Fabrication Of Flexible And Wearable Triboelectric Nanogenerators For Self-Charging Powered Package

With the development of the Internet of Things(IoT),wearable electronics are becoming more and more popular in our daily life,such as smart watches,smart glasses and so on.At present,these electronic devices are mostly powered by traditional batteries which are generally made of hard materials and has limited lifetime.Moreover,these batteries are required to be charged or replaced from time to time and would bring some environmental pollution as well All these existing problems have greatly limited the real application and further development of wearable electronic devices.Therefore,to develop a flexible and wearable power supply device has become a hot research topic.Among the studies of flexible and wearable powersupply devices,a feasible strategy is to combine energy harvesting device and energy storage device to form a self-charging powered package to drive wearable electronic devices.Compared with other energy haversting devices,triboelectric nanogenerators are considered as a new generation of promising energy harvesting devices because of their light weight,simple structure,low cost and wide selection of materials.Although the traditional triboelectric nanogenerators are made of flexible materials,when harvesting irregular human motions,such as tension,twisting and bending,the structures of these traditional flexible triboelectric nanogenerators would be damaged so as to reduce their output performance.Hence,developing wearable triboelectric nanogenerators that can adapt to irregular human motions has become one of the research focus of this thesis.Meanwhile,in the construction of self-charging powered package,the flexibility and wearability of energy storage device is also very important.Therefore,the other research focus of this thesis is to build a wearable self-charging powered package to drive wearable electronic devices.Considering the two research focuses,based on the material selection and structure design,wearable triboelectric nanogenerators which can better meet the requirements of irregular body motions are prepared in this thesis.Also,the wearable self-charging powered package based on energy harceating devices and energy storage devices has been obtained.The main results are as follows:(1)Using liquid metal-Galinstan as electrode material,silicone rubber as triboelectric material and packaging material,we successfully fabricated a super-strechable triboelectric nanogenerator(LM-TENG).Because of the relatively low Young's modulus of liquid metal,the strain of LM-TENG is only determined by that of silicone rubber,which could be up to 300%.When the liquid metal is exposed to air,a natural oxide film will be formed uniformly and densely on the surface instantaneously,which could effectively prevent the further oxidation of the inner liquid metal,and at the same time avoid the leakage of liquid metal from the silicone rubber so as to greatly improve the stability of LM-TENG.In terms of electrical output,LM-TENG exhibits the highest output performance among single-electrode stretchable TENGs due to the extremely high conductivity of liquid metal.With the contact area of 3 × 6 cm2,the short-circuit current(ISC),open-circuit voltage(VOC)and transferred charge(QSC)of LM-TENG can reach 15.6?A,354.5 V and 123.2 nC,respectively,at 3 Hz.Meanwhile,the good fluidity of liquid metal ensures good electrical output performance of LM-TENG under different deformations.Besides the bulk-shaped LM-TENG,we also designed bracelet-like and fiber-shaped LM-TENG to collect the mechanical energy generated by various parts of the human body.In addition,we combine LM-TENG with rectifier and commercial capacitor to build a self-charging powered package,which could successfully drive some electronic devices such as pedometers,mini-calculators and digital watches.(2)We successfully fabricated a coaxial self-charging powered fiber by using carbon fibers as electrode materials,H3PO4/PVA as solid electrolyte,and silicone rubber as triboelectric,packaging and seperating materials.Here,the coaxial fibers are fabricated with energy storage device-supercapacitors(SC)inside and energy harvesting device-triboelectric nanogenerators(TENG)outside.The two functional devices are seperated by silicone rubber to prevent mutual interference.This is the first time that two functional devices have been successfully assembled in the same fiber.The diameter of the coaxial fiber is only 2 mm,which is smaller than most reported TENG fibers.Also,it has good flexibility which is the basis of fabric weaving.In coaxial fiber,SC has excellent electrochemical performance and durable stability with the specific mass capacitance of 31.25 mF/g.After 6000 cycles,the capacitance value can still keep about 80%.At the same time,when the motion frequency is 2.5 Hz,the electrical output of the TENG part outside the coaxial fiber can be 42.9 V for Voc,15.1 nC for Qsc,0.51,uA for ISC and 1.12?W for maximum output power.Based on the coaxial fibers,we weave them into self-charging powered fabric.By constantly tapping the TENG part of the fabric,the internal SC part would be charged and then used to drive wearable electronic devices.