Preparation Of Multifunctional Piezoelectric Nanofibers And Its Application In Flexible Sensors

Flexible sensors based on high-performance nanofiber materials are an important part of intelligent wearable,human motion detection,soft robot and other systems.The development of multifunctional composite piezoelectric materials is of great significance for many future applications in multiple scenarios.However,there are few reports on related researches.The key to the development of high performance and multifunctional piezoelectric materials is to increase the content of poly-vinylidene fluoride hexafluoropropylene（P（VDF-HFP））polarβphase and improve the piezoelectric properties.Although there are many researches on improving piezoelectric properties through modification,the improvement of material properties is limited and the application is relatively single.Therefore,based on electrospinning technology,this paper designs a piezoelectric nanofiber material with multi-functional sandwich structure and double filler system,and applies it to flexible pressure sensor,which widens the application range of the material.The organic piezoelectric materials were modified from three aspects of electrostatic spinning process,structural design and filler system,and characterized by SEM,FT-IR,XRD,DSC,TG,AFM,Mechanical test,Sensitivity test,FL,Ferroelectric test,Electrostrictive and Piezoelectric Output test.The effects of material structure and double packing system on the morphology,crystal structure,thermal properties,mechanical properties,sensitivity,fluorescence properties,ferroelectric properties,electrostrictive and piezoelectric output of P（VDF-HFP）nanofibers were investigated.Sandwich structure composite piezoelectric nanofiber films with high piezoelectric properties,excellent mechanical properties and fluorescence properties were successfully prepared.The research results of this paper can provide theoretical guidance and technical support for the practical application of flexible sensors based on high-performance and multifunctional piezoelectric nanofiber materials.The research contents and results are as follows:（1）Four kinds of Eu fluorescence complexes were prepared and their fluorescence properties were analyzed.Eu（TTA）₃（TPPO）₂ was selected as fluorescence filler and the optimal doping ratio was determined.Through the experimental design of Eu（TTA）₃（TPPO）₂/inorganic filler system and Eu（TTA）₃（TPPO）₂/conductive filler system.The optimal doping ratio and experimental system of inorganic filler barium titanate（Ba Ti O₃）,inorganic filler ferric chloride hexahydrate（Fe Cl₃·6H₂O）,one-dimensional conductive filler carboxylated multi-walled carbon nanotubes（MWCNTs-COOH）and two-dimensional conductive filler graphene oxide（GO）were determined.The fluorescence complex and filler were introduced into the polymer matrix by electrostatic spinning technology,and the synergistic effect promoted the increase ofβphase efficiently.Moreover,the sandwich structure nanofiber membrane can promote the mechanical properties,sensitivity,ferroelectric properties,electrodeformation and piezoelectric output of the material,while maintaining the fluorescence properties of the Eu complex.（2）In the Eu（TTA）₃（TPPO）₂/inorganic filler system,the content ofβphase is increased by 20%to 97.5%,the sensitivity is up to 0.49 k Pa^-1,and the output voltage is up to 3 V.At the same time,due to the excellent ferroelectric properties of inorganic filler Ba Ti O₃ nanoparticles,the sandwich structure of PU/PFPCB/PU films exhibits good ferroelectric response at room temperature.The discharge energy density（U_e）is 30.45m J/cm³,which is twice of that of monolayer.It can be used in energy storage devices in addition to flexible sensors.The addition of inorganic filler Fe Cl₃·6H₂O increases the content ofβphase to 96.9%.The sandwich PU/PFPCFe/PU nanofiber membrane has better mechanical properties,with Young’s modulus of 2.3 MPa and strain up to 230%.The mechanical properties are better than those of inorganic filler Ba Ti O₃ system,which are 2.5 MPa and 180%.Piezoelectric output is up to 3.7 V.（3）In the Eu（TTA）₃（TPPO）₂/conductive filler system,the performance of two-dimensional conductive filler GO is much better than that of one-dimensional conductive filler MWCNTs-COOH.Theβphase content of Eu（TTA）₃（TPPO）₂/GO system increased by 96.3%.Used as sensors with excellent sensitivity up to 0.72 k Pa^-1,ultra-high output voltage of 4.5 V and electrostrictive variable of 7 mm,which are 2.4 times of the sensitivity of dual filler Eu（TTA）₃（TPPO）₂/MWCNTs-COOH system(0.3k Pa^-1),2 times of the output electric voltage（2.1 V）and 1.4 times of the electrostrictive variable（4.8 mm）.Young’s modulus of 1.0 MPa is also slightly lower than that of 1.2 MPa in one-dimensional conductive packing MWCNT-COOH system,but the content ofβphase is slightly lower than that of 97.3%in MWCNT-COOH system.（4）Inorganic filler system materials have higher ferroelectric characteristics,which provides the possibility for its use as energy storage devices.The mechanical properties of conductive filler system are obviously better than that of inorganic filler system,and Young’s modulus is greatly reduced.Based on the excellent conductivity of conductive filler,nano-fiber membrane is endowed with excellent electrostrictive characteristics under the application of electric field,which opens up the application of piezoelectric nano-fiber modified material for soft brake.The flexible sensor based on electrospun sandwich structure double filler nanocomposite fiber has ultra-high and low voltage sensitivity,high voltage electrical output,good fluorescence function,excellent Mechanical properties and thermal performance.It has great application potential in the field of multifunctional flexible sensor energy storage,actuators and other fields.