Flexible Piezoelectric Papers Fabricated Using Amine-ModifiedCellulose Nanofibers and Boron Nitride Nanotubes Nanocomposites

In recent years, poly(vinylidene fluoride) (PVDF), widely used in piezoelectric applications, has been associated with health and environmental concerns due to issues regarding per- and polyfluoroalkyl substances (PFASs). There is an urgent need to find flexible piezoelectric materials. This study introduces a promising solution by developing flexible composite papers from boron nitride nanotubes (BNNTs) and cellulose nanofiber (CNF). CNF was modified with amine groups via ultrasonication and then combined with BNNT to form a flexible composite paper with exceptional thermal, mechanical, and piezoelectric properties. Notably, the paper demonstrated a 220% increase in thermal conductivity at 10 wt % BNNT compared to raw CNF paper and a d₃₃ piezoelectric response of −11.2 pC/N without a high-voltage poling process or mechanical stretching. BNNT-CNF composite paper provides a robust platform for advancing future energy technologies, paving the way for replacing PVDF in various flexible electronic and piezoelectric applications.