, noting that it not in anyway linked to the biological plasma:

We have all heard of the plasma TV, where small cells within the TV are exposed to an electric field. The gas in the cells break down to form a plasma. The light from the plasma, which is in the UV is used to excite a phosporous screen to give high quality pictures. Different types of phosphors create red, green and blue light to give the color. The plasma TV has excellent picture quality and color definition.

It is not so well known that in a smoke detector, a weak corona plasma is formed and electrical current flows via electrons across the smoke detector. Normally, with no smoke the plasma current is undisturbed and a stable current is reached; but when smoke enters the plasma region the electrons collide with the smoke particles. It is a little like elephants walking on a motorway, suddenly everything goes much slower. The plasma current drops and the smoke alarm is sounded. So plasmas can saves lives even in our house.

A recent new technology uses the same idea of electrons colliding with dust particles. It is called a ionic purifier. When the electrons collide with the dust they stick to the surface, this causes the dust clusters to become negatively charged. The ions also collide with the dust but the ions are much heavier and therefore much slower, so more electrons hit the dust than ions. In a purifier a weak plasma is formed and any dust particles present are charged up negatively. An electric field with a positive and negative side is set up and the dust is attracted to the positive side. The dust is then collected and removed from the air. This is very important as some people are allergic to dust and mites that float in the air.

The weak plasma also has some more useful effects. When the electrons are heated in the electric field they collide with gas atoms and molecules and knock off electrons, this is called ionisation or ionization to our American cousins. But not all electron collisions successfully knock off the electron from the atom, some collisions just shake the atom or molecule and cause the electrons to enter an excited state. These atoms or molecules with excited electrons are called radicals. Radicals can collide with other gas atoms or molecules and form short lived chemicals called metastable states. These metastable molecules or atoms are highly reactive because the electrons are excited and they will react with cells or other living organism, killing them. They do not travel far as they are short lived so the effect is localised but careful design is required to prevent a build up of radicals that might be harmful. Normally, the metastable states quickly decay into harmless air molecules. The weak plasma can excite oxygen and turn it into a sterilizing agent which is short lived. This cleans the air in the purifier of dangerous microbes that could harm your health.

Plasma are also formed in glass bulbs to produce light, usually in the form of UV and again a phospor is used to convert the UV light to visble light. These plasma bulbs are more efficient than incandesent bulbs. The main reason for this is that the incandesent bulb has a filament that is heated to several thousand degrees. When it is white hot we see the light. But we have to heat the filament so that creates a lot of heat energy and that is wasteful. With a plasma light we only heat the electrons and not the gas. As the electrons only make up a tiny mass compared to the mass of the filament then plasma lights are cheaper to run than filament. It is interesting that the father of plasma physics,Irving Langmuir, was also a developer of the incadesent bulb. So we see plasma are useful about the house even if plasma physicist like myself are not, and we have not got around to talk about all the things that are found in the house that are made by plasma. I think we will leave that for another day.

An exciting new concept is using plasma to sterilise skin: Plasma Sabre

and even brushing your teeth can do with a little help from plasma: Plasma Toothbrush