Flexible strain sensors are promising for wearable devices. Crack-based sensors offer ultrahigh sensitivity, but large strains cause fractures. This work uses CNTs and AgNWs deposited on electrospun TPU fiber mats via vacuum-assisted filtration to create a microcrack structure. Prestretching allows a wide working range (0–171% strain), ultrahigh sensitivity (gauge factor of 691 within 0–102% strain, ~2 × 10<sup>4</sup> within 102–135% strain, and >11 × 10<sup>4</sup> within 135–171% strain), fast response time (~65 ms), small hysteresis, and superior durability (>2000 cycles). The distributed microcrack propagation based on the “island-bridge” structure enhances sensitivity. The sensor monitors vibration signals and human motions, showing potential for electronic skin and health monitoring.
