These are called electrets. Tiny dipoles with positive and negative ends.
N95s only, not medical/surgical
Evidence on silk didn't pass muster and that's why we don't include it.
Here's an evidence based summary on materials for cloth masks⬇️
https://maskevidence.org/summary-of-advice
And here's our paper on cotton⬇️
That is the sweetest & most generous response I've ever had on either platform🙂❤️