The big application for electrets right now is N95 masks. One of the inner layers is an electret. It will attract and hold particles smaller than the holes in the mesh. It doesn't take much of a static charge, because the particles only have to be pulled a few microns to be caught.
This is the huge difference between N95 masks and the cheapies.
I imagine it's more that it's a cheap way of achieving the effectiveness, vs. a (hypothetical/possibly extant, no idea) that doesn't use one.
'N95' is just a rating (roughly the same as 'FFP2' in Europe) concerning the rate of filtration.
Yes, it 'works as a protection from the outside', they block those particles they are rated to protect, which (by diameter of particle) includes the coronavirus.
Scarves and pieces of generic cloth or polyester sold as 'coronavirus mask' obviously do also protect from the outside, they're not somehow directional, it's just that they aren't particularly effective at relevant particle sizes, to put it in the extreme: they'll catch your sneezes. Of course they'll catch others' sneezes too, but usually people don't sneeze on your face, so it gets talked about as inside/outside as though direction matters.
> However, when an electret is moved with respect to a magnetic pole, a force is felt which acts perpendicular to the magnetic field, pushing the electret along a path 90 degrees to the expected direction of "push" as would be felt with another magnet.
The heck?? Why was I not exposed to this as a kid? (After searching awhile) Why does nobody make these for sale?
You probably have heard it before, you just need to connect it to the physics terminology. The Lorentz force law says that a charged particle moving in a magnetic field experienced a force given by the cross product of the velocity and the magnetic field:
I'm well familiar with the Lorentz force! Did homework finding paths charged particles take through fields and everything. What's novel to me (if obvious in retrospect) is that a nontrivial electric charge/potential can be frozen within a chunk of dielectric. This is as fundamental as magnetism, and I'm somewhat buffaloed by the fact that electrets aren't more commonplace novelty items.
«Historically, electrets were made by first melting a suitable dielectric material such as a polymer or wax that contains polar molecules, and then allowing it to re-solidify in a powerful electrostatic field. The polar molecules of the dielectric align themselves to the direction of the electrostatic field, producing a dipole electret with a permanent electrostatic bias.»
This is a short video showing a) how to make one b) the kinds of voltages /charge it can store as well as c) make a device to test it.
I found it pretty cool.
This is the huge difference between N95 masks and the cheapies.