3차원 기공구조를 이용한 정전기반 에너지 하베스팅 나노발전기 소자제조

3D Porous Foam-based Triboelectric Nanogenerators for Energy Harvesting

Abstract

본 연구에서는 3차원 기공구조를 지닌 금속 및 고분자 소재를 이용한 수직 마찰모드의 정전기반 나노발전기(triboelectric nanogenerator, TENG) 제조기술을 소개하고 이에 관한 응용 연구를 수행하였다. 다양한 장점을 지닌 3차원 기공구조를 활용하여 설계된 간단하며 효율적인 나노발전기로, 반복적인 접촉/분리를 통해, 120 V에 이르는 순간 전압특성과 최대 출력 $0.74mW/m^2$을 획득하였다. 실제적인 응용 연구로 48개의 발광소자 구동 실험을 실시하였으며, 저전력 소비 전자소자 장치로의 응용 확장성을 확인하기 위해 회로 구성을 통한 커패시터 축적기능을 확인하였다. 본 연구에서 소개하는 정전기반 에너지 하베스팅 기술은 매우 경제적으로 제조할 수 있는 실용적인 접근방식으로, 반복적으로 가해지는 마찰에 의한 정전력을 효율적으로 획득하여 가까운 미래에 자가발전(self-powered)형 소형 전기소자 구동, 휴대형 전자기기 및 대규모의 전자 발전 장치에 적용 가능할 것으로 기대된다.

Here, we present a facile route to fabricate a vertically stacked 3D porous structure-based triboelectric nanogenerator (TENG) that can be used to harvest energy from the friction in a repetitive contact-separation mode. The unit component of TENG consists of thin Al foil electrodes integrated with microstructured 3D foams such as Ni, Cu, and polyurethane (PU), which provide advantageous tribo-surfaces specifically to increase the friction area to the elastomeric counter contact surfaces (i.e., polydimethylsiloxane, PDMS). The periodic contact/separation-induced triboelectric power generation from a single unit of the 3D porous structure-based TENG was up to $0.74mW/m^2$ under a mild condition. To demonstrate the potential applications of our approach, we applied our TENGs to small-scale devices, operating 48 LEDs and capacitors. We envision that this energy harvesting technology can be expanded to the applications of sustainably operating portable electronic devices in a simple and cost-effective manner by effectively harvesting wasted energy resources from the environment.

Fig. 1. 3D porous foam-based TENG. (a) A schematic illustration of a TENG structure and a representative SEM image of 3D Ni foam. (b-d) The construction process of a vertically stacked TENG using PMMA sheets connected with struts and springs, a 3D porous foam, and a sheet of flat PDMS

Fig. 3. Electrical measurements of the Ni foam-based TENG in vertical contact-separation mode. (a) The open-circuit voltage and (b) the short-circuit current by the repetitive periodic contact-separation. (c) Dependence of the output voltage and current with the increased load resistance. (d) Load resistance versus power peak value of the nanogenerator.

Fig. 4. Electrical performance of Cu and Pu foam-based TENGs. (a) The optical microscope image of the surface of Cu foam (left). The open-circuit voltage and the short-circuit current density were ~80 V and ~1.5 μA, respectively (middle-right). (b) The optical microscope image of the surface of PU foam (left). The open-circuit voltage and the short-circuit current density were ~42 V and ~0.2 μA, respectively (middle-right).

Fig. 2. Schematics of operating principle of a 3D foam-based TENG. (a) Initial state where the external load is not applied and separated with an optimum distance, dn. (b) When the 3D porous foam is brought into contact with the PDMS sheet by the external load, the triboelectric charge can be generated on each surface of the two materials to balance the surface charge. (c) A potential difference is generated by the separation of the two materials, and the electrons can be induced to the upper electrode. (d) When the two surfaces are fully separated, the surface charge accumulates and equilibrates. (e) By the sequential engagement of the external load, the electrons can be inversely induced to the lower electrode.