Crack-Modulation Strategy Enabled Flexible Strain Sensor with Ultra-High Gauge Factor and Broad Strain Range for Wearable Health Monitoring

Flexible strain sensors capable of combining high sensitivity with a broad working range are highly desirable for wearable health monitoring and human–machine interfaces. However, conventional designs often suffer from a trade-off between these two key parameters. Inspired by the connectivity principle of ancient bamboo slips, this work presents a crack-modulation strategy for fabricating a highly sensitive and wide-range strain sensor. The device is constructed by sequentially depositing a nonstretchable silver electrode onto a thermoplastic polyurethane (TPU) fibrous mat via screen printing, followed by mechanical stretching to induce controlled microcracks. A second patterned stretchable silver electrode is then printed over the cracked layer to reconfigure the electrical pathways from parallel to perpendicular to the tensile direction. This design effectively “locks” the crack edges and reestablishes conductive routes during deformation, enabling simultaneous ultrahigh sensitivity (gauge factor >106) and a wide sensing range (>100%). The sensor also exhibits excellent stability, breathability, and skin compatibility, demonstrating great potential for detecting both subtle physiological signals and large joint motions in real-world wearable applications.