Flexible piezo-resistive strain sensors based on silver nanowires and graphene nanoplatelets reinforced polydimethylsiloxane for human motion detection

In this work, flexible sensors consisting of silver nanowires (Ag NWs), graphene nanoplatelets (GNP), and polydimethylsiloxane (PDMS) are fabricated using a straightforward, affordable, and simple solution processing technique. The performance of the flexible devices with structure Ag NWs/GNP/PDMS has been studied, in which Ag NWs/GNP-based ternary conductive hybrid nanocomposites are used as acting sensing layers. The diameter of Ag NWs and flake size of GNPs were determined to be 80-160 nm and 30-190 nm, respectively. The Raman peaks of Ag NWs within the composite are appeared at 392.08, 482.12, 543.7, 679.42 and 854.87 cm(-1). The peaks existing at 1317.68, 1565.36 and 2639.75 cm(-1) represent the D, G and 2D bands of GNP, respectively. The gauge factor is determined to be 865 within the strain range of 0-71 %. The response and recovery time of the fabricated sensor are calculated to be 101 and 110 ms, respectively. The sensor exhibits a minimum detectable limit of 0.8 %. The sensor shows a highly reproducible response for more than 1150 bending and stretching cycles suggesting long-term durability which may be attributed to the Ag NWs/GNPs conductive networks for significant strengthening the hybridisation with PDMS. Different human activities, viz. finger bending, stretching, mouse/mobile screen scrolling, swallowing through the throat and drinking are monitored by the fabricated Ag NWs/GNP/PDMS-based flexible strain sensor, indicating promising applications in wearable electronics.