A flexible multifunctional triboelectric nanogenerator based on bio-inspired nanocellulose/tannic acid@MXene-composited hydrogel for human healthcare

MXene-composited conductive hydrogels have received extensive attention in flexible, portable and self-powered wearable electronics based on triboelectric nanogenerators (TENGs). Yet, the incompatibility of the MXene with hydrogel matrix due to easy oxidation and weak interactions with polymer chains weakens the performance of hydrogels. Herein, inspired by the structure of leaves, tannic acid (TA) with abundant catechol groups was introduced to encapsulate MXene and TEMPO-oxidized cellulose nanofibers (TOCNF) was intercalated to support the MXene nanosheets as leaf vein, forming a stable TOCNF/TA@MXene nano-motif with three-dimensional (3D) network. Benefiting from the addition of TOCNF, TOCNF/TA@MXene exhibited long-term stability (>10 days) in aqueous environment with the presence of oxidant. Therefore, the obtained TOCNF/TA@MXene-composited hydrogel (PCM) exhibited high stretchability (>800 %), reliable fatigue resistance and good adhesiveness, which can be served as electrodes of flexible TENGs. The formed PCM-TENG demonstrated flexibility and versatility, achieving an open-circuit voltage of 106 V, a short-circuit current of similar to 2 mu A and a transfer charge of similar to 31 nC even in a single-electrode mode. Besides, PCM-TENG showed enduring practicality and responsiveness as a self- powered sensor to detect human biomotions. PCM-TENG also presented desirable photothermal antibacterial capacity and cytocompatibility. All these properties endowed the PCM-TENG with great application potential in human healthcare.