Piezoelectric Performance Of Electrospun Polyvinylidene Fluoride Fibrous Membrane

Compared with the traditional piezoelectric materials, Poly(vinylidene fluoride)(PVDF)has been extensively studied as a new type of intelligent sensors because of its lightweight, goodflexibility, wide frequency response, high sensitivity of power electrical conversion and impactresistance. PVDF piezoelectric membrane fabricated by solution cast methods has high hardnessand poor air permeability, and the processing process is complex and high-cost. In contrast, PVDFfiber membrane fabricated by electrospinning is soft, lightweight and good air permeability, whichis an ideal choice for wearable product. In addition, the electrospinning method is simple,convenient and low-cost. However, it is lack of the characterization and test methods to study thepiezoelectric properties of electrospun PVDF fiber membrane, which restricts its furtherdevelopment and application. In this study, the above-mentioned problems are researched anddiscussed, and the solution is given.In this study, PVDF piezoelectric sensor is made of electrospun PVDF fiber membrane. Andthe piezoelectric properties of electrospun PVDF piezoelectric sensor are analyzed by thehome-made testing apparatus. The aim is to provide the foundation for the development ofintelligent textiles and wearable piezoelectric sensor equipment. The main works are as follows.(1) Fabrication and characterization of electrospun PVDF piezoelectric membrane. Firstly,electrospun PVDF fibers are received by the cylindrical receiving device to fabricate electrospunPVDF fiber membrane. In order to obtain the optimum parameters of electrospinning process, it isresearched that the parameters of electrospinning process and solution properties impact onmorphology and fiber diameter of PVDF fiber membrane by SEM and diameter analysis. Thencrystal structure transformation of electrospun PVDF fiber membrane is analyzed by XRD. Finally,electrospun PVDF piezoelectric membrane is fabricated with the optimum parameters.(2) Construct the testing apparatus of piezoelectric properties. Currently, there is no specifictesting apparatus for piezoelectric properties. A home-made testing apparatus of piezoelectricproperties is developed according to the output principle of PVDF piezoelectric sensor. It includescylindrical voice coil motor, clamping apparatus, pressure sensor, electrochemical workstation and other accessories. Cylindrical voice coil motor acts as the pressure device, the pressure sensor andelectrochemical workstation respectively detect pressure signal and voltage signal, and theclamping apparatus is used to fix the pressure sensor and electrospun PVDF piezoelectric sensor.(3) Test the piezoelectric properties of electrospun PVDF piezoelectric membrane. At first,PVDF piezoelectric sensor is made of electrospun PVDF fiber membrane. Then the piezoelectricproperties are discussed and analyzed from aspects of amplitude-frequency character, sensitivityand reproducibility.The experimental conclusions show that (1) The optimum parameters of electrospun PVDFfiber membrane are as fellows. Solution concentration is10%, the ratio of DMF/acetone is60:40by volume, the applied voltage is16kv, the feeding rate is1.0ml/h, the distance between theneedle tip and collector is15cm. Compared with PVDF powder and PVDF cast film, electrospunPVDF fiber membrane has a higher content of β phase. Electrospinning can achieve stretching andhigh voltage poling simultaneously, which is regarded as an ideal way to fabricate PVDF fibermembrane with β-phase formation.(2) The home-made testing apparatus of piezoelectricproperties can not only effectively regulate the change of pressure and frequency, but alsosimultaneously detect the pressure signal and the voltage signal, which can be used to analyze andstudy piezoelectric properties effectively.(3) The piezoelectric properties of electrospun PVDFpiezoelectric sensor are related to excitation frequency and excitation stroke under the cyclicalpressure. However, the response of sensor is insensitive to the low frequency but sensitive to thehigh-frequency, so it is more suitable for monitoring the high-frequency signal. When theexcitation stroke ranges from0.4mm to1.0mm, the maximum sensitivity can be up to380mv/mm. Meanwhile, electrospun PVDF piezoelectric sensor has a good reproducibility and cansteadily work for a long time.