LAUSR

Abstract The prominent success of polycaprolactone (PCL) bioengineered fibrous scaffolds has expanded the use of PCL over other polymers in the wide electrospinning literature. Several highly toxic solvent systems providing a good PCL solubility-spinability are recurrently applied in the overwhelming majority of studies. One of the current major focuses revolves around the challenging generation of aligned fibers that are very desirable in numerous tissue engineering applications. Moreover, the critical influence of fiber size on cellular performance has led to the use of different solvent systems for the production of specific nano- or micro-sized PCL fibers while neglecting the solvents toxicity. Therefore, our goal is to use the unconventional solvent system acetic acid/formic acid of very low toxicity, recently defined as the system producing ultra-thin PCL fibers, in a trial to outspread the size range and to tackle fiber alignment. After profound analysis of the effect of varying collector motion and collector design on fiber alignment, a novel collector producing highly aligned PCL fibers based on synchronic mechanical and electrical effects is designed. In a subsequent step, the fiber diameter is manipulated by analyzing 3 influential parameters: polymer concentration, tip-to-collector distance and the frequently overlooked parameter humidity. The parameters fine-tuning study has resulted in very broad PCL fiber diameter ranges of 94–1548 nm and 114–1408 nm for random and aligned fibers respectively. PCL fibers properties are also characterized in this study by means of water contact angle (WCA), X-ray photoelectron spectroscopy (XPS) and tensile measurements. Despite the detection of the same surface chemical composition on all fiber conditions, the WCA values tend to decrease with increased fiber diameters, especially for aligned fibers. Moreover, aligning the fibers and decreasing their size is found to lead to considerably enhanced mechanical properties. Overall, it can be concluded that this work represents a picture-perfect reference for the electrospinning of PCL fibers having different orientations, diameters and physico-chemical properties from a benign solvent system.