Widening the Sensing Range of Piezoresistive Composites by Constructing Multilevel Porous Structure

Piezoresistive composite is one of the promising candidates for wearable and flexible force sensors due to its simple and low-cost preparation and conformability to various surfaces. However, it is challenging to achieve a wide sensing range and a high sensitivity simultaneously. Herein, it is proposed to use multilevel porous structure to address the conflict between sensing range and pressure sensitivity. The multilevel porous structure consists of alternately stacked polyacrylonitrile nanofibers and silver nanowires. The nanostructure presents a multilevel deformation when increasing the applied pressure. The sensor has a broad sensing range while maintaining its sensitivity. These results show that the pressure sensor has a superior sensitivity (defined by the resistance change ratio per unit pressure) of 0.437 kPa(-1) and a wide stress range of 0-48.4 kPa. The unique multilevel porous structure makes the sensor stable, repeatable, and durable even after a test of 8000 cycles. Moreover, the sensor also shows small size and lightweight which can be used to detect the movement of various body motions, including facial muscle movements, vocalization, and joint motions. This work provides an effective strategy to achieve high sensitivity and a broad range of piezoresistive sensor through rationally building a multilevel porous structure.