Flexible Stretchable Nanogenerator Based On Displacement Current

Energy is the key production means for human activities and the motivation of human civilization development.As global energy problems become increasingly urgent,new energy technology is an effective way to solve current energy problems.Mechanical energy,which is widely distributed and easy to convert,is an important part of new energy development.As a research focus in the field of energy harvesting,triboelectric nanogenerator（TENG）and piezoelectric nanogenerator（PENG）are two important methods to harvest mechanical energy.The physical essence behind the two methods is the maxwell displacement current,which is produced by the electrode relative motion or the material deformation under the external stimulation.With the development of wearable electronic technology,the requirements of relevant additional technologies are constantly updated.Due to the multiple degree of freedom and large strain characteristics of human motion,the traditional rigid devices are no longer suitable for such applications.Therefore,flexible stretchable devices are a hot topic in the field of wearable electronics and energy technology.For TENG,the flexible stretchable device is easy to realize,and the difficulty is the enhancement of surface triboelectric charge density and device output performance.For PENG,piezoelectric effect is closely associated with the special crystal structure,resulting in the narrow material selection ranges.Meanwhile,the high temperature process is necessary for the preparation of piezoelectric materials,so making the flexible stretchable piezoelectric materials and devices a troublesome issue.Aiming at the application of flexible stretchable energy devices in wearable electronics,this paper studies the flexible stretchable functional materials and device structures in TENG and PENG.It includes the output performance improvement of ultra thin flexible TENG,the flexible stretchable piezoelectric materials and devices,the application of TENG and PENG in energy harvesters and self-powered sensors.The main conclusions are as follows:（1）The output performance and the conformal assembly of flexible TENG can be improved by the sacrificial layer pre-deposition and reverse mould method,which can transfer the micro-pyramid array onto the ultra thin flexible triboelectirc material surface and enhance the surface triboelectric charge density.The specific surface area of material can be increased by 2.27 times by the micro pyramid array.The results show that the TENG with an effective area of 4.0×4.0 cm² can directly light up 110 commercial green light-emitting diodes（LEDs）in series.Meanwhile,the TENG has a good conformal assembly as self-powered sensor,which can realize the recognition of human joint motion.（2）In order to achieve the flexible stretchable piezoelectric materials and devices,the piezoelectric composite（with and without Pb）are successfully prepared by the introduction of piezoelectric particles into the polymer with high elasticity（stretching rate up to 600%）using shear force dispersion technology.The peak-to-peak voltages of PbZrTiO₃ composite material and BaTiO₃ composite material can reach 16 V and 38 V,respectively.These composite materials can respond to different external stimulations（such as stretching speed,stretching rate and frequency）,which has potential application in human motion energy harvesting and posture monitoring.（3）In this paper,the triboelectric-piezoelectric hybrid nanogenerator is proposed to improve the efficiency of flexible stretchable energy harvester.The of flexible stretchable hybrid arch nanogenerator combining TENG and PENG can respond to different mechanical stimulation modes（beating and stretching）,and the output performance of hybrid nanogenerator is remarkably higher than individual nanogenerator.On the other hand,based on the flexible stretchable triboelectric materials and piezoelectric materials,the piezoelectric enhanced triboelectric nanogenerator fabric has been realized with excellent mechanical reliability and electrical stability.The open circuit voltage and short current can reach 600 V and 17μA,respectively.This work provides a foundation for the application of flexible stretchable energy devices in wearable electronic.