Self-healable bilayer film with ion accumulation interface for high-performance piezoionic tactile sensor

Abstract

Piezoionic materials have garnered significant attention for their unique ability to convert mechanical stress into ionic currents, providing innovative avenues for energy harvesting, sensing, and actuation. However, because of their low output signals and slow response time, they have limitations for practical applications. We report herein the development of bilayer-structured piezoionic materials with significantly enhanced output signal and response time. The material design is based on the bilayer structure of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) elastomer and the 1-Ethyl- 3-methylimidazolium bis(trifluoromethylsulfonyl) (EMIM TFSI) ionic liquid. This not only harnesses an ion accumulation interface, leading to amplified piezoionic output signals and enhanced response times, but also exhibits a unique ion-dipole interactive self-healing property. Our piezoionic sensor exhibits an output signal of 95 mV and a recovery time of 30 ms, along with a self-healing efficiency of ~100% under mild heating. Furthermore, capable of discerning both static and dynamic force stimuli, including directionality such as bending and vibrations, the sensor shows high durability across 1400 cycles of repetitive deformation. The practicality of our sensor is exemplified through its successful application in a braille reader device, paving the way for its integration into various soft and self- powered iontronic technologies that demand high sensitivity, rapid response, and self-sustainability.