Introduction

Melt electrowriting (MEW) is a polymer melt processing technique which involves formation of polymer fibres and their controlled deposition to create complex architectures following additive manufacturing (AM) principles. A high voltage (up to 10 kV) applied across the nozzle-collector gap (0 – 10 mm) leads to the formation of a Taylor cone at the tip of the nozzle which forms into a stable polymer jet. The electrical forces acting on the jet lead to its thinning as it travels from the nozzle to the collector and fibres in the range of 5 – 50 μm can be formed depending on the parameters used. Once a stable jet is formed, the nozzle can be moved with respect to the collector at pre-defined speeds to deposit fibres in controlled and layer-by-layer manner.

Working principle

Figure 1: Schematic showing the working principle of melt electrowriting (MEW).

State of the Art

At the moment, melt electrowriting has a wide degree of freedom:
Fibres can be placed in many ways creating different patterns such as sinusoidal or triangular structures. At LMIS1 we utilise a novel MEW platform based on an open source FDM printer. This allows us to configure the printer to our needs and incorporate novel ideas.  

Figure 2: left: Schematic showing the influence of different parameters on the resulting print (image taken from Florczak, et al. Melt Electrowriting of Electroactive Poly(Vinylidene Difluoride) Fibers. Polym. Int. 2019, 68 (4), 735. https://doi.org/10.1002/pi.5759), right: different fabricated patterns (top two images taken from Liashenko, et al. Designing Outside the Box: Unlocking the Geometric Freedom of Melt Electrowriting  using Microscale Layer Shifting. Adv. Mater. 2020, 32, 2001874. https://doi.org/10.1002/adma.202001874)

Tubular printing

While most printing in melt electrowriting focusses on planar collectors, tubular collectors have also been used for many years. At LMIS1, one of the printers is focused on tubular MEW with different materials and different novel geometries. 

Figure 3: CAD drawing of a printer with a tubular collector (left) and two different tubular scaffolds (right, scale bar = 2 mm).

For semester projects and possible master theses look here: https://www.epfl.ch/labs/lmis1/student-projects/ 

The MEWron project

We were involved in the development of the so-called MEWron, an open-source melt electrowriting machine based on the Voron 0.1 3D printer. The original work has been led by our colleagues at the University of Oregon and has since been published (>>HERE<<). The original source code can be found on GitHub (>>HERE<<). We have since made changes to the initial files and will upload them in GitHub soon. Here we will publish the full code for a tubular printer similar to the one previously reported by Reizabal et al. 

In our work we aim to adhere to this protocol when it comes to the publication of parameters.

Keywords: melt electrowriting, melt electrospinning writing, MEW