Research And Preparation Of Flexible Sensors Of SiO₂ Particles Doped PVDF Nanofibers

Polyvinylidene fluoride(PVDF),as a kind of piezoelectric polymer with stable chemical properties,has excellent ferroelectric,piezoelectric and thermoelectric properties.At present,PVDF has been widely used in intelligent and electronic materials,especially flexible wearable electronic components.In recent years,its research and application in piezoelectric films have been attracting scholars'attention.PVDF-based piezoelectric film has good machining performance,strong flexibility,wide frequency response,good corrosion resistance,light weight and other advantages.It is suitable for wide and suitable application in intelligent wearable field.However,the PVDF crystal structure obtained by conventional means such as casting,casting and spinning is mainly composed of non-polar crystal phase,and the crystal that produces piezoelectric effect has lower piezoelectric energy exchange characteristics,which cannot meet the requirements of flexible piezoelectric sensors.The electric field polarization combined with strong polar inorganic particle doping in the fiber forming process is an effective means to improve the piezoelectric properties of PVDF.In order to optimize the crystal phase in PVDF,the electrospinning process was used to deposit the nanofiber membrane by electronic nanometer SiO₂ particles doping and electrospinning.Among them,nano-SiO₂ particles are ultrafine inorganic particles mainly composed of atomic crystals,with small particle size,large specific surface area,strong surface adsorption capacity,good stability and outstanding bioaffinity.Doping is a good electret in polymers.This article will mixed size 45 nm SiO₂ nanoparticles in the PVDF/n,n-dimethyl formamide(DMF)in the solution system,by adjusting the amount of SiO₂ doping and spinning process,was prepared with high content of beta crystal PVDF piezoelectric fiber membrane,its preparation into with sandwich structure flexible thin film piezoelectric sensors,piezoelectric sensors research as an application of piezoelectric sensors,discusses the high sensitivity of piezoelectric thin film technology in the problem of"their".Specific contents include:(1)The physical characteristics of PVDF/DMF spinning system were studied,and the influence of the viscosity and electrical conductivity of spinning solution with different concentrations on spinning process was emphatically tested.The preparation of nanofibers with 8-10 w.t%high concentration PVDF spinning solution was studied.The morphological characteristics of nanofibers under different electrostatic voltages were regulated to obtain an optimized PVDF nanofiber electrostatic spinning process.(2)Nano-SiO₂ particles with unequal mass fraction of 1-5W.t%were uniformly doped in PVDF/DMF spinning system by solvent doping method.In view of the change of viscosity of PVDF/DMF spinning system caused by SiO₂ particle doping,the spinning process was moderately fine-tuned.The surface morphology of the nanofibers was observed by scanning electron microscopy(SEM),the internal crystal structure was analyzed by X-ray diffraction(Xrd),and the dielectric constant and loss Angle of the nanofibers were measured by dielectric spectroscopy.The results show that although SiO₂doping reduces the content of crystal in PVDF nanofibers,it improves the polarity stability of the structure.The dielectric coefficient of nanofibers obtained by 2w.t%SiO₂ doping was the highest,reaching 5.4.(3)A thimble polarization device with silicone oil isolation was constructed,and the SiO₂/PVDF nanofiber membrane was heated and electrically polarized at a TEMPERATURE of 90? to enhance the polarity of the membrane.The polarization electric field intensity and polarization time,and the axial piezoelectric conversion coefficient(D₃₃)of PVDF piezoelectric films with different SiO₂ dopants were studied.The electrometer was used to test the characteristics of charge accumulation on the surface of the film after charge neutralization,and to evaluate the electropole effect of piezoelectric PVDF film.(4)The piezoelectric film with sandwich structure was prepared by encapsulating the piezoelectric film with flexible polyester(PET)film with conductive copper foil.The piezoelectric signal was obtained through quasi-static press and dynamic cyclic loading,which confirmed the application prospect of composite piezoelectric film in flexible piezoelectric sensors.