Spacer-free High-output Human Body Kinetic Energy Harvester


Student thesis: Doctoral Thesis

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Award date14 Jul 2020


Given the overwhelming energy crisis and ecological deterioration, the development of renewable green energy source is highly urgent. As one of the most abundant green energy sources, mechanical energy was waste in the past. Thanks to the advent of triboelectric nanogenerator (TENG), a kind of energy harvester makes it possible to effectively scavenge mechanical energy. Owing to its high conversion efficiency and broad materials selection, TENG has attracted considerable attention and shows great potential use in wearable electronics. As the application terminal of wearable electronics, human body is an inexhaustible kinetic energy source. Therefore, it is highly promising to develop wearable TENG for human body kinetic energy harvesting, where free spacer and high output response to human motions are the key motivation of this study aiming at device encapsulation and wearable applications. To this end, various approaches including hybrid effects introduction, triboelectric surface modification, and electrodes improvement, are investigated.

Considering the complex structure and encapsulation of many piezo-triboelectric nanogenerators (PTNGs) resulting from the independence of piezoelectric and triboelectric materials and the need for multilayers, the electrospun composite nanofibers are regarded as piezo-tribo-materials. The fabricated spacer-free PTNG with simple structure shows high sensitivity to minute body movements in both single-electrode and two-electrode modes, due to the rough nanofibers surface and the small inter-fiber distance.

Since specialized equipment is needed for physical surface modification and environmental issues are caused by chemical surface functionalization, rough PBS films based on the polycondensation synthesis that is considered as a green surface selfmodification process, is developed. The spacer-free PBS-based TENG not only shows 3.5 folds that of reported TENG based on PLA and PCL, but also acts as pressure and angle sensors with high accuracy for use in health monitoring with high sensitivity.

Further, spacer-free liquid single-electrode (LS-TENG) using GO dispersion as liquid electrode is developed. This device shows high output response to body motions based on skin, clothes and metals, owing to the high charge mobility of liquid and the charge network role of GO. To further monitor minute body motions, sustainable spacer-free LS-TENG based on AVG@NaCl is also explored, where AVG and NaCl are considered as charge channel and conductive additive, respectively. Therefore, AVG@1wt%NaCl LS-TENG shows high JSC that is 2.1-23 folds of reported LS-TENG and is able to detect face expressions such as frowning and blinking.

This research work provides some insights on the strategies to enhance the output of the spacer-free human body kinetic energy harvester and its sensitivity to minute body motions via structures, materials and electrodes aspects. The developed spacer-free human body kinetic energy harvester shows promising application prospects in wearable and implantable electronics.