Highly Sensitive Flexible Piezoresistive Sensor with 3D Conductive Network.

The flexible piezoresistive sensor has attracted more and more attention in health monitoring as a man-machine interface due to its simple structure and convenient signal reading. Herein, a highly sensitive flexible piezoresistive sensor with a 3D conductive sensing unit is presented. The 3D conductive sensing unit consists of a 3D network thermoplastic elastomer (TPE) substrate fabricated by fused deposition molding (FDM) 3D printing and carbon nanotubes (CNTs) conductive layer embedded into the surface of the TPE substrate. The finite element analysis (FEA) shows that the 3D network structure has excellent mechanical properties, which is basically consistent with the experimental results. Experimentally, based on the novel 3D conductive network, the flexible piezoresistive sensor exhibits superior comprehensive properties in the compressed or stretched state. The sensitivity of the sensor is as high as 136.8 kPa at an applied pressure <200 Pa while compressing, and its gauge factor (GF) can reach 6.85 while stretching. Meanwhile, the sensor shows excellent stability and durability performance because CNTs embedded into the surface of the TPE substrate have little effect on the flexibility of the elastomeric composite of the sensor. Finally, the piezoresistive sensor is used for detecting subtle muscular movements (facial expressing and throat swallowing) and body movement like arm bending. These results indicate that the novel 3D conductive structure provides an alternative way to improve the performance of piezoresistive sensors and extend their potential applications in health monitoring.