| With the rapid development of Internet of Things technology,big data,artificial intelligence and other new-generation information technologies,the demand for various sensors for interactive communication increases sharply.So,how to solve the power supply problem of massive sensor nodes has become the bottleneck of the imodern information technology development.It is an effective solution to break the limitation of traditional power supply method by transforming abundant,widely distributed and renewable clean energy into electric energy to drive wireless sensor network nodes through energy harvesting technology.The triboelectric nanogenerators（TENGs）as a new energy harvesting technology with unprecedented output performance and relatively low cost,have been demonstrated as a leading candidate for numerous applications in energy harvesting and self-powered sensing.However,the problem of low output power is becoming more and more prominent in the process of its engineering application,which has become the bottleneck in its further promotion and application.The surface charge density is a critical factor for TENGs to enhance their output power,thus we explore a series of unique methods to increase the surface charge density in this paper.The details of this research are listed as follows:（1）A surface charge raising strategy for TENGs based on dipoles was proposed.The TENG increases the charge density on the contact surfaces by taking the advantage of ferroelectric characteristics of polyvinylidene fluoride（PVDF）,and the specific research contents are as follows:the PVDF films were first prepared by casting process,and the effects of film thickness and polarization electric field intensity on PVDF piezoelectric properties were studied;Then PVDF piezoelectric films were embedded into TENGs,and the effects of PVDF embedding direction,film thickness and polarization strength on the output of TENGs were systematically studied.The results showed that the TENG embedded the PVDF film with a thickness of 110μm successfully raised the surface charge density of the TENG from 48μC/m2 to 76.8μC/m2,and the surface charge density increased by 1.6 times.A TENG with double helix structure was constructed based on origami folding technology（DHS-TENG）,and the coupling between the composite film and advanced devices was successfully realized.The flexible double-helix-structure features its excellent elastic property without external support materials.The reported DHS-TENG can deliver a peak output power of 9.03 m W under a loading resistance of 4 MΩas well as get an enhanced output performance of 460 V,140μA and 400 n C under a constant contact force of 40 N.Furthermore,the DHS-TENG was capable of powering 120 green LEDs and a temperature sensor.Finally,a remote intelligent switch control system based on the DHS-TENG was constructed due to its good elastic structure performance and electrical output performance.This research not only developed a new strategy to improve the surface charge density of TENG,but also provided a new idea for its application in intelligent home control system.（2）An approach was demonstrated to effectively enhance the surface charge density of TENG while reducing the output impedance of TENGs by utilizing grating-electrode enabled surface plasmon excitation.The theory that the hot electron-hole pairs decayed from the surface plasmon resonance could effectively enhance the surface charge density of the TENG while reducing its output impedance was constructed.Limited by the difficulty of grid-like electrode processing technology and the high processing cost,the effect was demonstrated via inexpensive and disposable plastic gratings on commercially available compact disks（CDs）and digital versatile disks（DVDs）.The results show that the grating coupled surface plasmon resonance on the CDs and DVDs could significantly improve the surface charge density of TENGs and reduce their output impedance.To further verify this effect,a series of TENGs with different line densities（0,100,300,600 lines per mm）on the bottom electrode were developed,and the effects of grating line density,light intensity and light wavelength on the output performances of TENGs were systematically studied.The results show that the outputs of TENGs were positively correlated with the linear density and light intensity.The output performance of the TENG with the line density of600 lines per mm on the bottom electrode exhibits a remarkable improvement on the surface charge density by about 1.87 times while its output impedance is reduced more than 4 times.Furthermore,through light and dark treatment experiments,it verified that the enhancement is not due to the instantaneous effect of surface plasmon resonance,but the hot hole-pairs effect.Finally,a self-powered ultrasonic ranging system based on TENG with the line density of 600 lines per mm was built,and a power management circuit based on LTC3106 module was designed.After charging a 2000μF electrolytic capacitor continuously for 30 minutes through a linear motor,the voltage was charged from 0 V to 5 V,and it can achieve data transmission between transmitter and receiver up to 16 times.This work provided a brand-new application of TENG in self-powered sensing system.（3）Doping nanoparticles into dielectric films is one of the simplest and most effective strategy to improve the dielectric properties of dielectric films.At present,doped materials can be divided into two types:conductor nanomaterials and insulator nanomaterials.Conductor nanomaterials have problems of the large potential energy on the surface of metal nanoparticles,easy agglomeration and easy seepage,while insulator nanomaterials have problems of limited dielectric constant and limited lifting effect.Therefore,a strategy for TENG surface charge density enhancement doped with SiO2@Ag composite particles was proposed.The effects of metal nanoparticles doping and high dielectric insulating nanoparticle doping on the output performance of TENG were analyzed theoretically.The effects of Ag content and the mass fraction of SiO2@Ag composite particles on TENG output performance were systematically studied.The results showed that the SiO2@Ag composite particles with low Ag content had the best output performance,and when the doping mass fraction was 0.1wt.%,the charge density could reach 241μC/m2,which was about 3.45 times higher than the unadulterated TENG.It is because SiO2microspheres not only play a role in improving the dispersion degree of Ag nanoparticles and the dielectric property of materials,but also have a certain effect in preventing the seepage current.Finally,a self-powered wireless temperature sensing system was built to verify the capability of the TENG in powering portable equipment.This work has certain significance in developing new nanomaterial doping technology. |
