MXene quantum dots regulated high performance PVA mechanoionic generators as self-powered sensors for handwriting recognition

Introduced MXene quantum dots (MQDs) as ion-selective fillers to PVA hydrogel created ion transport asymmetry through selective ion interactions. • MQDs–PVA mechanoionic generator achieved 5.5 mA current, 0.81 V voltage, and 0.937 W m −2 power density, well balanced and stable electrical performances. • A 4 × 4 self-powered pressure-sensing array integrated with temporal convolutional network enabled 96.68% handwriting recognition accuracy. Mechanoionic generators based on ionically conductive hydrogels have emerged as promising candidates for self-powered sensing applications, but with limited electrical performances due to insufficient ion-transport asymmetry. Herein, MXene quantum dots (MQDs) as ion-selective nanofillers are introduced into poly(vinyl alcohol) (PVA) hydrogel to regulate ion transport for mechanoionic performance enhancement. Owing to the hydrothermally prepared MQDs with abundant oxygen-containing functional groups, the nanoscaled particles are interacting with selected ions and tailoring steric hindrance to diffusion. The Density Functional Theory (DFT) studies reveal that the MQDs exhibit strong adsorption toward Li + but repulsive to Cl − , thereby amplifying the intrinsic diffusion difference between cations and anions under compressive strain. As the result, the MQDs-PVA mechanoionic generator offers short-circuit current of 5.5 mA, open-circuit voltage of 0.81 V, and maximum power density of 0.937 W m −2 , outperforming the MXene-based counterpart and the most reported piezoionic systems in literature. Furthermore, a 4 × 4 self-powered pressure-sensing array is constructed and integrated with a temporal convolutional network (TCN), which enables handwriting authentication at minimum sample rate. This study has paved the ways to build high performance mechanoionic generators for practical applications.