Highly Conductive Polydimethylsiloxane/Carbon Nanofiber Composites for Flexible Sensor Applications

A polydimethylsiloxane (PDMS)/carbon nanofiber (CNF) nanocomposite with piezoresistive sensing function is presented. Excellent electrical conductivity is achieved by dispersing the CNFs into PDMS. A facile, low cost, and scalable fabrication procedure allows the sensors to be made in different shapes. The piezoresistive sensors show repeatable response up to 30% tensile strain. In addition, the characterization of sensing mechanism using an in situ mechanical testing system within a scanning electron microscope reveals the reorganization of CNF network by varying fiber alignment and interfiber distance in the nanocomposites under tensile load. To validate the wearable sensing capability, nanocomposite straps are employed to monitor the finger motions under various bending speed and holding time. Two different shapes of compressive sensors, including cylinder and truncated cone, are tested in compression strain as low as 3%, with gauge factors of 18.3 and 6.3, respectively. In addition, the sensing capability is independent of the applied strain rates and is highly repeatable in 1000 cycles under compression. Finally, the developed nanocomposites are made into sensor arrays for pressure sensing ranging from 35 to 690 kPa. The versatility and ease of fabrication of the reported nanocomposites can bridge the current challenge between performance and applicability of flexible sensors.