Fabrication of poly (vinylidene fluoride) films by ultrasonic spray coating; uniformity and piezoelectric properties.

[Display omitted] • Ultrasonic spray coating system is used for fabrication of pure PVDF films with high piezoelectric coefficient (d 33 = 48 pm/V). • Highly crystalline (56%) PVDF films with predominant β phase for flexible and transparent engineering devices are achieved without post processing. • Uniformity and roughness (<50 nm) of the PVDF films strongly affects their piezoelectric properties. • We proved that the ultrasonic spray coating method is capable of producing large-scale, low-cost PVDF films in a single step. Piezoelectric Poly (vinylidene fluoride) (PVDF) films with high flexibility are a suitable and promising replacement for rigid ceramic piezoelectric materials. However, for this purpose, enhancing piezoelectric properties and adopting an industrial fabrication method are of great importance. In this study, 5–9 µm thick PVDF films were fabricated by a nozzle-less ultrasonic spray coating (USC) system, followed by an annealing process at 100 °C. By applying proper spraying parameters, we could obtain highly uniform films with large d 33 values (48 pm/V) and 56% crystallinity. Results show that the uniformity of the films plays an important role in the final piezoelectric properties. Thus, ultrasonic spray coating method can be used for fabrication of large-scale piezoelectric films with no need for poling or stretching processes. [ABSTRACT FROM AUTHOR]