High-performance triboelectric energy harvester for self-powered system

Abstract

The ongoing worldwide energy exhaustion and environmental pollution issues caused by conventional energy sources such as fossil fuels have become serious concerns over the past few decades. Energy harvesting is an efficient and eco-friendly technique to convert various environmental energies to useful electrical energy. As mobile electronic devices and wireless sensors have dramatically advanced recently, the importance of small-size energy harvesters is rapidly increasing. Power requirements of such mobile devices are small enough that they can be operated with a battery, but the unavoidable recharging and replacement process is a critical limitation. A primary purpose of energy harvesters is to extend the operation time of batteries and, ultimately, to allow for self-powered systems that do not require batteries. A great deal of research efforts have been devoted for the effective harvest of ambient energy sources such as solar energy, wind, ocean waves, subtle mechanical vibration and so on. This paper includes three types of energy harvester using triboelectricity for self-powered system. In the first part, large-area nanopatterning is introduced on a flexible gold substrate by block copolymer (BCP) lithography. Applying this method, we fabricate ultrahigh power energy harvesting harvester based on contact-electrification principle exploiting the effective contact area enhancement. Owing to surface area enhancement by BCP nanopatterning, significant enhancement of triboelectric charge induction is achieved. Those values indicate one of the highest device performance ever reported for the TENGs based on contact-separation mode thus far. In the second part, a casting process with various grain sizes of a sugar template for different pore sizes by three-dimensional soft lithography is proposed to fabricate a triboelectric sponge (TES) with superhydrophobicity and elasticity, which are essential factors for immunity to the effects of humidity and to impart good mechanical stability. This unique micro-nano structure in the TES enhances the electrical output performance due to an increased effective contact area. Additionally, the fabricated TES films have the property of superior robustness and superhydrophobicity of the flat film due to resistance against external environments stemming from its porous morphology. In the last part, powder-based triboelectric energy harvester using polytetrafluoroethylene powder as a freestanding triboelectric layer is introduced. By employing powder, which has fluid-like characteristics, the device is able to harvest random vibrational energy from all directions and can be fabricated regardless of the size or shape of its container.