Holistic investigation of the electrospinning parameters for high percentage of β-phase in PVDF nanofibers

Abstract

PVDF is a piezoelectric polymer that exists in five phases with the β-phase contributing the maximum to its piezoelectricity. Electrospinning is the most popular method used by researchers for developing PVDF nanofibers-based sensors. A holistic study pertaining to all the important electrospinning parameters is done in this paper to quantify their effects on the percentage of β-phase in the electrospun PVDF nanofibers. A new strategy to group the different electrospinning parameters based on their effect on various phases of the electrospinning process has been devised. Spin distance has been found to have the maximum effect with a variation of 6.6% on the percentage of β-phase in the PVDF nanofibers. The other parameters with a large effect on the percentage of β-phase are the electric field between needle and collector, the speed of the drum and the flow rate of the solution with variations of 6.3, 5.9 and 5.7% respectively. The group of parameters with the largest effect on the percentage of β-phase is the one directly affecting the stretching of the nanofibers (containing spin distance, drum speed and electric field) in the PVDF solution in the electrospinning process. A sensor has been developed with the use of the optimized parameters on a flexible LCP substrate. The voltage output of the sensor is studied for different electrospinning time (mat thicknesses) for a dynamic strain stimulus and is found to be maximum for sensor developed with 1 h of electrospinning. This is a systematic and comprehensive study that can be utilized for any electrospinning set-up for optimizing the properties of the nanofibers.