- I want to stick them onto a plastic foil and see weather I can bend the foil. Sort of like a wing. How can I do that?
You probably can't - but it wouldn't hurt to try. From what I have read, piezo disks only "flex" in the sub-millimeter (very "sub") range. You could potentially try to stack them (epoxy the disks together?) to potentially gain more working "length"...
There do exist piezo actuators that "flex" more - and are used for short distance mechanical positioning - such as what this company supplies:
They aren't cheap!