Flexible Omnidirectional Strain Sensor Based on Ag Nanowire–Graphene–CNT Pattern with Equilateral Triangular Symmetry

Intelligent devices are rapidly evolving from single-function perception to multidimensional, networked sensing systems that mimic biological sensory capabilities. A critical requirement for such systems is the ability to monitor deformed surfaces over multidirections. However, most existing flexible sensors are typically limited to unidirectional strain detection under quasi-static conditions. Here, we developed an orientation-sensitive flexible strain sensor featuring an equilateral triangular silver nanowire pattern integrated with graphene/carbon nanotube electrodes. This design enables simultaneous acquisition of both the strain magnitude and direction on deformable surfaces. The sensor achieves an exceptionally low strain detection limit of 0.005%, a fast response time of 8.4 ms, cyclic stability exceeding 9000 cycles, and high angular resolution. Devices incorporating this sensor can conveniently capture multidirectional strain distributions during human joint motion and physiological activities and also dynamically record microstrains in metal fatigue testing at frequencies up to 35 Hz.