Fabrication Of Flexible Fiber-Shaped Triboelectric Nanogenerators For Self-Charging Power System

In recent years,the potential of wearable electronic devices in the field of Internet of Things has been increasing,whereas the limitation of traditional power sources has always been a huge challenge.To overcome this problem,the wearable power supply,especially the integration of wearable energy harvesting devices and energy storage devices,is a prospective approach.Among various wearable energy harvesting devices,the triboelectric nanogenerator(TENG)has attracted great interest in this field due to its outstanding advantages such as diversified materials,simple structure,low cost,and easy fabrication.Combining advanced triboelectric nanogenerators with traditional textile technology,the fiber-based triboelectric nanogenerators have been emerged,which support the development of smart textiles with mechanical energy collection and multifunctional self-powering,while maintaining a flexible,soft,and extensive wearable application platform.However,during the collection of complex human movements,the traditional triboelectric nanogenerator not only restricts the movement of the human body,but also irretrievably change its output performance after stretching,bending and twisting.Therefore,to improve the stretchability of single fiber to develop a flexible triboelectric nanogenerator fabric suitable for harvesting human motion energy is the first research focus of this thesis.Combining stretchable fiber-shaped energy storage devices to form a self-charging power system to power flexible wearable electronic devices,which is an alternative method to traditional power sources,is the second main point of this thesis.It is critical to further improve the output of the fiber-shaped triboelectric nanogenerator to achieve an efficient self-charging energy supply system.Therefore,to obtain a fiber-shaped triboelectric nanogenerator that has both excellent electrical output performance and unique property as a textile is the third research point of this thesis.Based on the above research focuses,this thesis starts from the structure and material selection of fibers and then reports the preparation of the fiber-shaped triboelectric nanogenerator that is more suitable for human wear.A wearable self-charging power system was constructed in combination with fiber-based supercapacitors.The output improvement of the fiber-shaped triboelectric nanogenerator was studied.The main research results of this thesis are as follows:(1)In this work,we fabricated a fiber-shaped stretchable and tailorable triboelectric nanogenerator(FST-TENG)based on the geometric construction of a steel wire as electrode and ingenious selection of silicone rubber as triboelectric layer.Owing to the great robustness and continuous conductivity,the FST-TENGs demonstrate high stability,stretchability,and even tailorability.For a single device with 6 cm in length and 3 mm in diameter,the open-circuit voltage of 59.7 V,transferred charge of 23.7 nC,short-circuit current of 2.67 μA and average power of 2.13 μW can be obtained at 2.5 Hz.By knitting several FST-TENGs to be a fabric or a bracelet,it enables to harvest human motion energy and then to drive a wearable electronic device.Finally,it can also be woven on dorsum of glove to monitor the movements of gesture,which can recognize every single finger,different bending angle,and numbers of bent finger by analyzing voltage signals.(2)A high-strength fiber based self-charging system was prepared,in which a carbon fiber based triboelectric nanogenerator(CF-TENG)was used as a mechanical energy harvesting device,and the carbon fiber-based twisting supercapacitor(CF-SC)was used as a flexible energy storage device.Sewing every single CF-TENG serpentine on elastic fabric forms a large area of highly stretchable energy-supplying fabric.At 2.5 Hz,the open-circuit voltage(Voc),transfer charge(Qsc),short-circuit current(Isc)and maximum average power of the energy-supply fabric in an area of 5×5 cm2 can reach approximately 186.6 V,63.4 nC,6.6 μA,and 189.5 μW,respectively.At the same time,the single CF-SC has the capacitance of 16.4 μF and can maintain performance even under tensile and bending conditions.The combination of three CF-SCs in series with an energy supply fabric forms a high-strength stretched self-charging power fabric and then drives wearable electronic devices.(3)The TiO2 electron blocking layer(EBL)was prepared and adapted in a carbon fiber-based triboelectric nano-generator(CFT-TENG)to improve its performance.Due to the coupling of electron blocking and polarization enhancement,TiO2 EBL with high dielectric constant increases the maximum average output power of CF-TENG by 12.7 times,the open circuit voltage by 2.86 times,the short-circuit current by 4.1 times,and the transfer charge by 3.39 times(28.65 V,0.74 μA,and 9.82nC,respectively,at 2.5 Hz).During the sample preparation process,the concentration of TiO2 sol was controlled to ensure the integrity and adhesion of the film which can not to be broken.Therefore,the use of EBL in the flexible fiber based triboelectric nanogenerator is beneficial to wearable energy-providing fabric.