Ultrasensitive\nand Stretchable Strain Sensors Based\non Mazelike Vertical Graphene Network

Abstract

Here, we report a\nnew type of strain sensors consisting of vertical\ngraphene nanosheets (VGNs) with mazelike network, sandwiched between\npoly­(dimethylsiloxane) (PDMS) substrates. The new sensors outperform\nmost graphene thin-film-based sensors reported previously and show\nan outstanding combination of high stretchability of ∼120%,\nexcellent linearity over the entire detection range, and high sensitivity\nwith a gauge factor of ∼32.6. The sensitivity can be tuned\nby controlling the thickness of VGNs, with sensors consisting of thicker\nVGNs showing higher sensitivity but slightly lower stretchability\n(the maximum gauge factor is ∼88.4 with a maximum detection\nstrain of ∼55%). Detailed microscopic examinations reveal that\nthe ultrahigh sensitivity stems from the formation of microcracks\ninitiated in the buffer layer. These microcracks are bridged by strings\nof graphene/PDMS, enabling the conductive network to continue to function\nup to a strain level significantly higher than that of previously\nreported graphene thin-film-based sensors. Furthermore, the present\nsensors have been found to be insensitive to temperatures and various\nliquids, including water and 0.1 mol L^–1 sodium\nchloride solution (similar to the sweat on human skin). Demonstrations\nare presented to highlight the new sensors’ potential as wearable\ndevices for human motion detection and pressure distribution measurement.