Piezoelectric Polymers and Their Applications

The science and technology of piezoelectric polymers has long been dominated by ferroelectric polymers from the polyvinylidene fluoride (PVDF) family. The piezoelectricity in this polymer class arises from the strong molecular dipoles within the polymer chain and from the resulting change of the dipole density upon application of a mechanical stimulus. Ferroelectric polymers show moderate piezoelectric coefficients (d ₃₃ around 20–30 pC/N) in comparison to ceramic piezoelectrics, with an acoustic impedance comparable to that of water and other liquids. The thermal stability of the piezoelectric effect is limited to below 100°C [1]. Applications of ferroelectric polymers emerged in many niches [2], examples are hydrophones [3] and clamp-on transducers [4] used as pressure sensor for diesel injection lines, with selling numbers over 50 million pieces per year, as well as piezoelectric ignition systems [5] for measuring the mechanical and physical state of matter under shock loading. Printable polymer ceramic composites [6] and nanocomposites [7] further enlarge the material basis available to application engineers.