Wearable Energy Harvesting and Biomechanical Sensing Enabled by Ferroelectric Nematic Liquid Crystal-PVDF Nanofibrous Hybrid TENG

Ferroelectric nematic liquid crystals (FNLCs), a novel class of liquid crystals (LCs) discovered recently, stand out as a fascinating polar soft matterial that displays macroscopic orientational order, whilst also possessing spontaneous polarization dipoles. Taking advantage of this polar ordering, we incorporated a room-temperature FNLC into poly(vinylidene fluoride) (PVDF) fibrous matrix using the electrospping process, to achieve a flexible electroactive layer for a triboelectric nanogenerator (TENG). A spin-coated PEI/Nylon-6 layer was employed as the counter-electropositive layer. The FNLC incorporation at an optimum concentration induces strong interfacial polarization within the β-phase-rich PVDF matrix, enhancing the dielectric permittivity. The pristine PVDF/PA-6 TENG device (V_OC~220 V) under an impact frequency of ≈10 Hz and force 8 N delivers an output voltage of ~395V. Detailed characterization reveals the development of FNLC microdroplets within the PVDF fibrous network, acting as polarized domains, boosting local field coupling and interfacial charge trapping capability. The real-life application of the TENG assembly was shown when employed in a precise biomechanical sensing application; the composite demonstrates a highly reproducible electromechanical response to finger/arm/elbow bending-flexion. Thus, we have demonstrated for the first time that the FNLC order of an LC can be transduced for self-powered hybrid energy harvesting and sensing applications.