Carbon Material Based Stretchable Self-Changing Power Unit

With the rapid development of people’s living standards,flexible electronic devices and intelligent wearable devices have already become an indispensable part in our daily lives.The flexible wearable devices such as electronic skin,smart watch and sports bracelet have got more and more attention.However,one of the major challenges is that all the devices need power source such as batteries to provide electric power.Although the power dissipation of electronic devices has been reduced in a great extent,some problems such as the impossibility of self-powering,frequent battery charging,battery replacement and waste battery treatment still remain when we choose the traditional power supply mode.All this time,we cannot make the best use of the mechanical energy existed in human’s daily movement because of the low vibration frequency.Vibration energy from human motion will certainly be enough to power wearable electronic devices if we can find an appropriate method to harvest it.Zhong Lin Wang’s research group from Georgia Institute of Technology invented a kind of energy collection device called triboelectric nanogenerator(TENG),which can convert vibration energy to electrical energy based on contact electrification and electrostatic induction.In comparison to traditional electricity generation,TENG is fairly suitable to collect low frequency vibration energy.The irregular human motion leads to the unstable voltage and electric current of the collected energy,which cannot directly power the electronic equipment.Thus,it is an urgent need to find a way to manage and store such energy.Supercapacitor is one of the best choice due to its advantages of high energy density,high efficiency and long-life.The self-charging power unit composed of triboelectric nanogenerator and supercapacitor become the research focus recently.While collecting the mechanical energy of human motion,the self-charging power units are usually in different deformations such as stretching,twisting and bending.Thus,flexibility and stretchability should be the essential qualities of this kind of self-charging power units.The main content of this thesis includes:We designed a single-electrode mode TENG,in which carbon paper was electrode material and silicone rubber was dielectric material.In order to realize the stretchability of TENG,carbon paper was folded into the structure in triangular cross section.The highest open circuit voltage of TENG reached 330 V,while the highest short circuit current was more than 18 μA.The transferred charge reached 119 n C.All these data represent promising electrical performance compared to the previous work.We than designed a supercapacitor,using origami carbon paper as electrode material,conductive polypropylene(PP)as membrane material and PVA/KOH as solid electrolyte.Finally,the above-mentioned TENG and supercapacitor were together poured into silicone rubber,becoming a self-charging power system,in which TENG collected energy,while supercapacitor stored energy.The flexible stretchable self-charging system can work in different deformations such as stretching,bending,twisting and rolling.The self-charging system was waterproof,due to the silicone rubber all-coated structure,and it can work in rainy day and there will be no damage to the electrical performance even after washing.We also fabricated a self-charging power unit based on carbon fiber,which is composed of a one-dimensional TENG and an one-dimensional supercapacitor.We first prepared the TENG,in which carbon fiber was electrode material and silicone rubber was dielectric material.The highest open circuit voltage of the TENG reached 48 V,while the highest short circuit current was more than 0.78 μA.The transferred charge reached 17 n C.We than designed a supercapacitor,using carbon fiber as electrode material and PVA/KOH as solid electrolyte.Finally,the above-mentioned TENG and supercapacitor were together sewed on clothing as a serpentine shape.