Hybrid systems of three-dimensional carbon nanostructures with low dimensional fillers for piezoresistive sensors

As an alternative of single filler system, hybrid fillers system is beneficial for the fabrication of elastomer-based piezoresistive strain sensors with high strain sensitivity for structural health monitoring and human motion detection. However, a comprehensive understanding for the effect of the secondary filler dimensionality on piezoresistive strain sensor sensitivity by hybrid carbon nanofillers strategy is missing. Here, we report a comparative study about the effect of branched carbon nanostructures (CNS, three-dimensional, 3D) combined with carbon black (CB, 0D) or carbon nanotubes (CNT, 1D) on the piezoresistive behavior of thermoplastic polyurethane (TPU)-based composites. At either the same total filler content or similar electrical resistivity, using CNS-CB hybrid is more efficient than using CNS alone or CNS-CNT hybrid for improving piezoresistive sensitivity of the TPU composites. For instance, the composite 1.5CNS-1CB has a gauge factor (G(F)) of 21 and 99 at strain epsilon = 50 and 100%, respectively, while the composites 2.5CNS and 1.5CNS-1CNT have G(F) values of 4.3 and 9.1 at strain epsilon = 50% and 14 and 20 at strain epsilon = 100%, respectively. Besides, the TPU composite with CNS-CB shows a larger response to finger bending (50 degrees on an index finger) by comparison with that contains only CNS, indicating potential applications for human motion detection. This study introduces a facile way to fabricate strain-sensitive sensors aimed at strain of 50%-100%, strengthening understanding the selection of hybrid carbon nanofillers with different dimensionalities to optimize piezoresistive sensor design.