Nanoengineered highly sensitive and stable soft strain sensor built from cracked carbon nanotube network/composite bilayers

Sensitivity and stretchability are two key physical parameters for advanced piezoresistive sensors, especially for those that can be incorporated into clothing or attached directly on human body. Big challenge remains in achieving both in single device. Here, to obtain high strain sensitivity and wide measurement range simultaneously, a nano-engineered bilayer composed of cracked carbon nanotube (CNT) network and elastomer infiltrated CNT composite has been developed. This design takes advantage of the cracked CNT network layer which is able to provide the sensor with high resistance sensitivity (gauge factor between 8 and 207), wide strain measurement range (>50%) and good linearity (R2 > 93%) in three strain ranges. The coupled elastomer nanocomposite layer is utilized to confine the crack evolution resulting in significantly improved stability and reproducibility (>10,000 loading-unloading cycles). Application of such bilayer construction also processes fast response time (<10 ms) and cyclic drift less than 0.01% in human motion detection. Piezoresistive responses of sensors can be designed and effectively tuned to meet specific requirements through the choosing of CNT sponge properties and control of individual layer thickness.