Flexible high-temperature piezoelectric nanogenerators for dual-mode energy harvesting and safety monitoring in harsh environments

초록

With wearable electronics and self-powered sensing systems increasingly used in harsh, high-temperature environments, flexible piezoelectric nanogenerators (PENGs) with stable performance at elevated temperatures are becoming essential for reliable operation. Herein, we report a dual-mode PENG based on polyimide (PI) and dual-phase (tetragonal-rhombohedral) K-0.Na-5(0).5NbO3 (KNN) ceramic fillers. The coexistence of both crystal phases enables simultaneous activation of longitudinal (d(33)) and transverse (d(31)) piezoelectric modes, enhancing energy harvesting efficiency under multidirectional deformations. The optimized PI-20KNN composite exhibited excellent thermal stability (operational up to 150 degrees C), and at 110 degrees C it delivered a high open-circuit voltage (similar to 12 V), fast response time (similar to 82 ms), and long-term durability over 6000 cycles, outperforming most reported flexible PENGs. Notably, the device displayed a temperature-sensitive dual-peak output (similar to 70 degrees C and similar to 110 degrees C), tunable by KNN loading. This thermally adaptive behavior enables temperature-selective response and is leveraged to construct a self-powered fire alarm system with remote signal transmission. Additionally, the composite films demonstrated hydrophobic behavior (WCA > 90 degrees), making them suitable for use in humid environments. This work provides a scalable strategy to develop lead-free, thermally responsive, and dual-mode piezoelectric devices for wearable safety monitoring and intelligent energy systems.

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