Design and Application of Nano-engineered Functional Surfaces based on Electrochemistry for Practicalization

Abstract

Nano-engineered functional surfaces have been studied by modifying the wettability to create a surface that satisfy its purpose. In this research paper, we have studied the fabrication process that can improve the practicality of functional surfaces, and the possibility of practicalization of functional surface structures by applying triboelectric nanogenerators as a representative example to proceed with practical use. Superhydrophobic surfaces have gained significant attention due to their ability to enhance performance and introduce novel functionalities in various industrial applications. However, maintaining the integrity of these surfaces against mechanical damage and wear has been a challenge. While strategies such as incorporating unique microscale structures or using self-healing materials have been explored to improve the durability of superhydrophobic surfaces, they are often limited by the requirement for specific thermodynamic stimuli or limited repairability depending on the healing materials used. To overcome these limitations, our study presents a versatile coating method for selectively repairing severe damages on superhydrophobic surfaces. This method involves the construction of surface structures through electrophoretic deposition and hydrolysis of aluminum nitride (AlN) nanopowders without the use of any binder resin. Additionally, a water-soluble adhesive was employed as a temporary protective layer for electrophoretically deposited AlN powders, facilitating the uniform development of hierarchically structured aluminum hydroxides with excellent adhesion to various electrically conductive substrates. These advancements enable successful repair of the wettability of partially and severely damaged samples, consequently extending the service life and expanding the industrial applications of superhydrophobic surfaces. Due to the increasing demand for wearable devices and miniaturization of various electronic devices, the trend of nanofabrication in IT devices is underway. In order to overcome the limitations of battery size and capacity, there has been a lot of research interest in energy harvesting technology, also known as triboelectric nanogenerator. Triboelectric nanogenerators have high efficiency for irregular energy in the low-frequency region, and output performance increases in proportion to the contact area, so many studies have been conducted on increasing the contact area by applying nanostructured surfaces. Thus, we conducted the following two studies to confirm the feasibility of applying nano-engineered functional surfaces to triboelectric nanogenerators. First, AAO(Anodic Aluminum oxide) coated with fluoride is a structure that includes an anode layer with high properties in the triboelectric series, an dielectric layer that helps transfer the triboelectrically generated charges to the electrode without loss, and the electrode. For these reasons, AAO has been a lot of research on its application to frictional energy harvesting nanogenerators. In this work, we analyzed the correlation of AAO between the surface morphology and thickness of the insulating layer by utilizing aluminum oxide, which is advantageous for the application of triboelectric nanogenerators, and adjusting the thickness of the insulating layer. Next, Water waves present a promising and renewable energy source, although their unpredictable motion and low frequency pose notable challenges in harnessing their energy. In this study, we propose a novel solution called the spherical hybrid triboelectric nanogenerator (SH-TENG) specifically designed to efficiently capture the energy from low-frequency, random water waves. The SH-TENG demonstrates a unique capability to convert the kinetic energy of water waves into both solid-solid and solid-liquid triboelectric energy using a single electrode. We conducted an extensive investigation into the electrical output of the SH-TENG, considering its response to the six degrees of freedom motion in water. Additionally, we evaluated the charging performance of a capacitor to showcase the SH-TENG's potential for hybrid energy harvesting from multiple sources using a single electrode. Our experimental results provide compelling evidence for the tremendous potential of SH-TENGs in self-powered environmental monitoring systems. These systems can effectively monitor essential factors such as water temperature, water wave height, and pollution levels in oceans without requiring an external power source. By utilizing SH-TENG technology, we aim to advance the development of sustainable and self-sufficient environmental monitoring solutions.