Breathable and Large Curved Area Perceptible Flexible PiezoResistive Sensors Fabricated withConductive Nanofiber Assemblies

Abstract：The rapid developmentof wearable electronics, humanoid robots and artificial intelligencerequire sensorsto sensitively and stably percept external stress variations in large areas oronthree-dimensional(3D) irregularly shaped surfaces while it possesses comfort at the same time.Prior to all, the flexibility and3D compliance of sensors, and the fitting state of the interfacebetween the sensor and the objectare of great significance to the sensing accuracy and reliability.The ordered or randomly stackingand entangling of flexible and electrically conductive fibermaterials can form a highly porousand mechanically stable fiber assembly. The changes inexternal stress can lead to the airtrapped in the fiber assembly to flow in and out rapidly andrepeatedly, as well as thereversible mechanical deformation of fiber materials. Correspondingly, the contact areas betweenelectrically conductive fibers in the fiber assembly reversibly changed,which makes the conductive andflexible fiber assembly be an ideal candidate for piezo-resistivesensing material. It can be furtherexpected that the statistical stability of contact points betweenconductive fibers under the stressmay significantly increase with the decrease in fiber diameters. Herein, a new method to make aflexible piezo-resistive sensor with conductive and porous fiberassembly was proposed. Anultra-sensitive piezo-resistive material was facilely prepared byfabricating conductive Poly (vinylalcohol-co-ethylene) (EVOH) nanofiber assemblies. Thesensing performance of thepiezoresistive sensor were optimized by regulating the nanofibermorphology, electrical conductivityand mechanical properties. The flexible piezo-resistive sensorexhibited a sensitivity of 2.79 kPa-1,a response time of 3 ms and a recovery time of 10 ms. Thesensing performance at differentworking frequencies was stable and durable within 4500 timescycling test. The flexible sensorshowed good pressure sensing accuracy and reliability whilebeing used on irregular surfacesand was further applied in the static monitoring of large-area spatial pressure distribution andthe wearable intelligent interactive device, demonstrating greatapplication potential.

Zhong Weibing, et al. Breathable and Large Curved Area Perceptible Flexible PiezoresistiveSensors Fabricated with Conductive Nanofiber Assemblies. ACS AppliedMaterials & Interfaces, 2020, 12, 37764-37773.