Establishment of Unique Cone Shapes and Universal Shape Parameters toward Predicting Fiber Diameter in Polymer Electrospinning

Abstract

Fiber diameter plays an important role in determining the performance of electrospun meshes in several applications. Since fiber diameter is known to be correlated to specific cone/jet features (e.g., cone height), real-time visualization of electrospinning can potentially facilitate direct control over fiber properties. However, progress in this direction has been hampered by a lack of objective criteria to accurately identify key cone/jet features, as well as a lack of shape parameters that can be applied across cone shapes. This study identifies unique cone shapes in electrospinning and establishes shape parameters that correlate with fiber diameter. Poly(caprolactone) was electrospun from two different solvents, and three unique cone shapes with different curvature signatures were identified from real-time visualization: convex−concave, pinned concave, and unpinned concave. An algorithm involving an iterative power law fit to the cone/jet boundary was developed, and inflection points in the exponents were used to identify universal shape parameters across all cone shapes: coneend (Lcf), jet-start (Lji), and corresponding diameters Dcf and Dji. Trends in shape parameters were validated as functions of voltage, flow rate, and solution concentration, and their predictive power was demonstrated by correlating Lcf and Lji with fiber diameter. The algorithm was also applied to a droplet-jet shape to determine the locations of Lcf and Lji, thus indicating its universality in identifying shape parameters. The process−property relationships developed herein apply across electrospinning parameters and cone shapes, and can be used to control fiber diameter in electrospinning.