Energy harvest-power MEMS devices for future sensor network society: Stochastic resonance meets TENG device

In 2012, a novel energy harvesting approach was proposed and named TENG (Triboelectric Nano Generator), which is based on the combination of electrification effect and electrostatic induction. Due to remarkable properties, such as high-performance and the use of environmentally friendly materials, TENG has raised increasing interest. Several techniques have been developed to enhance the power density, including structural optimization, operation mechanism, surface texturing and hybrid TENG. Recently, a power density of up to a 19 mW/cm
²
has been reached with an output power larger than 1.5 W. Herein, we propose a very simple and cost-efficient approach to fabricate high-performance TENG based on paper and graphite pencil. In order for TEG to make an impact in real life applications, further improvements are needed in particular in the choice of the pair of electrification materials beyond the conventional materials. The materials used to create the TEG system should ideally be designed to be wearable on the body (or even be implantable) and should therefore be flexible, bio-friendly and biodegradable, and ultimately transparent. Here, not only a paper, a promising material of silk fibroin is successfully utilized to construct transparent TEGs. Several technical challenges have been successfully addressed and are shown. On the other hands, we propose a novel device, which can utilize ambient vibration with wideband and low frequencies. As the power sources of wireless sensors, batteries are mainly utilized until now. These days, devices of energy harvesting become more focused. Energy harvesting is a methodology of scavenging power from ambient energy sources such as solar, thermal and vibration without the need for batteries. Due to high stiffness of piezo electric energy harvesters, resonant frequency of the piezo electric energy harvesters tends to be much higher than ambient vibrational frequency. To solve these problems, the proposed energy-harvesting device is to utilize a stochastic resonance. This paper reports a new hybrid energy harvesting approach which combines triboelectricity and piezoelectricity based on low-frequency stochastic resonance. A vibration configuration was well designed to enhance the conversion efficiency of mechanical energy to electricity via the stochastic vibration mechanism. Furthermore, the electric output performance of the proposed generator is significantly strengthened by adding triboelectric effects to bi-stable structured energy harvester, showing attractive potential for generating high output by harvesting low-frequency energy, typically the living environmental energy like the body motion of human.