Self‐Powered Flexible Dual‐Mode Humidity Sensor Enabled by Integrated TENG and Visualized Cellulose Nanocrystals

ABSTRACT Cholesteric liquid crystals are 1D photonic crystals with a helical structure that can selectively reflect light. In this study, we successfully fabricated color cholesteric liquid crystal films using cellulose nanocrystals (CNC) and citric acid (CA) through co‐assembly. Due to the reversible swelling and dehydration of its chiral structure, the CA/CNC composite film exhibits reversible structural color responses between green and dark red at relative humidity (RH) of 43%–97%. When used as the friction material for TENG, the CA/CNC composite film exhibits excellent triboelectric performance, with a response time of approximately 22 ms, open‐circuit voltage, short‐circuit current, charge density and power density of 187.17 V, 7.75 µA, 86.06 nC, and 1.21 W/m 2 , respectively. CA/CNC‐TENG functions not only as a power supply but also incorporates humidity sensing capabilities. When establishing sensing relationships between electrical signals and visual signal RGB values with humidity respectively, its minimum detection limits are 2.4% and 4.9% RH, respectively. Utilizing a convolutional neural network deep learning model to analyze electrical signal and visual signal RGB value data, the average recognition accuracy rates were 95.90% and 97.91% respectively. The integrated CA/CNC‐TENG color‐visualized humidity sensor may significantly promote the application of TENG in electronic detection devices and environmental monitoring fields.