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.
Anisotropic hydrogels are produced, by magnetic alignment of magnetically sensitized nanoclays followed by polymerization of the hydrogel to freeze the developed oriented structure.
Despite extensive advances in the use of piezoelectric materials in flexible electronics, they have numerous shortcomings, including low efficiency, limited flexibility, and lack of transparency. Additionally, the production of these materials is often limited to small batch processes which are difficult to scale up for mass production. A novel method to produce ultrasensitive, high performance, flexible, and transparent piezoelectric materials where both lead zirconate titanate nanoparticles, and graphene nanoplatelets are aligned together in polydimethylsiloxane under an AC electric field in the thickness (“Z”) direction, is reported here for the first time. The electric field alignment improves the piezoelectric response along with transparency and also reduces the amount of filler required to achieve outstanding piezoelectric properties. The resulting ultrasensitive piezoelectric film is able to sense the pressure of a bird feather (1.4 mg) dropped from a certain distance, whereas at the touch of a fingertip, it can generate up to 8.2 V signal. Moreover, the mass production compatibility of the system is also demonstrated by producing a 3 m long and 15 cm wide large‐area sample via a novel 44′ long roll‐to‐roll manufacturing line which is designed and developed by the group.
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