Applications of flexible polyimide: barrier material, sensor material, and functional material

Polyimide (PI), as an advanced polymer material, possesses the intrinsic merits of excellent resistance to extreme temperatures, good dielectric properties, flame resistance, strong processibility, biocompatibility, and flexibility. The outstanding performances of flexible PI have led to a wide range of applications in aerospace, medical, intelligent electronic devices, energy storage devices, and more. Notably, due to the swift progress of various flexible and soft devices, flexible PI has become ubiquitous in the form of thin films, fibers, and foam and gradually plays an indispensable role in all sorts of those devices. This review mainly focuses on the current advances in the usage of flexible PI for barrier, sensor, and functional purposes. Firstly, the key features of various methods for synthesizing and processing PI, as well as the relationship with their respective applications, are summarized. Secondly, to give readers a comprehensive view of the various applications of flexible PI materials, the applications are broken down into three categories: flexible barrier applications, flexible sensing applications, and flexible function applications, and the current research of each application is introduced in detail. Finally, a summary of the challenges and possible solutions in some flexible applications is present.