Transfer-Free PZT Thin Films for Flexible Nanogenerators Derived from a Single-Step Modified Sol-Gel Process on 2D Mica

Piezoelectric materials enable emerging self-powered wearable and implantable devices. The sol-gel technology with the lowest cost for large-scale production has shown its potential for producing high-quality PZT thin films. However, fabricating PZT films with a sufficient thickness for different application scenarios requires a long and repeated coating and heat-treatment process. The traditional solution-based method usually requires at least 20 coating cycles to fabricate 2 μm-thick PZT thin films. To save cost and improve fabrication efficiency, we develop a simplified thin-film fabrication method assisted by PZT powder. The new method can fabricate 2 μm-thick PZT films in a single step, one spin coating and annealing. Experiments indicate that the powder-based PZT thin films have porous structures and outstanding piezoelectric performances. The measured d33 of the powder-based PZT thin film is 47 pm/V. Both solution-based and powder-based PZT thin films show high flexibility and good fatigue resistance. Furthermore, we explore 2D mica as the substrate and achieve the transfer-free fabrication of flexible PZT thin-film nanogenerators that effectively simplify the complicated physical or chemical thin-film lift-off processes. The nanogenerator prototypes demonstrate the capability of accurately monitoring dynamic responses of flexible and soft human tissues.