electrets and stupidity

So it dawned on me several weeks back that electrets might be a crucial component of my big project which I'm not ready to detail yet. For those of you that don't know, an electret is a dielectric piece of material with either a permanent electrical charge or one with its dipoles arranged in an order that reinforces its electric field similar to how a permanent magnet does with a magnetic field. Historically, the most common use for electrets was for a type of condenser microphone, where one of the plates is made from this material. Another example is adhesive-free graphic signage films like ClingZ. Now, its biggest, and perhaps most important use is in filtration products, such as the N95 face masks we've become so familiar with as of late.

So as I stated, there's two types of electrets: those that have their dipoles aligned, and those that have additional charges basically embedded in the material. The first is usually made by curing the material between two plates at a high electric potential difference. This aligns the dipoles, and once cured, get locked in place. The other method, in its simplest form, places the dielectric material between a conductive surface at ground potential and an electrode at a high positive or negative voltage depending on the type of charge you want you electret to have. The electrode is chosen so that it's prone to corona discharge, ionizing the air, and accelerating it into the dielectric. A newer method is the triode style, where like its namesake vacuum tube, places a "grid" between the dielectric and the discharge electrode. Presumably there's a whole bunch of variations of this method, but they share the key similarities.

At first, I was looking to purchase some bulk electret material, but all I could find was the ClingZ sheets. Once I realized that making my own was likely quite doable using the corona discharge method, I started leaning towards that, particularly since I could choose not only the type of charge, but also the field strength. What really sealed the deal was that by using a motorized drum as the ground plane, I could potentially create electrets with charge gradients; something that I don't think has ever been done intentionally, but could prove extremely useful in my project.

The next several blog posts will detail the work that is going into the project. Needless to say, it started out very hack-y. It has progressively gotten less so, but some stupid decisions were made early on that got cemented into some of the hardware, which should have been avoided with a bit more forethought.