The Water Electret

By Mike Johnston

Copyright 2003

An Electret is a substance which possesses a permanent electrical charge (potential difference). Much in the same way that a permanent magnet retains a magnetic charge indefinitely. Like the permanent magnet, the charge of the electret is a static one. In both cases the resulting charges are thought to be produced by an outside force causing the molecules of the substance to line up in a certain way. This alignment allows the energy aspects (whether magnetic or electric) of the individual atoms/molecules within the material to join together and, by doing so, produce a stronger field throughout/around the substance.

The most common permanent magnets today are made of iron or ceramics. Most electrets are made of plastics. The way that electrets are made is to melt the plastics. Then, when they are in a liquid state, to expose them to an electrical field. This causes the polar molecules within the plastic to orient themselves (“line up”), end for end along the electrostatic lines of force provided by the external field so that the positively charged pole of one molecule faces the negatively charged pole of the next and so on throughout the material.

The next step is to cool the plastic back into it's solid form while maintaining the electrostatic field as it cools. Once the plastic is solid again the external field can be removed and the plastic molecules, now within the more rigid confines of a solid structure, retain their end for end orientation and so a permanent electrostatic potential difference is thereby created between opposite sides of the material.

Please note that, under normal conditions, plastic is considered to be an electrical insulator. By this process though that insulator has become an electrically charged substance. Also note that the energy of the electrical field that was necessary to create the electret is not being somehow “stored” in the electret like the charging energy is stored in a battery. Instead, it is the electrical charges of the molecules of the substance themselves which provide and maintain the resulting charge.

An analogy would be the directing signs on a freeway. The signs get all of the vehicles on the road lined up and moving in the proper direction, in the proper lane and at the correct speed (for the most part). But the signs have nothing to do with the energy that is necessary to power the vehicles or to keep them moving once they are past the sign.

Considering these facts it soon becomes obvious that it would be not only possible but relatively easy to create an electret using water instead of plastic as the working substance. True the “manufacturing” process would have to be modified just a bit but the resulting process is simple enough that it will be a fun project for science fairs (with proper adult supervision).

Let's look at how we might create such a water electret. Water (H2O), is a tri-polar molecule. It has two positively charged poles (the hydrogen atoms), and one negatively charged pole (the oxygen atom). In a container of water these molecules do form various structures with each other based on the attraction of oppositely charged poles of adjacent molecules. The overall charge of the liquid is neutral though due to the somewhat random orientations of these structures in relation to each other.

Just like plastic water is considered to be an insulator. This is despite the fact that a tiny percentage of water molecules are always disassociated into H+ and OH- ions which also classifies water as an extremely weak electrolyte.

Since water molecules are electrically polar they will orient themselves into an external electrical field just like the plastic molecules in our previous example of a liquefied plastic. In that situation water molecules form “chains” along the electrostatic lines of force which pass through the liquid. The are lined up end to end, positive pole to negative pole. So both water and plastics are dielectrics which can be used to fill the space between the plates of a capacitor.

For the experimental setup I would construct a container made of clear plastic or perhaps a piece of PVC pipe, with two electrodes/ends made from a suitable metal, such as stainless. The metal would be glued to the plastic with some acceptable material such as silicon caulk. Once the cell is built it would be connected to an external DC power source such as a 12 volt battery. The higher the voltage here the better as long as there is no dielectric breakdown. The plates should be as close together as is practical as the less distance between them the stronger the electrostatic field will be and it is this field which aligns the water molecules.

Once the power source is turned on and the water molecules have oriented themselves into electrically charged chains we must allow the water to cool into it's solid form (ice) while keeping the electrical field in place as it solidifies. This could be accomplished by placing the unit in a freezer (with the power source connected).When the ice has totally formed the external field can be removed. The result should be a water electret with a measurable, permanent, electrical potential difference between the two sides of the ice which were oriented toward the opposite poles of charge provided by the external field. This potential difference being created by the opposite charges of the two ends of the water molecules lining up between the electrodes so that their negative sides face one electrode and their positive sides face the other, not by the external power source.

The intensity of the electrostatic field required to accomplish this effect remains to be determined by experimentation. It does appear however that this is likely to work as predicted here. The molecules within the cell will undoubtedly line up along the electrostatic lines of force just as any other dielectric does in a capacitor. The only potential problem will be as water freezes it goes into it's ice phase which is more of a crystal lattice. However, as long as this lattice lines up with the field as it freezes then it should work. I will update this paper as the necessary experiments are carried out. Feel free to experiment with this concept as you will just be kind enough to credit me with the idea.