Nanofibre fabrication in a temperature and humidity controlled environment for improved fibre consistency

Abstract

Fabricating nanofibres with reproducible characteristics is an important demand in the membrane industry in order to establish commercial viability. In this study, the effect of controlled atmospheric conditions on electrospun cellulose acetate (CA) nanofibres was evaluated for temperatures ranging 17.5-32.5°C and relative humidity ranging 20-70%. CA solution (0.2 g/mL) in a solvent mixture of acetone/dimethylformamide/ethanol (2:2:1) was electrospun into nonwoven fibre mesh with the fibre diameter ranging from 150 nm to 1 lm. The resulting nanofibres were analysed by differential scanning calorimetry, showing a correlation of reducing melt enthalpy with increasing atmospheric temperature. The opposite was seen with increasing atmospheric humidity, which conferred increasing melt enthalpy. Analysis of scanning electron microscopy images provided a correlation of reducing average fibre diameter with increasing atmospheric temperature and increasing fibre diameter with increasing atmospheric humidity. These results correlate with the melt enthalpy results, suggesting that finer CA nanofibres infer a lower melt enthalpy. Together these studies provide strong evidence that the controlled atmospheric conditions affect the fibre diameter of the resulting electrospun nanofibres. A salient observation in this study was that increased humidity reduced the effect of fibre beading yielding a more consistent and therefore better quality of fibre. This has apparent implications for the reproducibility of nanofibre production and offers a new method of controlling fibre morphology. This study has highlighted the requirement to control atmospheric conditions during the electrospinning process to fabricate reproducible fibre mats.

Effects of Humidity and Solution Viscosity on Electrospun Fiber Morphology

“…The effects of humidity on fiber morphology are poorly understood and/or there are contradictory effects that have been observed that appear to be dependent on properties such as the type of polymer, polymer-solvent combination, molecular weight, polymer hydrophilicity, and size of the electrospun structure. [62][63][64][65][66] Both the incomplete reporting of electrospinning conditions and the limited understanding of environmental effects on fiber formation make it difficult to predict and reproduce electrospun scaffold microarchitecture.…”

Electrospinning predictions using artificial neural networks

“…Whilst atmospheric conditions are known to contribute to fibre diameter and morphology, unless these conditions vary significantly from standard atmospheric conditions, the effects are minimal [32,50,60]. Additionally these parameters are often not quoted in the literature and are difficult to control with most laboratory setups.…”

Characterizing the Reproducibility of the Properties of Electrospun Poly(d,l-Lactide-Co-Glycolide) Scaffolds for Tissue-Engineered Blood Vessel Mimics

“…As discussed in Chapter 2, these environmental factors cannot be controlled in the current electrospinning setup; they are only monitored and recorded at the beginning of each spin. It has been shown in other studies that temperature and humidity affect the electrospinning process 64,65,81 . The environmental fluctuations therefore may have contributed to variability in fiber diameter.…”

“…Finally, environmental effects could have an impact on cone stability and subsequent variability of the scaffolds, as demonstrated in the literature 64,65,68,81 . An additional analysis that was performed with the preliminary data from this thesis also suggested that environment had an impact on fiber diameter.…”

“…Humidity varied considerably for several spins, which may have affected the variability of the scaffolds. Other studies have shown that temperature and humidity greatly affect the electrospinning process 64,65,81 . This will be discussed in greater detail later in this thesis.…”