연구홍보포털

논문 초록 (Abstract)

Due to the global energy crisis and environmental problems such as global warming, energy harvesting technology has emerged as an alternative to current energy technology. Sustainable and eco-friendly energy harvesting from surrounding environment, such as solar energy, wind, tide, and mechanical vibration, has attracted a great deal of attention as researchers attempt to solve the worldwide energy crisis.1 Thus far, diverse types of energy sources have been converted into electricity based on various physical principles, such as piezoelectric,2-6 thermoelectric,7-9 and electromagnetic effects.10-12 Among the various ambient energy sources, mechanical energy has attracted much research interest due to its universal availability. Triboelectric energy harvesting based on the coupling of the triboelectrification and electrostatic induction is superior to other energy harvesting technologies which convert ambient energy into electricity due to its high efficiency, eco-friendly process, and inherent low-cost manufacturing methods.13-16 However, the output power should still be enhanced to better meet practical needs, and the working ability for practical applications should be investigated further. Therefore, a surface modification technique is an appropriate solution for high-power generation due to the drastic increment of the effective contact area.17-33 Furthermore, the output performance of a previously reported triboelectric nanogenerator is degraded remarkably by ambient humidity and long-term operation. Thus, designing a triboelectric material which is capable of output performance over the long term and which shows no degradation in very humid environments is a major challenge for the realization of a triboelectric nanogenerator that meets practical needs and applications. Herein, we propose a novel triboelectric sponge (TES) with superhydrophobicity and elasticity which are essential for humidity resistance and for durability. The proposed sponge is made of highly compressible porous polydimethylsiloxane (PDMS) film fabricated by 3D soft lithography. The proposed TES is a generic family of the traditional triboelectric nanogenerator (TENG). The output voltage and current from the TES increase up to peak-to-peak values of 450 V and 0.14 mA cm−2, respectively. This is a ten-fold power enhancement compared to those of a control group (flat PDMS film) under the same mechanical force. The electrical output performance of the TES was measured under wide ranges of mechanical stress. Various TESs were also fabricated using different grain sizes of cube sugar for various pore sizes. The output voltage and current density increase with a decrease in the pore size of the TES. Compression measurements were also conducted to evaluate the resistance to deformation by external force. These experiments showed that the elastic modulus decreases by more than 30% in a sponge type-PDMS film. Thus, the TES become more flexible, and simultaneously the contact area by the micro structure increases when external mechanical force is applied. In addition, we report a very stable and high output performance of the TESs under a wide range of humidity conditions. We also show that a large number of light-emitting diodes (LEDs) can be powered by electrical output power generated by the TES under the application of mechanical strain, even in very humid conditions.