looking for a way to make a variable capacitor

[ytrewq]

For my idea i need a fast changing variable capacitor.

Of course, a variable capacitor is easy and off the shelf. But i want it to change fast (>100Hz, but eventually >1000Hz. higher is better) and have a large capacity (at least 10nF, but later 1uF is better) and with a voltage of at least 100V (but later 500V). Of course, for the proof of concept i am working on the minimal values are sufficient.

Current ideas i had:
1. something like an electrostatic motor rotor like this: https://www.c-motive.com/tech . This is very good but very hard.
2. use a dielectric of which the permeability can change under pressure. Then change the pressure with an actuator. I do not know if there is such a material (e.g. kind of a piezo but then without the voltage effect)?
3. a condensor microfone setup: thin flexible plates close to each other with some gas (air) in between. Then change the distance using high pressure sound waves.

Any ideas are welcome!

Thanks