>>403779768
You can use contact senders and receivers and measure the proximity to get a 0-1 float, which you can use to drive some blending parameter on your material. https://docs.vrchat.com/docs/contacts#receiver
Just position the contacts such that they become further away when unbent, and get close together when bent, and mess with it until you get an effect that you like.

I did something similar a while ago, didn't end up using it because the wrinkle shading I made was mediocre but the concept works. pic related.