Multi-Hierarchical Microstructures Boosted Linearity of Flexible Capacitive Pressure Sensor

Besides the excellent sensitivity, linearity is also highly required for a miniaturization and low power consumption of the flexible sensor system. Herein, multi-hierarchical microstructures to improve the linearity of capacitive pressure sensor based on poly(vinylidene fluoride)/reduced graphene oxide (PVDF/rGO) multilayer films is designed and constructed. The differentiated hierarchical microstructure in each layer comes from irregular protrusions with various roughness. Excellent sensor performances, such as higher sensitivity (0.18 kPa) in the linear range from 0.1 kPa to 11 kPa, lower limit of detection (100 Pa), rapid response time (56.3 ms) compared with some current reports, are obtained in the sensor based on three laminated films with the successive roughness (remarked as 150/400/800 Cw films). Moreover, the device exhibits outstanding stability over 3000 cycles at a pressure of 10 kPa, and successfully works on the falling leaf of 0.16 g and the weight of 100 g as well as high heel pressure. These outstanding properties are attributed to the compressibility of the hierarchical structure and efficient stress distribution between stacked multilayers, which is verified by using the finite-element analysis (FEA). The work provides a simple and low-cost route for fabricating high-performance capacitive sensors with diverse potential applications in wearable electronics.