We are focusing on establishing self-powered and portable electronics systems based on energy harvesting technologies, mainly piezoelectric and triboelectric nanogenerators. The demand of portable and miniaturized electronics is rapidly growing for their use in IoT sensors, wearable devices, and health diagnostic systems. Conventional energy sources are heavily relying on Li-ion batteries that has limited life span, thereby requiring their replacement or recharge frequently. Energy harvesting technologies are of great interest to extend the battery lifetime by converting ambient energy into electric power. For example, a nanogenerator-integrated touch panel, without any external power sources, can detect various types of mechanical stimuli, such as texture, pressure, sound, and so on. Also, we are conducting computational simulations, such as Density Functional Theory (DFT), to quantitatively investigate material properties, thereby securing an improved power-generating performances of the nanogenerators. In summary, we are performing a series of research that covers material study, device structure optimization, and circuit design to realize self-powered systems, which is expected to settle existing energy and environmental problems.

    Meanwhile, recent research outcomes in our lab suggest that triboelectric nanogenerator (TENG) is a powerful candidate for energy solutions in biomedical technologies (A. Implantable medical devices, and B. Pathogen control systems).

A. Worldwide paradigm shift, from wearable to implantable electronics, has been implemented to extend human life expectancy, especially among global IT companies. Various types of implantable medical devices, including pacemakers, neurostimulators, and insulin pumps, have been developed to perform their therapeutical (diagnosis, treatment, rehabilitation) purposes. Since they are only powered by conventional Li-ion batteries, secondary surgery, which endows serious physical/physiological burden to patients, is required to recharge or replace the batteries. We are developing energy solutions for implantable medical devices using biosafe energy sources. In addition, the exploitation of biodegradable materials provides a promising way to develop TENG-integrated electroceutical applications.

B. Due to the pandemic outbreak, we paid enormous economic and social costs. Since developing a target vaccine requires a long period (several years), proper methods to protect humans against viruses and bacteria are mandatory before the vaccine development to reduce the economic and social costs. We found that viruses and bacteria exhibit their own surface potential, so they can be controlled using electricity. We are developing pathogen control systems using human motion-driven TENGs that can be utilized in real world.

    We also have investigated two-dimensional (2D) materials such as graphene, h-BN nanosheet, transition metal dichalcogenide (TMD) nanosheet. We synthesis large scale and high quality 2D materials and design/develop electric device utilizing 2D material`s special and outstanding property. Until now, 2D materials have confirmed its optic property, mechanical property, electric property for various electric applications. Even though 2D materials have unlimited potential, still realizing device is much challenged. One of the difficult things is large scale & high-quality growth of 2D materials and the other is sensitivity of 2D materials which are easily affected by various interface coupling effects to change its property. In conclusion, we synthesis large scale & high quality 2D materials based chemical vapor deposition and we investigate optic & electric property of homo/hetero 2D materials structure with 2D/other bulk materials. We also focus on to realize developing/design 2D electronics.