The quest for alternative green energy sources is being steered by the side effects of excessive use of fossil fuels being experienced all over the world. Therefore, developing novel green power production systems of low cost nature is a critical global need. Recently, a technical paradigm occurred to drastically change the viability of personal and wearable electronics through innovative and mobile energy harvesting technologies such as solar, thermal, and mechanical scavengers. Such energy harvesters have been seen applicable in personal electronics and defense technologies. A notable example of such energy harvesting devices is the triboelectric nanogenerator(s) which act in either sliding mode or contact mode. Both operation modes are often limited by their short lifetime and low reliability. To be more precise, the slide mode is not popular due to the low operating frequency experienced, material selection and high fabrication cost. On the other hand, rotation is an effective type of motion that can easily provide a high working frequency. Unfortunately, excessive friction encountered leads to high costs and long manufacturing time. In view of this, there is need to develop a sustainable energy generating system for the nanogenerators.
Researchers led by professor Dukhyun Choi from the Department of Mechanical Engineering, Kyung Hee University in South Korea proposed a study to transform rotational motion into linear movement via kinematic design and the use of a cam, thereby allowing the achievement of high speed linear motion. They developed cam-based triboelectric nanogenerators, where the cam would be used to transform rotational motion into linear movement, resulting in a practically-sustainable high-performance scavenger that utilizes contact-type triboelectric nanogenerators. Their work is now published in the journal, Nano Energy.
The researchers fabricated the contact type triboelectric nanogenerators and then proceeded to fabricate the cam-based triboelectric nanogenerators by 3D printer using polylactic acid as the raw material. Eventually, they undertook measurements and characterized the surfaces of the fabricated cam-based triboelectric nanogenerators.
The authors observed that the rigidity of the supporting substrate below the contacting materials was significant and enhanced the output performance of triboelectric nano-generators over twice by adopting soft substrates. More so, they noted that the ratio between the spring constants of a spacer spring and a bumper spring was an important design variable critical for improving the output power of the cam-based triboelectric nano-generators. Interestingly, they realized that by augmenting the number of cam noses, the working frequency increased, but the output peak power was not changed due to the same contact velocity in the cam-based triboelectric nano-generators.
The study by Dukhyun Choi and colleagues presented an adoptable method that can be used to utilize wasted rotating mechanical energies. In this work, it has been theoretically determined that the output power is critically dependent on the ratio of the spring constants of the spacer and bumper springs. In conclusion, the presented cam-based triboelectric nano-generators represent a practical and promising platform that can be used to create electrical energies by utilizing wasted rotating energies in our environment.
Younghoon Lee, Wook Kim, Divij Bhatia, Hee Jae Hwang, Sangmin Lee, Dukhyun Choi. Cam-based sustainable triboelectric nanogenerators with a resolution-free 3D-printed system. Nano Energy 38 (2017) 326–334
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