Enhancing the sensitivity of graphene/polyurethane nanocomposite flexible piezo-resistive pressure sensors with magnetite nano-spacers

A robust piezo-resistive nanocomposite flexible sensor has been developed using an innovative combination of materials, i.e., magnetite-decorated graphene/poly(ionic liquid) compatibilized poly(-urethane) (TPU/Fe3O4@RGO-PIL). The transducer has been fabricated by spray layer by layer (sLbL) to structure an original three-dimensional architecture in which: reduced graphene oxide (RGO) platelets are used to build the conducting network, PIL stabilizes this percolated assembly, Fe3O4 NP act as nanospacers between platelets to prevent their stacking and facilitate their switching, and TPU matrix brings cohesion and flexibility to the whole assembly. This strategy results in highly sensitive TPU/Fe3O4@RGO-PIL flexible nanocomposite sensors (high gauge factor in pure compression up to 6.2, exceptionally low threshold pressure 0.5 kPa, Negative Pressure Coefficient), yielding a linear response in a large range of pressures (10-200 kPa), with robust and reproducible piezo-resistive properties (weak hysteresis upon loading unloading cycling, stability of signals up to 100 000 cycles, with 2 ms dephasing). These performances are promising for a variety of applications in flexible and wearable electronics, such as tactile sensors, sensing skins and compressive strain sensors. (C) 2016 Elsevier Ltd. All rights reserved.