Near-electric Field Direct Writing Preparation And Properties Of PVDF Piezoelectric Films

Polyvinylidene fluoride?PVDF?,as a piezoelectric polymer,has the advantages of high sensitivity,low density,and good flexibility compared with traditional piezoelectric ceramics.It is unique in the preparation of light,compact,flexible and bendable sensors,and is an ideal material for manufacturing wearable flexible sensors.The process of preparing the PVDF piezoelectric thin film by traditional methods requires high equipment,complicated process,low?phase of PVDF and large deviation between products.In this paper,the near-electric field direct writing method is used to prepare printing inks with different compositions.By changing the ink composition and the added content,various parameter conditions that affect the smooth printing in the preparation process are discussed.And in the experiment,the prepared PVDF was subjected to a constant temperature water bath for a certain period of time,and the effect of the water bath on the?-phase content,piezoelectricity and dielectric properties of the PVDF composite films were discussed.The dielectric and piezoelectric properties of PVDF piezoelectric films doped with nano-ZnO and ionic liquids and ZnO are also studied.Through the above research,the main conclusions are:?1?The PVDF printing solution prepared by adding TBAC is conducive to the smooth operation of the near-field direct writing method.Appropriate reduction in jet diameter accelerates the evaporation of 1-methyl-2-pyrrolidone?NMP?and other solvents,and can be written and dried during the film preparation.Compared with the traditional methods such as casting and spin coating,the introduction of TBAC in the near-electric field direct writing method increased the content of the?phase of the film?F????.Compared with 48.74%of the spin coating method and 75.46%of the casting method,F???can be 84.73%using the near-electric field direct writing method of adding 0.5wt%TBAC.?2?In the PVDF/[Emim]BF₄?IL?piezoelectric thin film prepared by the near electric-field direct writing method,the spherulite radius of the thin film is greatly reduced and the film density is increased.When the amount of[Emim]BF₄ added is 1.5wt%,the relative?phase content of the PVDF film reaches 85.09%,and the crystallinity is 45.69%.As the content of[Emim]BF₄ increases,the relative dielectric constant??'?increases from 6 to 285,and the piezoelectric constant(d₃₃)of the film arrives at-10pC/N.?3?After the PVDF/[Emim]BF₄ film was subjected to a constant temperature water bath at 70°C,while the?phase content remained unchanged,the high relative dielectric constant?'and the high loss tangent tan?dropped to a lower level,but still Pure PVDF films are several times taller.When the film sample with[Emim]BF₄ added in an amount of 1.5wt%was subjected to a constant temperature water bath,the d₃₃ value was maintained at a value of-10pC/N,and the output voltage could reach 886mV.?4?The addition of small amount of nano-ZnO is sufficient to rapidly increase the relative content of?phase in the film,but the crystallinity of the film has decreased to some extent.When the amount of ZnO added is 0.02wt%,the relative?phase content of the PVDF film can reach 88.92%,and the dielectric constant and piezoelectric constant of the PVDF/ZnO piezoelectric films are higher than those of the pure PVDF film.When the ZnO content is 0.03wt%,?'is 12.4 at 1kHz.The d₃₃ value of the film is up to-9pC/N,and the output voltage is increased to 351mV compared with pure PVDF film.?5?The blending of[Emim]BF₄ and ZnO inhibits the transformation of the?-phase crystal form of the PVDF film,so that the average d₃₃ of the PVDF/[Emim]BF₄/ZnO composite film is only-4pC/N and the output voltage is 157mV.