Preparation Of PEDOT:PSS/PVDF Composite Force Sensing Material

The performance of a flexible force sensor mainly depends on its sensing material and device structure,among which the sensing property of the sensing material is the most important factor.Piezoelectric pressure sensing material consists of piezoelectric layer and electrode layers that collect and conduct piezoelectric signal.Generally,the electrodes are made of metals,which have many disadvantages,including high density,poor bendability,and high processing cost.Therefore,we consider using conductive polymer material poly（3,4-ethylenedioxythiophene）:poly（styrenesulfonate）（PEDOT:PSS）instead of metal to prepare electrodes and combining it with piezoelectric polymer poly（vinylidene fluoride）（PVDF）to prepare a flexible pressure force sensing composite.In this paper,chemical oxidative synthesis was used to prepare processable PEDOT:PSS suspension.Vacuum filtration was used to prepare conductive PEDOT:PSS film.Electrospinning was applied to prepare PVDF film with highβ-phase content.PEDOT:PSS electrode was deposited on the PVDF piezoelectric film via vacuum filtration and finally sandwiched to be the PEDOT:PSS/PVDF pressure sensing composite.The main research work is as follows:1.The amount of oxidant（NH₄）₂S₂O₈ in the chemical oxidative synthesis method would affect the conductivity of the PEDOT:PSS film.Products prepared using a series of oxidant amount were investigated.The highest film conductivity of 19.19 S/cm was obtained when the molar ratio of（NH₄）₂S₂O₈∶EDOT was 0.875.2.Solvent treatment with DMAc,NMP or DMSO could improve the conductivity of PEDOT:PSS,of which DMSO showed the profound effect（167.27 S/cm）.3.The humidity condition of PVDF electrospinning had an effect on the film area.An increase in humidity led to smaller film area.The volume ratio of DMF∶acetone in spinning solution would affect the fiber morphology andβ-phase content.As this ratio was increased,the fiber diameter became smaller and more uneven.Theβ-phase content increased first and then decreased.The volume ratio of DMF:acetone from 7∶3 to 8∶2 is the optimal range in which the film had a good morphology and high content ofβ-phase crystal（79%to 81%）.3.The prepared PEDOT:PSS/PVDF composite had a pressure-sensitive response.The output voltage was 0.6⁰.8 V under the pressing of a knuckle with a short response time of around 0.25 s.Although its sensitivity needed to be improved,it confirmed the feasibility of the new method to prepare PEDOT:PSS/PVDF pressure force sensing composite.