Self-Powered Intelligent Water Droplet Monitoring Sensor Based on Solid-Liquid Triboelectric Nanogenerator

Abstract

Real-time monitoring of rainwater is a critical issue in the development of autonomous vehicles and smart homes, while the corresponding sensors play a pivotal role in ensuring their sensitivity. Here, we study a self-powered intelligent water droplet monitoring sensor based on a solid-liquid triboelectric nanogenerator (SL-TENG). The sensor comprises a SL-TENG, a signal acquisition module, a central processing unit (CPU), and a wireless transmission module, facilitating the real-time monitoring of water droplet signals. It is worth noting that the SL-TENG has self-powering characteristics and can convert the kinetic energy of water droplets into electrical energy. The excellent output performance, with open-circuit voltage of 9 V and short-circuit current of 2 μA without any treatment of the SL-TENG, can provide an effective solution to the problem that traditional sensor need battery replacement. In addition, the SL-TENG can generate stable amplitude electrical signals through water droplets, exemplified by the absence of decay in a short-circuit current within 7 days. More importantly, the sensor is equipped with intelligent analytical capabilities, allowing it to assess rainfall based on variables such as amplitude and frequency. Due to its excellent stability and intelligent analysis, this sensor can be used for roof rainwater monitoring, intravenous administration monitoring, and especially in automobile automatic wipers and other fields.

Keywords: automobile automatic wiper; intelligent analysis; self-powered sensor; solid–liquid triboelectric nanogenerator; water droplet monitoring.

Figure 1

(a) Structure of the SL-TENG; (b) schematic diagram of the SL-TENG; (c) circuit model of the SL-TENG; (d) basic output performance of open-circuit voltage and short-circuit current based on SL-TENG; (e) hydrophobic angle of upper copper electrode before hydrophobic treatment; (f) hydrophobic angle of upper copper electrode after hydrophobic treatment; (g) comparison of short-circuit current before and after hydrophobic treatment of the SL-TENG.

Figure 2

(a) The open-circuit voltage of the SL-TENG under different water droplet volumes; (b) the open-circuit voltage of the SL-TENG at different drop heights; (c) the open-circuit voltage of the devices are based on FEP film, PTFE film and Kapton film, respectively; (d) the short-circuit current of the SL-TENG at different frequencies; (e) the short-circuit current of devices with different film thicknesses; (f) stability test results of the SL-TENG.

Figure 3

(a–c) Output performance of the SL-TENG under light rain, middle rain and heavy rain; (d) the open-circuit voltage and power of the water droplet monitoring sensor change as the external resistance changes; (e) flow chart of the workflow of the water droplet monitoring sensor; (f) schematic diagram of water droplet monitoring sensor.

Figure 4

(a) Output of water droplet monitoring sensor before calibration; (b) output of water droplet monitoring sensor after calibration; (c) the open-circuit voltage of the SL-TENG at 3.1 °C; (d) the open-circuit voltage of the SL-TENG at 25.2 °C; (e) testing of the water droplet monitoring sensor at different temperatures; (f) the open-circuit voltage of the SL-TENG at 45.8 °C.

Figure 5

(a–c) Water droplet monitoring sensor identifies light rain, middle rain, and heavy rain; (d) the water droplet monitoring sensor detects that the car window is not closed on rainy days; (e) overall diagram of car automatic wiper.