(C-81) Revolutionizing Biomedical Research: High-resolution scaffold fabrication via an open-source melt electrowriting platform

Introduction:: Melt electrowriting (MEW) is a new method of additive manufacturing (commonly termed 3D printing) that utilizes a high voltage potential and an electrically charged molten polymer to fabricate porous and high-resolution structures. While more conventional 3D printing methods such as fused filament fabrication (FFF) and stereolithography (SLA) produce features ranging from 30 to 200 micrometers, MEW can produce fibers ranging from 0.5 to 50 micrometers in diameter. High-resolution MEW scaffolds have been used primarily in fields such as tissue engineering, cancer research, biofabrication, and biomaterials, but have potential applications in many other areas.

The majority of MEW research has been conducted on custom systems, which are difficult to reproduce and standardize, or commercial off-the-shelf printers, which are complex and unaffordable. The MEWron project developed a process of modifying the Voron 0.1, an existing open-source FFF printer, to perform MEW. One configuration of the MEWron allows for MEW with a standard molten polymer syringe, while another allows for printing with more readily available polymer filament. Excluding the high voltage supply necessary for MEW, this system costs less than $1,000.The MEWron's open-source design, affordability, and versatility in printing materials significantly enhance accessibility and applicability of MEW across research and industries, with a profound impact in the field of biomedical engineering.


Materials and Methods:: The first step in building a functional MEWron is assembling a well-calibrated and functional FFF Voron. The open-source Voron 0.1 printer was selected for this conversion due to its affordability, printing quality, and significant community-based support. This Voron is also small, has core XY kinematics, and independent Z collector control, allowing for more precision at the higher printing speeds required for MEW.

Two versions of the MEWron have been developed (Figure 1); the first is a syringe MEWron, which uses an aluminum block to hold and heat a glass syringe of molten polymer and an external pressure supply to control flow rate. The second is a filament MEWron, which uses the Voron's original filament printhead setup but with a higher resolution stepper motor to allow for the lower flow rates required for MEW. In both versions the heaters and thermistors are electrically insulated with ceramic tubing in case of any arcing during printing.

Both versions of the MEWron require the same modified z-axis collector, which is designed to generate the required high voltage potential while being insulated from conductive and electrical elements of the printer. To do this, the original z-axis collector was replaced with a borosilicate glass plate, with the original heater and thermistor on the bottom side and the magnetic pad and steel plate on the top. A wire for high voltage is secured to the build plate assembly via a FFF printed part and the charge is transmitted to the printing plate through a pogo pin.


Results, Conclusions, and Discussions:: The functionality and suitability of the MEWron was evaluated by testing its safety and ability to print high-resolution scaffolds with the precise control enabled by larger commercial and custom systems. Electrical safety was verified by applying 10 kV, higher than the working voltage range for MEW of 4-5 kV, to the build plate and seeing no electrical discharge from charged surfaces. Furthermore, a high voltage was applied while running the printer, and the distance between the printhead and the collector was decreased until there was electrical discharge. The electronics remained fully functional following the arc, verifying the effectiveness of the insulated components in the system.

Unlike traditional MEW printers that use precise screw driven linear rails to control fiber placement, the Voron 0.1 uses two stepper motors and a belt driven system to position the printhead. To verify the microstepping control and repeatability of MEWron scaffolds, identical scaffolds were printed on two separate MEWron printers (syringe and filament). Poly(ε-caprolactone) (PCL) was used in these validation scaffolds as it is the gold standard polymer for MEW due to its low melting point and thermal stability. Both printers were able to produce homogeneous fibers, accurate pores, and precise vertical stacking. The two resultant scaffolds were also very similar.

Another feature of the filament MEWron specifically is the ability to dynamically control the flow rate by manipulating the extrusion stepper motor in the G-Code programs. This unique ability was demonstrated by printing a scaffold with an extruded layer similar to those found in FFF followed by a MEW layer, with a continuous voltage applied. Additionally, filament driven MEW enables printing of materials with lower thermal stability, as they are held above their melting point for shorter amounts of time than in standard syringe systems.

The ability to print materials with higher melting points that undergo thermal degradation closer to those temperatures was proven by printing high-quality polylactic acid (PLA) scaffolds with both the syringe and filament MEWrons. Further experiments explored printing of thermoplastic polyurethane (TPU), and the produced high-quality scaffolds demonstrate the MEWron’s potential in exploring new polymers for MEW.


Acknowledgements (Optional): : Startup funding from the Phil and Penny Knight Campus for Accelerating Scientific Impact is greatly appreciated. The support of the Wu Tsai Human Performance Alliance and the Joe and Clara Tsai Foundation is appreciated. Paula G. Saiz thanks the University of the Basque Country (UPV/EHU) for the Margarita Salas postdoctoral grant financed by the European Union – Next generation EU.

References (Optional): : Ander Reizabal, Taavet Kangur, Paula G. Saiz, Sönke Menke, Christophe Moser, Jürgen Brugger, Paul D. Dalton, Simon Luposchainsky, MEWron: An open-source melt electrowriting platform, Additive Manufacturing, Volume 71, 2023, 103604, ISSN 2214-8604, https://doi.org/10.1016/j.addma.2023.103604.