Stretchable and ultrasensitive strain sensor based on a bilayer wrinkle-microcracking mechanism

Abstract

As a fundamental component for human–machine interaction and human health monitoring, stretchable strain sensors suffer from an irreconcilable trade-off between sensitivity and stretchability. This severely limits their capability to detect both subtle and large deformations simultaneously. Here, a new class of strain sensors is proposed based on a hitherto unexploited strain-sensing bilayer consisting of a pre-wrinkled reduced graphene oxide layer and a highly susceptible layer of conformally deposited Ag nanoparticles. During straining, the pre-wrinkled interlayer guides preferential microcracking at the wavy troughs of the conformal Ag surface-layer, leading to effective integration of the irreconcilable sensitivity and stretchability. The obtained strain sensor not only shows high stretchability, but also owns unprecedented gauge factor (GF) both in subtle and large strain ranges (0–2%, GF: 420; 110–125%, GF: 1.1 × 109), ultralow strain detection limit (0.01%) and ultrafast response (0.13 ms). As demonstrated, the strain sensor has superior capabilities in diverse human motion detection and voice recognition over the whole audible frequency range (20–20000 Hz) with ultrahigh frequency resolution (0.5 Hz). It is expected that the novel wrinkle-directed dynamic patterning/structuring (e.g., microcracking in the current case) involved in the proposed bilayer design can be extended to fabricate a new generation of stretchable sensing devices with unprecedented capabilities.