Speaker
Description
Introduction: To this date, Melt Electrowriting (MEW) is primarily done on flat collectors for tissue engineering (TE) applications. There are no flat geometries in the body, so it is crucial to find ways to fabricate out-of-plane scaffolds that better conform to the shape of the targeted tissues. 6-axis robots have been used in MEW to move the printhead around a static collector for the fabrication of corneal implants [1]. There were several challenges behind this strategy, such as inaccuracies due to the polymer jet not being parallel to the field of gravity, instabilities of the electrical field and lack of repeatability. These issues prevented accurate fiber deposition. We have explored a 5-axis approach where the movement is provided to the collecting platform to maintain orthogonality between the printhead and the surface of the collecting substrate. As an example of this kinematic strategy, here we explore the fabrication of out-of-plane corneal implants. The standard thickness of MEW scaffolds (25-35 microns) provides insufficient strength to hold sutures, so we also explored the hybridization of MEW with Fused Deposition Modeling (FDM) to produce reinforced implants with thicker FDM-fiber borders.
Methods: The cornea is often perceived to be semi-spherical, however, it is a highly personalized convex surface. In addition to accurately rendering a patient’s corneal shape, we wish to render pores with a small enough area that cells can fully spread across the boundary filaments (Fig. 1A). To accomplish these goals, we designed a MEW machine that features 5 axes of combined motion for the collector (XY, rotation around X and rotation around Z) and the printhead (Z) (Fig. 1B). For the fabrication of the corneal implant, Purasorb® PC 12 polycaprolactone pellets (Corbion, Netherlands) were melted for 1-hour prior to printing at 80°C and then extruded at a pressure of 0.33 Bar. The high voltage and translating speed of the collector were set to 5 kV and 22 mm/s, respectively. For the FDM borders, the extrusion rate and translating speed of the collector was adjusted so that a 0.4-mm thick fiber was printed. The toolpath design and postprocessing of G-Codes for both was done in Fusion 360 (Autodesk, California, US).
Results: Fig. 1C shows the out-of-plane corneal textile after printing, which contains the MEW layering of pores that will serve for cell attachment and proliferation. At the border of the textile, the thicker FDM fiber will serve as reinforcement for the retention of sutures.
Discussion: This work shows the fabrication process of personalized corneal implants using a novel multi-axis and hybrid automated approach. It also provides key aspects on MEW parameter optimization for out-of-plane printing and MEW and FDM compatible tooling design. Furthermore, we believe that this work will serve as an inspiration to the growing community of MEW enthusiasts to provide them with key insights that they can incorporate in their future work for the fabrication of scaffolds that are useful for TE applications.
References:
[1] Luposchainsky, S. et al. (2022). Melt Electrowriting of Poly(dioxanone) Filament Using a Multi‐Axis Robot.
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