Accumulated surface on stationary target: A new approach in electrospinning jet bending instability studies

Bending instability is a significant reason for the success of the electrospinning process for decreasing the fiber’s diameter to nanometer scales and a determining factor in final fiber morphology. Observation of electrospinning of different polymers revealed that electrospun fibers accumulate in a circular area with various diameters in the case of a stationary flat plate target. There is an idea that the diameter of accumulated surface (ASD) is controlled by bending instability, and there is a correlation between electrospun fiber diameter and ASD. In this study, the accumulation behaviors of Polystyrene (PS), Polymethyl methacrylate (PMMA), and coaxially electrospun fibers of PS-PMMA were evaluated concerning their ASD sizes, the rate of ASD’s growth, and the correlation between ADS size and the final diameters. To determine the role of processing parameters on this behavior and the relationship between the ASD and final fiber diameter, some experiments were designed for three factors of voltage, flow rate, and tip to target distance for electrospun fiber diameters and ASD in PMMA electrospinning. Two polynomial equations were found (via regression). Then, the polynomial models statistically were analyzed and discussed. Scanning electron microscopy (SEM) and fluorescent microscopy were applied for morphological studies, and Image J were used for measuring the sizes. The results demonstrated that during the electrospinning, the ASD grew with the natural logarithm of time and so ended to a plateau (specific diameter), and after that, the upcoming electrospun fibers accumulated on the former ones. Moreover, bigger ASDs were accompanied by smaller electrospun fiber diameters.