Analysis of bending region physics in determining electrospun fiber diameter: effect of relative humidity on evaporation and force balance

This paper explores the role of the bending region and relative humidity (RH) in determining the resulting electrospun fiber diameter through a combined experimental and modeling analysis. Analysis of experimental measurements on PEO/water and PVP/alcohol solutions indicates that the bending region is significant in determining the final fiber diameter. A model is developed, to determine the dominant process physics of the bending region, predicting the final fiber diameter to be within 6% of experimental observations. The experimental analysis reveals that stretching in the bending region accounts for 40-60% of the stretching in the electrospinning process and the significant impact that RH has on fiber diameters. Our modeling analysis reveals the role of both evaporation and stretching in the bending region, and how RH influences both the jet length (stretching time) and force balance to determine the final fiber diameter.