TY - JOUR A1 - Robinson, Thomas M. A1 - Hutmacher, Dietmar W. A1 - Dalton, Paul D. T1 - The next frontier in melt electrospinning: taming the jet JF - Advanced Functional Materials N2 - There is a specialized niche for the electrohydrodynamic jetting of melts, from biomedical products to filtration and soft matter applications. The next frontier includes optics, microfluidics, flexible electronic devices, and soft network composites in biomaterial science and soft robotics. The recent emphasis on reproducibly direct‐writing continual molten jets has enabled a spectrum of contemporary microscale 3D objects to be fabricated. One strong suit of melt processing is the capacity for the jet to solidify rapidly into a fiber, thus fixing a particular structure into position. The ability to direct‐write complex and multiscaled architectures and structures has greatly contributed to a large number of recent studies, explicitly, toward fiber–hydrogel composites and fugitive inks, and has expanded into several biomedical applications such as cartilage, skin, periosteum, and cardiovascular tissue engineering. Following the footsteps of a publication that summarized melt electrowriting literature up to 2015, the most recent literature from then until now is reviewed to provide a continuous and comprehensive timeline that demonstrates the latest advances as well as new perspectives for this emerging technology. KW - 3D printing KW - additive manufacturing KW - eletrhydrodynamic KW - melt electrospinning writing Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204819 VL - 29 ER - TY - JOUR A1 - Mieszczanek, Pawel A1 - Robinson, Thomas M. A1 - Dalton, Paul D. A1 - Hutmacher, Dietmar W. T1 - Convergence of Machine Vision and Melt Electrowriting JF - Advanced Materials N2 - Melt electrowriting (MEW) is a high-resolution additive manufacturing technology that balances multiple parametric variables to arrive at a stable fabrication process. The better understanding of this balance is underscored here using high-resolution camera vision of jet stability profiles in different electrical fields. Complementing this visual information are fiber-diameter measurements obtained at precise points, allowing the correlation to electrified jet properties. Two process signatures—the jet angle and for the first time, the Taylor cone area—are monitored and analyzed with a machine vision system, while SEM imaging for diameter measurement correlates real-time information. This information, in turn, allows the detection and correction of fiber pulsing for accurate jet placement on the collector, and the in-process assessment of the fiber diameter. Improved process control is used to successfully fabricate collapsible MEW tubes; structures that require exceptional accuracy and printing stability. Using a precise winding angle of 60° and 300 layers, the resulting 12 mm-thick tubular structures have elastic snap-through instabilities associated with mechanical metamaterials. This study provides a detailed analysis of the fiber pulsing occurrence in MEW and highlights the importance of real-time monitoring of the Taylor cone volume to better understand, control, and predict printing instabilities. KW - polycaprolactone KW - 3D printing KW - digitization KW - electrohydrodynamic KW - melt electrospinning writing Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256365 VL - 33 IS - 29 ER - TY - JOUR A1 - Liashenko, Ievgenii A1 - Hrynevich, Andrei A1 - Dalton, Paul D. T1 - Designing Outside the Box: Unlocking the Geometric Freedom of Melt Electrowriting using Microscale Layer Shifting JF - Advanced Materials N2 - Melt electrowriting, a high‐resolution additive manufacturing technology, has so far been developed with vertical stacking of fiber layers, with a printing trajectory that is constant for each layer. In this work, microscale layer shifting is introduced through deliberately offsetting the printing trajectory for each printed layer. Inaccuracies during the printing of sinusoidal walls are corrected via layer shifting, resulting in accurate control of their geometry and mechanical properties. Furthermore, more substantial layer shifting allows stacking of fiber layers in a horizontal manner, overcoming the electrostatic autofocusing effect that favors vertical layer stacking. Novel nonlinear geometries, such as overhangs, wall texturing and branching, and smooth and abrupt changes in printing trajectory are presented, demonstrating the flexibility of the layer shifting approach beyond the state‐of‐the‐art. The practice of microscale layer shifting for melt electrowriting enables more complex geometries that promise to have a profound impact on the development of products in a broad range of applications. KW - 3D printing KW - additive manufacturing KW - biomaterials KW - electrohydrodynamics KW - melt electrospinning writing Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-217974 VL - 32 IS - 28 ER - TY - JOUR A1 - Kade, Juliane C. A1 - Bakirci, Ezgi A1 - Tandon, Biranche A1 - Gorgol, Danila A1 - Mrlik, Miroslav A1 - Luxenhofer, Robert A1 - Dalton, Paul D. T1 - The Impact of Including Carbonyl Iron Particles on the Melt Electrowriting Process JF - Macromolecular Materials and Engineering N2 - Melt electrowriting, a high-resolution additive manufacturing technique, is used in this study to process a magnetic polymer-based blend for the first time. Carbonyl iron (CI) particles homogenously distribute into poly(vinylidene fluoride) (PVDF) melts to result in well-defined, highly porous structures or scaffolds comprised of fibers ranging from 30 to 50 µm in diameter. This study observes that CI particle incorporation is possible up to 30 wt% without nozzle clogging, albeit that the highest concentration results in heterogeneous fiber morphologies. In contrast, the direct writing of homogeneous PVDF fibers with up to 15 wt% CI is possible. The fibers can be readily displaced using magnets at concentrations of 1 wt% and above. Combined with good viability of L929 CC1 cells using Live/Dead imaging