Wide Linear Range Strain Sensor Enabled by the Non‐Newtonian Fluid for Bio‐Signals Monitoring

Abstract

Wearable strain sensors with a wide linear range (i.e., sensors established on piezoresistive materials) are highly desirable in detection of human motion, as well as for the evaluation of physical rehabilitation. However, most piezoresistive devices possess poor linearity in the working range due to the exponential collapse of the solid conductive structures under high strain, thus limiting their batch applications. Herein, a strain sensor with a broad linear detection range by virtue of a non‐Newtonian fluid (NNF) is reported. Graphitized carbon black (GCB) is employed to create the conductive network and subsequently embedded in defatted cellulose nanofiber (CNF)‐insulating framework. After the GCB/CNF liquid is encapsulated into the elastic polymer, the conductivity shows excellent response to tensile strain (gauge factor = 5.47). The conductivity does not drop sharply under large deformation, and the device reveals a linear response in the whole sensing range up to 100%. The sensor, which exhibits a stable performance with excellent sensitivity, durability, and low hysteresis, is applicable for real‐time monitoring bio‐signals, including pulse, muscle, and joint movements. All these results inspire a simple but promising route to design high‐performance wearable devices.