Researchers continued to look for and manufacture better piezo-electric materials. Ceramic materials are made piezo-electric by applying a very high polarizing voltage during its manufacturing. This technique has been found to work effectively on polyvinylidine fluoride (PVDF), a plastic polymer.
PVDF is the material in piezo-electric film. The high poling voltage polarizes and aligns the dipole molecules, which the PVDF material is stretched, see Figure 5. This molecular alignment creates the piezo-electric effect.
The PVDF piezoelectric material is a relatively new class of piezo-electric sensors. The PVDF material is a thin plastic polymer sheet that has a thin electrically conductive nickel copper alloy deposited on each side. This material is called piezo film. The material resembles aluminum foil, with the exception that it is more resilient, (doesn't crinkle as easily).
To use piezo film one makes an electrical connection to the electrically conductive coating on each side of the PVDF material. Most of the piezo-film sensors have wire connections. If one needs to attach electrical connections to raw piezo film this is accomplished using either copper tape or a conductive epoxy. Soldering directly to the film is not possible because the heat would destroy the underlying plastic PVDF material.