Unexpected piezoelectric properties of electrospun polyimide nanofibers for application in an extreme environment

Developing a piezoelectric polymer with high-temperature resistance is crucial for fabricating flexible piezoelectric sensors that can be used under extreme conditions. Herein, we for the first time found the piezoelectric properties of polyimide (PI) nanofibers and further enhanced their output voltage characteristics by introducing a fluorine-containing hexafluorodianhydride (6FDA) unit into the PI nanofibrous matrix. The as-fabricated sensor can produce a stable piezoelectric output of 10 V with a 478.72 mV N−1 sensitivity. The response and recovery times are 15 ms, respectively, and the output can remain stable after 10,000 cycles at 15 Hz/10 N, demonstrating excellent durability. Meanwhile, the 10–30 V piezoelectric output signals generated by different actions can be accurately identified for wearable applications. Furthermore, it is found that fluorinated polyimide (FPI) prepared by electrospinning can maintain structural stability before 500 °C, and its thermal decomposition temperature is above 550 °C. Moreover, the surface morphology with high porosity and the low surface energy of F atoms endow the nanofiber film with excellent superhydrophobic properties with a water contact angle of 139.6°. This work presents PI nanofibers with high-temperature resistance and outstanding piezoelectric properties, laying a potential foundation for their application in wearable and flexible electronic devices that can be used in extreme environments.