Ultrasensitive, flexible, and low-cost nanoporous piezoresistive composites for tactile pressure sensing.

Highly sensitive flexible tactile sensors are of continuing interest for various applications including wearable devices, human-machine interface systems, and internet of things. Current technologies for high sensitivity piezoresistive sensors rely on costly materials and/or fabrication methods such as graphene-based and micro-structured composites limiting accessibility and scalability. Here, we report a facile sacrificial casting-etching method to synthesize nanoporous carbon nanotube/polymer composites for ultra-sensitive and low-cost piezoresistive pressure sensors. Our synthesis method overcomes the limitations of the traditional solution-dip-coating method for adhering nanoscale conductive materials to the nanoscale porous surface. Importantly, we show ultra-high sensitivity with a strain gauge factor over 300, which is ∼50 times higher than that of traditional CNT-based piezoresistive sensors and ∼10 times higher than that of most of the graphene-based ones. For practical tactile sensing applications, we demonstrate that the sensors can detect both gentle pressures (1 Pa-1 kPa) and low pressures (1 kPa-25 kPa) with a fraction of the cost. Our nanoporous polymer composite could contribute to expanding the scope of using nanocomposites for applications including subtle locomotion sensing, interactive human-machine interface systems, and internet of things from its easy tunability for sensing diverse range of tactile signals.