on scaffolds for all CI concentrations indicates that these formulations have potential for the usage in stimuli-responsive applications such as 4D printing. KW - additive manufacturing KW - melt electrospinning writing KW - magnetoactive materials KW - electroactive polymers Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318482 SN - 1438-7492 VL - 307 IS - 12 ER - TY - JOUR A1 - Fuchs, A. A1 - Youssef, A. A1 - Seher, A. A1 - Hochleitner, G. A1 - Dalton, P. D. A1 - Hartmann, S. A1 - Brands, R. C. A1 - Müller-Richter, U. D. A. A1 - Linz, C, T1 - Medical-grade polycaprolactone scaffolds made by melt electrospinning writing for oral bone regeneration – a pilot study in vitro JF - BMC Oral Health N2 - Background The spectrum of indications for the use of membranes and scaffolds in the field of oral and maxillofacial surgery includes, amongst others, guided bone regeneration (GBR). Currently available membrane systems face certain disadvantages such as difficult clinical handling, inconsistent degradation, undirected cell growth and a lack of stability that often complicate their application. Therefore, new membranes which can overcome these issues are of great interest in this field. Methods In this pilot study, we investigated polycaprolactone (PCL) scaffolds intended to enhance oral wound healing by means of melt electrospinning writing (MEW), which allowed for three-dimensional (3D) printing of micron scale fibers and very exact fiber placement. A singular set of box-shaped scaffolds of different sizes consisting of medical-grade PCL was examined and the scaffolds’ morphology was evaluated via scanning electron microscopy (SEM). Each prototype sample with box sizes of 225 μm, 300 μm, 375 μm, 450 μm and 500 μm was assessed for cytotoxicity and cell growth by seeding each scaffold with human osteoblast-like cell line MG63. Results All scaffolds demonstrated good cytocompatibility according to cell viability, protein concentration, and cell number. SEM analysis revealed an exact fiber placement of the MEW scaffolds and the growth of viable MG63 cells on them. For the examined box-shaped scaffolds with pore sizes between 225 μm and 500 μm, a preferred box size for initial osteoblast attachment could not be found. Conclusions These well-defined 3D scaffolds consisting of medical-grade materials optimized for cell attachment and cell growth hold the key to a promising new approach in GBR in oral and maxillofacial surgery. KW - melt electrospinning writing KW - polycaprolactone KW - scaffold KW - guided bone regeneration Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200274 VL - 19 ER - TY - JOUR A1 - Böhm, Christoph A1 - Tandon, Biranche A1 - Hrynevich, Andrei A1 - Teßmar, Jörg A1 - Dalton, Paul D. T1 - Processing of Poly(lactic–co–glycolic acid) Microfibers via Melt Electrowriting JF - Macromolecular Chemistry and Physics N2 - Polymers sensitive to thermal degradation include poly(lactic-co-glycolic acid) (PLGA), which is not yet processed via melt electrowriting (MEW). After an initial period of instability where mean fiber diameters increase from 20.56 to 27.37 µm in 3.5 h, processing stabilizes through to 24 h. The jet speed, determined using critical translation speed measurements, also reduces slightly in this 3.5 h period from 500 to 433 mm min\(^{−1}\) but generally remains constant. Acetyl triethyl citrate (ATEC) as an additive decreases the glass transition temperature of PLGA from 49 to 4 °C, and the printed ATEC/PLGA fibers exhibits elastomeric behavior upon handling. Fiber bundles tested in cyclic mechanical testing display increased elasticity with increasing ATEC concentration. The processing temperature of PLGA also reduces from 165 to 143 °C with increase in ATEC concentration. This initial window of unstable direct writing seen with neat PLGA can also be impacted through the addition of 10-wt% ATEC, producing fiber diameters of 14.13 ± 1.69 µm for the first 3.5 h of heating. The investigation shows that the initial changes to the PLGA direct-writing outcomes seen in the first 3.5 h are temporary and that longer times result in a more stable MEW process. KW - poly(lactide-co-glycolide) KW - 3D printing KW - additive manufacturing KW - electrohydrodynamics KW - melt electrospinning writing KW - plasticizers Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318444 VL - 223 IS - 5 ER - TY - JOUR A1 - Böhm, Christoph A1 - Stahlhut, Philipp A1 - Weichhold, Jan A1 - Hrynevich, Andrei A1 - Teßmar, Jörg A1 - Dalton, Paul D. T1 - The Multiweek Thermal Stability of Medical-Grade Poly(ε-caprolactone) During Melt Electrowriting JF - Small N2 - Melt electrowriting (MEW) is a high-resolution additive manufacturing technology that places unique constraints on the processing of thermally degradable polymers. With a single nozzle, MEW operates at low throughput and in this study, medical-grade poly(ε-caprolactone) (PCL) is heated for 25 d at three different temperatures (75, 85, and 95 °C), collecting daily samples. There is an initial increase in the fiber diameter and decrease in the jet speed over the first 5 d, then the MEW process remains stable for the 75 and 85 °C groups. When the collector speed is fixed to a value at least 10% above the jet speed, the diameter remains constant for 25 d at 75 °C and only increases with time for 85 and 95 °C. Fiber fusion at increased layer height is observed for 85 and 95 °C, while the surface morphology of single fibers remain similar for all temperatures. The properties of the prints are assessed with no observable changes in the degree of crystallinity or the Young's modulus, while the yield strength decreases in later phases only for 95 °C. After the initial 5-d period, the MEW processing of PCL at 75 °C is extraordinarily stable with overall fiber diameters averaging 13.5 ± 1.0 µm over the entire 25-d period. KW - polycaprolactone KW - 3D printing KW - additive manufacturing KW - electrohydrodynamic KW - melt electrospinning writing Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257741 VL - 18 IS - 3 ER -