정전기 에너지 수확의 출력 제어를 위한 접촉 구조 및 저장층에 관한 연구

Abstract

Demand for wireless and wearable devices has influenced energy harvesting of activity in daily life, and has focused on various charge generating mechanisms such as piezoelectricity, electromagnetic, and triboelectricity. Triboelectric nanogenerator (TENG) has received attention because of high output, low cost, and easy fabrication. Although the TENG has been fabricated in various forms, sharp and irregular peaks are inevitable in triboelectrification. Thus, precise control on the output profile is required for direct application as a power source. Approaches on controlling output profile have been based on enhancing the absolute value of power output and storing the generated charges. Power enhancement was mainly controlled by fabricating surface nano/microstructures to increase surface area, but a large surface area with high density array is difficult to deform when pressed, which limits the actual contact area. The storage of output power in the connected capacitors has shown generation of DC voltage, but recent researches with a rigid commercial capacitor and high-frequency requiring battery have limited control on voltage profile. In this thesis, to achieve specific output control of TENG, a new surface structure and storage layer are introduced. In chapter 2, thin film-covered pillar structure was suggested as a strategy to achieve full contact area for high triboelectric power generation. In addition, it was discussed on the importance of adhesion energy as a parameter in the triboelectric energy harvesting. Both the pillars and the film were made of polydimethylsiloxane (PDMS) with low modulus. The electrical power was highly increased compared to the conventional structures (flat film and pillar-only structure). The dependence of power generation on the thickness of the thin friction layer and the adhesion energy was quantitatively investigated. In chapter 3, I proposed a simple approach to change the spike-like voltage profiles to square-like profiles and adjusted the output voltage working suitable electronic devices. With printed ion gel electrolyte patterns as a capacitor, I investigated the effects of dimension of the capacitor, connection types (serial, parallel) of multiple capacitors, and presence of electrochemilulminescence dye in the ion gel. The voltage profile of the TENG-ion gel system was modulated by the contact frequency applied to the TENG, the contact area of the ion gel with the electrode, the type of ions in the electrolyte, reduction/oxidation reaction in the gel, and the connection type (parallel, series) between ion gel patterns. In chapter 4, a constant DC output voltage and its modulation to a target value were accomplished. A full bridge rectifier was used for DC conversion and an electrolyte-based electrochromic supercapacitor (ion gel/WO3) was used as a charge storage unit. The relaxation profile of the ion gel/WO3 supercapacitor increased considerably the charge relaxation time by a large offset voltage compared to a simple ion gel capacitor. I demonstrated that the constant DC output voltage can be modulated by adjusting the contact area of TENG, contact frequency, and serial/parallel connection of the supercapacitors.