Highly-Sensitivity and Self-Powered Ocean Wave Sensor Based on Liquid-Solid Interfacing Triboelectric Nanogenerator

Abstract

Accurate forecasts of wave conditions are essential for marine engineering construction, development and utilization of ocean resources, environmental protection, maritime safety and early warning of marine disasters. There are many types of wave monitoring techniques, such as wave rider buoys, acoustic Doppler current profilers, high frequency radar and remote sensing [1]. Due to each of the techniques has its own advantages and disadvantages, it is essential to choose and develop proper techniques according to the requirements and conditions of applications. These commercial wave monitoring techniques are mainly applied for routine monitoring of waves and currents in the offshore and nearshore regions [2, 3]. To enhance the environmental sensing ability of smart marine equipment, it is important to develop a highly sensitive wave sensor to monitor the interaction between ocean waves and marine equipments, such as offshore platforms and ships. In this paper, a novel wave sensor based on liquid-solid interfacing triboelectric nanogenerator (WS-TENG) is proposed and investigated. The WS-TENG is made of a long copper electrode covered by a poly-tetra-fluoroethylene (PTFE) film with a microstructural surface. The effects of substrate, wave height, frequency, and water salinity on the sensitivity of the wave sensor are experimentally studied and analyzed. It is found that the output voltage peak of WS-TENG varies linearly with wave height. The WS-TENG with the electrode width of 10mm has a sensitivity of 0.023 V/mm, suggesting that the present novel sensor can sense the wave height in the millimeter range. The sensitivity would be increased further by widening the electrode, and/or enhancing the surface hydrophobicity. In contrast, the output voltage peak of WS-TENG is independent of wave frequency. Furthermore, the output voltage decays dramatically when water salinity is increased from 0 to 0.035 g mL−1. This may be due to high ions concentration reduces induced charges in electrodes [4]. It is worth to note that the linear relationship between the output voltage of WS-TENG and wave height is still valid at different salinities. In a simulated wave tank, the wave sensor is successfully used for real-time monitoring of the wave around the simulated offshore platform. Therefore, the wave sensor provides an alternative and self-powered approach to monitor waves’ characteristics.