Basically it is a plastic that is both piezoelectric and pyroelectric. That means that it will build up electric fields when you squeeze/bend it as well as when you heat it.
In this interesting presentation, they demonstrate how a small sheet of this plastic can be used in sensors to detect both movement and heat.
The approach I would like to test is to simply cover the robot in a sheet of crumpled PVDF connected to an array of electrical probes, and then simply empirically collect data from the probes as the robot changes pose. The data can then be fed into a learning algorithm of some sort to detect abnormalities from the expected pose an the real pose.
I also have another use for this material in the robot, but the ideas are too far off to put on this blog just yet. Maybe in a later post :-)