Research On The Performance Of Fully Degradable Materials And Devices For Triboelectric Nanogenerators

With the development of the intelligent era and widespread utilization of electronic products,the resulting electronic waste has become to an increasingly and serious problem,and therefore it is urgent to develop green and environmental-friendly electronic devices.Fully degradable triboelectric nanogenerator(FD-TENG)has received widely attention due to its ability to collect mechanical energy from the environment and convert it into electrical energy,and then degrade into water and carbon dioxide as well as environmentally harmless substances.However,the degradable materials are weak in electron gain and loss,which makes the selection of materials for FD-TENG difficult.To address the above problems,we first developed an FD-TENG with graphene composite paper as the electrode and found that the electrical surface microstructure transfer mechanism is beneficial to improve the output performance of FD-TENG in this paper.Subsequently,for the friction layer,different types of degradable materials with different electron affinity were investigated to lay the foundation for the development of high-performance FDTENG.Finally,the FD-TENG device for sensing small vibrations was developed based on the strategy of bionic spider silk.These works will provide new ideas for the development of FD-TENG.The main research contents and results are as follows:(1)A high-performance FD-TENG was fabricated using graphene composite paper as the electrode instead of copper foil,using regenerated cellulose(RC)as the positive friction layer and poly(butylene adipate-co-terephthalate)(PBAT)as the negative friction layer.Under a pressure of 50 kPa and a device size of 2×2 cm2,the FD-TENG shown the output voltage of 100 V,the output current of 7 μA,and the power density of 637 mW m-2,which were 2.22,3.04,and 5.05 times higher than that using copper as electrodes,respectively.Moreover,the FD-TENG showed good stability.The observation of the surface microstructure of the graphene composite paper using a super-depth microscope and scanning electron microscope(SEM)revealed that the output performance was enhanced with an increasement of the roughness of the electrode surface,suggesting that the transformation of the microstructure under pressure increased the effective friction area,thus improving the output performance of the FD-TENG.This strategy may pave a new way for the development of high-performance FD-TENG.Additionally,this FD-TENG is applicable in the fields of energy collection and self-powered sensing,and the output performance can be further improved by grafting amino groups onto the RC surface.Within three months,this FD-TENG can be almost completely degraded in soil,avoiding the accumulation of electronic waste.(2)In addition to the electrode material,the friction layer is crucial in determining the output performance of TENG.Therefore,this paper further studied the electron gain and loss abilities of different degradable materials,with the same film thickness,device size,and operating force,as friction layers.These degradable materials included polybutylene succinate(PBS),polycaprolactone(PCL),poly(butylene adipate-co-terephthalate)(PBAT),polyhydroxyalkanoates(PHA),polylactic acid(PLA),polyvinyl alcohol(PVA),sodium alginate(SA),starch,gelatin,silk,regenerated cellulose(RC),paper,and chitosan(CS).Their electron gain and loss abilities were analyzed when used as friction layers and ranked accordingly,with the series order being PBS>PCL>PBAT>CS>PVA>RC>PHA>SK>Gelatin>Paper>PLA>SA>Starch.Among them,the PBS and SA systems had the best output performance,with an output voltage of 46 V and an output current of 700 nA.When graphene composite paper was used as the electrode,the FD-TENG with PBS and SA as the friction layer had an output voltage of around 88 V and an output current of 1.25 μA.The establishment of this electron gain and loss abilities sequence order sets the foundation for the development of FD-TENG.(3)TENG can be used as a self-powered sensor,but the sensitivity of FDTENG-based self-powered sensors needs to be improved.In this paper,PHA with piezoelectric properties was used to modify PBS,and a single-electrode PBS/PHA-based FD-TENG with a biomimetic spider silk pattern was prepared by electrospinning.The results showed that the micro-nano fiber structure of electrospinning and the introduction of PHA could effectively enhance the sensing sensitivity of FD-TENG to weak vibrations.When PBS:PHA=0.5:1.5,the output was the best,with an output voltage of about 50 V and an output current of 1.2 μA.The highest power density of PBS/PHA-based FD-TENG reached 182 mW m-2 under a load resistance of 70 MΩ.The long-term working stability was demonstrated by 10,000 repeated cycles.Finally,the device was used to detect small vibrations generated by walking and blowing,indicating its good application prospects in vibration sensing direction.