Shape key on particle collision?

Wasn’t sure if I should post this here or in the particles section.

Anyway, I have a lot of particle objects being fired at random from an emitter, where these then stick to a surface (forcefield with 100% friction/damping/force absorbtion). I want these to then change shape in a specific fashion using shape keys.

Is it possible to make the particles “aware” of when they hit the surface and then (and only then) activate a shape key transition?

Or is there any other way to do this without having to manually animate everything?