**2.2. Polarization**

PVDF is polymorphic and has a crystalline phase (ß-phase). The ß-phase is the most relevant phase for practical ferroelectric, piezoelectric, and pyroelectric applications. Several methods are commonly used in order to achieve this phase, such as stretching the material, applying a voltage of at least 0.5 MV/cm, or using plasma or corona poling [7].

The ear prosthesis made of PVDF was poled by corona poling, where a high voltage (15 kV) was applied between a needle and a plate, situated 1 cm apart. PVDF prosthesis was placed over the plate, so the molecules of this polymer are aligned [7, 10].
