High sensitivity and wide sensing range graphene flexible strain sensors based on pre-stretching and layer-by-layer self-assembly

In recent years, the development of strain sensors exhibiting heightened sensitivity and an expansive sensing range has emerged as a challenging and pivotal focal point within contemporary research endeavors. The preparation of conductive layers with micro- and nanostructures is a critical trade-off between sensitivity and sensing strain range. This paper presented a novel method for preparing high-performance flexible strain sensors by developing a graphene oxide-based sensor through the integration of layer-by-layer (LbL) self-assembly and pre-stretching techniques. The high sensitivity is due to the cracks created in the conductive layer during prestretching, and the wide sensing range is due to the folds formed in the conductive layer as a result of the release of pre-stretching. Additionally, the controllability of LbL deposition enables precise timing for introducing pre-stretching, optimizing the preparation of flexible strain sensors. The optimized pre-stretched GO (PSGO) sensor features a wide sensing range (0-150 %), high sensitivity (GF=5.9), fast response (192 ms) and good cyclic stability (1000 cycles). Notably, it exhibited a unique signal response when monitoring human motion with varying amplitudes and motions, highlighting its potential applications in smart devices, e-skins, and wearable medical monitors.