Wearable\nPressure Sensors with Capacitive Response\nover a Wide Dynamic Range

Abstract

At\npresent, there are mainly two types of capacitive pressure sensors\nbased on ordinary capacitance and electrical double layer (EDL) capacitance.\nHowever, few researchers have combined these two types of capacitors\nin pressure sensing to improve the dynamic range of a sensor under\npressure. Here, we fabricated a capacitive pressure sensor with an\nasymmetric structure based on poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) using a simple electrospinning process. A layer\nof mixed ionic nanofiber membrane and a layer of pure nanofiber membrane\nwere stacked and used as the dielectric layer of the sensor. Due to\nthe porous structure and non-stickiness of the pure nanofiber membrane,\nit can be penetrated by the mixed ionic nanofiber membrane under pressure,\nrealizing the reversible conversion from ordinary capacitance to EDL\ncapacitance, thereby achieving a great change in the capacitance value.\nThe sensitivities of the sensor are 55.66 and 24.72 kPa^–1 in the pressure ranges of 0–31.11 and 31.11–66.67\nkPa, respectively, with good cycle stability, fast loading–unloading\nresponse time, and an ultra-low pressure detection limit as low as\n0.087 Pa. Finally, this sensor was used for the detection of human\nphysiological signals, and the sensor would have potential applications\nin the fields of human tactile sensing systems, bionic robots, and\nwearable devices.