Roll-to-Roll Production of Novel Large-Area Piezoelectric Films for Transparent, Flexible, and Wearable Fabric Loudspeakers

High-performance flexible loudspeakers have the potential to revolutionize the future of flexible/wearable electronics by providing this long-sought function. Here, a novel method is developed to produce large-area, flexible, and transparent piezoelectric loudspeakers, where both piezoelectric lead zirconate titanate (PZT) nanoparticles and graphene nanoplatelets (GNPs) are simultaneously aligned in the thickness direction forming dense nanocolumn forests. The preferential alignment of the particles not only reduces filler concentration and improves the piezoelectric performance, but also provides transparency to the film by enabling light to travel with little scattering or absorption in the thickness direction. Its potential applications, such as wearable and portable personal audio systems, along with a 9-ft-tall immersive walk-through soundscape structure, are also demonstrated. The performance and the directivity of each loudspeaker are characterized through sound pressure level (SPL) versus frequency measurements over human audio spectrum (20 Hz-20 kHz) in an anechoic chamber. Furthermore, scalability of this unique roll-to-roll process is demonstrated on a 44-ft-long custom designed roll-to-roll (R2R) manufacturing line that can produce these six-inch-wide multifunctional films continuously.