Composited Pressure–Velocity Sensor Based on Sandwich-Like Triboelectric Nanogenerator for Smart Traffic Monitoring

With the increase of urbanization in modern society, road safety has become a pivotal issue of smart cities. The development of road safety monitoring is concentrated on the innovation and progress of sensors. Here, an all-in-one customizable pressure–velocity sensor (PVS) is developed for simultaneous monitoring of road traffic flow and vehicle velocity. The inclined dielectric-electrode middle layer with gradient structure and grid electrode is designed to eliminate errors caused by data fluctuations and improve sensor sensitivity and monitoring reliability simultaneously. Under a pressure of 13 N, the sensitivity of the PVS to measure velocity is 375.39 mV/mm/s. By designing the geometry of the intermediate layer as an inclined sandwich “return” structure, it is possible to improve the sensitivity of pressure measurement without changing the volume of the PVS. By using a grid structure and an inclined “return” structure, the measurement pressure error range of the PVS can be reduced to 1 N. The design of inclined sandwich “return” structure also reflects the customizability of the PVS. The PVS can still output signals normally after 10 800 working cycles. With the advantages of easy installation, low cost, simple structure, easy maintenance, high integration, and self-powered, the PVS is a promising sensor for road safety monitoring in the development of smart cities.