Melt electrowriting (MEW) technique is a manufacturing technology used to fabricate scaffold with user-oriented design. Main distinctive compared to additive manufacturing technique is its ability to fabricate the diameter of few micrometers to sub micrometers range while maintaining high surface to volume ratio. However, this technique has certain drawbacks, such as inaccurate large volume scaffold and fiber placement, sagging and fiber pulsing behavior, and thermal damage to the material properties.
We introduce a controlled way of modulating fiber formation in MEW by optimized installation of a second heater in the vicinity of the Taylor cone, thus presenting additional processing parameters that help to tune the scaffold design parameters more robustly and mitigate some of the current drawbacks of this technique. The primary function of the second heater is to control the solidification rate of the polymer by increasing the ambient temperature surrounding the nozzle. The study is divided into four different sections. 1) Non-isothermal modelling and simulation using COMSOL are performed to optimize the location of the second heater to the nozzle axis and predict the temperature distribution along the spin line region with varying second heater temperatures. 2) Critical speed and fibre pulsing under different conditions are analyzed to evaluate the effect of the second heater on jet stability. 3) Mechanical testing of the stacked fibres is characterized to model/predict the fusion between layers under different conditions adn at last 4) Spinning of thermosensitive and high molecular weigth polymers are investigated, with a low syringe temperature to mitigate degradation and increasing spin line temperature to facilitate processing.
Overall, with the help of the second heater, we were able to fabricate scaffolds from a high molecular weight medical-grade polycaprolactone, poly L-lactide and PVDF, thus expanding the range of materials processable by this exciting technology.