Multi-Layered Crack-Like Flexible Strain Sensor with Gradient Concentration Structure Based on Mxene-Ta-Pva

This study presents an innovative flexible strain sensor with high sensitivity, robust mechanical properties and rapid response through the novel design of a Janus gradient concentration structure combined with laser-thermocompression synergistic processing. The sensor employs MXene as the conductive unit, with polyvinyl alcohol (PVA) and tannic acid (TA) serving as the flexible substrate and interfacial reinforcement agent, respectively, achieving high sensitivity through gradient concentration distribution. Laser etching pre-engineered periodic primary cracks in the high-concentration MXene layer, while thermocompression induced the formation of a multi-level secondary crack network within the gradient layers, establishing strain-sensitive quantum tunneling conduction pathways. Experimental results demonstrated that the sensor exhibits an exceptionally high gauge factor (GF) along with ultra-fast response time. Mechanistic analysis revealed that the gradient structure synergistically enhances sensitivity through strain amplification effects and hierarchical crack propagation mechanisms. Simultaneously, the TA-mediated interfacial hydrogen-bond network coupled with the elastic recovery characteristics of PVA collectively ensures mechanical durability. This sensor demonstrates precise monitoring capabilities for human joint movements and pulse waveforms, providing a high-performance sensing solution for wearable electronics and soft robotics.