Electrostatic Distortion of Melt‐Electrowritten Patterns by 3D Objects: Quantification, Modeling, and Toolpath Correction

Abstract

Melt electrowriting (MEW) is an electrohydrodynamic process capable of producing organized patterns of micrometer‐scale polymer fibers. Integrating MEW with other additive manufacturing technologies, such as extrusion‐printing or bioprinting, offers tantalizing possibilities for multi‐scale biofabrication of anatomically shaped scaffolds. However, introducing 3D structures onto the conventionally flat collector plate significantly complicates the MEW process because these objects perturb the electrostatic field. Here, the systematic investigation of how simple 3D objects (hemispheres) distort MEW patterns printed in their vicinity is reported. The authors assess the influence of a series of parameters on fiber deflection including: distance from the hemisphere, hemisphere size and material composition, height of the nozzle, translation speed, applied voltage, and applied pressure. In light of these data, a model which captures the basic physics behind the deflection phenomenon is derived. An optimization algorithm to calculate tool‐paths which pre‐emptively account for these deviations is also introduced. Finally, the authors validate how G‐code produced by this algorithm effectively corrects the distortion effect, restoring the ability to create well‐defined MEW patterns in the vicinity of 3D objects. This study suggests a foundation for understanding the complexities of MEW on non‐planar collectors, and towards multitechnology biofabrication.

3D Plotting of Calcium Phosphate Cement and Melt Electrowriting of Polycaprolactone Microfibers in One Scaffold: A Hybrid Additive Manufacturing Process

“…Only when taking into account all printing parameters (nozzle-bed distance, pressure, E-field, moving velocity), can a balance be established between the material reservoir at the nozzle tip and the deposited volume, required to ensure a constant fiber diameter. In contrast, an inhomogeneous E-field implies local differences of the field strength, which can attract or deflect the fiber from its prescribed path [ 35 ]. This leads to variations in the lag of the fiber and thus in the elongation process (so-called fiber pulsing) [ 40 ] resulting in varying fiber diameters.…”

“…The combination of MEW and extrusion printing in an alternating setup is challenging as the MEW process requires a homogenous electrical field (E-field) for exact fiber deposition, this is significantly deteriorated when objectives, e.g., CPC strands, are present and create an inhomogeneous E-field [ 35 ]. In previous works, MEW-PCL fibers and CPC were combined when modeling tissue transitions, such as periodontal tissue [ 36 ] and the cartilage-bone boundary [ 37 ].…”

Recent advances in melt electro writing for tissue engineering for 3D printing of microporous scaffolds for tissue engineering

“…The fiber deflection in such printing conditions is usually material-independent but it is influenced by the distance to the object and the surface area of the object and the collector distance. Materials only then impact this process, when their charge relaxation times are shorter than the printing times ( O'Connell et al, 2021 ).…”

3D Printed Multiphasic Scaffolds for Osteochondral Repair: Challenges and Opportunities

“…Furthermore, ES is a solvent-based technique that randomly deposits lines of material onto the collector bed; whereas MEW is a solventfree approach that controls where and how the fibers are deposited, therefore providing control over the resulting pattern [162]. For MEW and ES, the material choice is driven by those that are processible following the electrohydrodynamic principles that guide both techniques [163,164]. PCL remains the most widely used material for MEW, while a broader range of materials, including PCL, gelation, chitosan, polyvinyl alcohol (PVA), HA and collagen are incorporated in ES [106,163,165,166].…”

“…A challenge when applying MEW and ES to OC scaffolds is in creating tall 3D structures as a charge builds-up which limits the ability to have a stable jet of material in the Z direction [169,170]. This limitation, has been addressed to increase the height of produced structures by printing onto various collector beds and objects [164,169,171].…”