Nonequilibrium Triboelectric Response of Bacterial Cellulose/Titanate Nanotube Composites under Hot-to-Cold and Cold-to-Hot Thermal Transients

Cellulose-based flexible electronic materials are commonly studied under near-equilibrium thermal and hydration conditions, whereas their electrical behavior under rapid thermal perturbation remains largely unexplored. Herein, we investigate the triboelectric response of bacterial cellulose/titanate nanotube composites (BC/TNT, 3 and 10 wt % TNT) under rapid hot-to-cold (H → C) and cold-to-hot (C → H) thermal transients (∼12–24 °C min–1). Open-circuit voltage (VOC) and short-circuit current (ISC) of the composites were monitored, enabling direct observation of dynamically evolving electrical behavior. Compared to pristine BC, the composites exhibit pronounced transient-dependent triboelectric responses during both processes, with the outputs increasing with temperature and TNT loading. Infrared thermography reveals that TNT incorporation promotes broader and more continuous thermal redistribution, consistent with enhanced lateral heat transfer. Under externally imposed temperature gradients, the BC/10TNT composite develops ribbon-like thermal fronts with effective positive Seebeck coefficients of ∼1.5–4.6 mV K–1. Finite element simulations reproduce the experimentally observed voltage evolution and spatially localized potential distributions. The findings are discussed in terms of nonequilibrium competition between triboelectric charge generation and hydration-dependent charge relaxation, with spatially evolving temperature gradients contributing to transient electrical response. Our results may provide insights for future motion/thermal sensing systems and dynamically adaptive triboelectric devices.