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

MEW employs a continuous fibre jet, generated by an electric field that shapes the jet from a polymer melt. By manipulating the collector, the fibre is precisely deposited to form scaffolds. Our research introduces an innovative filament-based feeding system, which contrasts with the traditional pressure-driven syringe approach.

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.