@article{LoebleinLorsonKommaetal.2021,
  author    = {L{\"o}blein, Jochen and Lorson, Thomas and Komma, Miriam and Kielholz, Tobias and Windbergs, Maike and Dalton, Paul D. and Luxenhofer, Robert},
  title     = {An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)},
  series = {Beilstein Journal of Organic Chemistry},
  volume    = {17},
  journal   = {Beilstein Journal of Organic Chemistry},
  doi       = {10.3762/bjoc.17.136},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-369433},
  pages     = {2095-2101},
  year      = {2021},
  abstract  = {Additive manufacturing or 3D printing as an umbrella term for various materials processing methods has distinct advantages over many other processing methods, including the ability to generate highly complex shapes and designs. However, the performance of any produced part not only depends on the material used and its shape, but is also critically dependent on its surface properties. Important features, such as wetting or fouling, critically depend mainly on the immediate surface energy. To gain control over the surface chemistry post-processing modifications are generally necessary, since it′s not a feature of additive manufacturing. Here, we report on the use of initiator and catalyst-free photografting and photopolymerization for the hydrophilic modification of microfiber scaffolds obtained from hydrophobic medical-grade poly(ε-caprolactone) via melt-electrowriting. Contact angle measurements and Raman spectroscopy confirms the formation of a more hydrophilic coating of poly(2-hydroxyethyl methacrylate). Apart from surface modification, we also observe bulk polymerization, which is expected for this method, and currently limits the controllability of this procedure.},
  language  = {en}
}
@article{KadeTandonWeichholdetal.2021,
  author    = {Kade, Juliane C. and Tandon, Biranche and Weichhold, Jan and Pisignano, Dario and Persano, Luana and Luxenhofer, Robert and Dalton, Paul D.},
  title     = {Melt electrowriting of poly(vinylidene fluoride-co-trifluoroethylene)},
  series = {Polymer International},
  volume    = {70},
  journal   = {Polymer International},
  number    = {12},
  doi       = {10.1002/pi.6272},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257654},
  pages     = {1725-1732},
  year      = {2021},
  abstract  = {Poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-co-TrFE)) is an electroactive polymer with growing interest for applications in biomedical materials and flexible electronics. In this study, a solvent-free additive manufacturing technique called melt electrowriting (MEW) has been utilized to fabricate well-defined microperiodic structures of the copolymer (P(VDF-co-TrFE)). MEW of the highly viscous polymer melt was initiated using a heated collector at temperatures above 120 °C and required remarkably slow collector speeds below 100 mm min\(^{-1}\). The fiber surface morphology was affected by the collector speed and an increase in β-phase was observed for scaffolds compared to the unprocessed powder. Videography shows vibrations of the P(VDF-co-TrFE) jet previously unseen during MEW, probably due to repeated charge buildup and discharge. Furthermore, piezo-force microscopy measurements demonstrated the electromechanical response of MEW-fabricated fibers. This research therefore achieves the melt electrohydrodynamic processing of fibers with micrometer resolution into defined structures with an important electroactive polymer.},
  language  = {en}
}
@article{KadeOttoLuxenhoferetal.2021,
  author    = {Kade, Juliane C. and Otto, Paul F. and Luxenhofer, Robert and Dalton, Paul D.},
  title     = {Melt electrowriting of poly(vinylidene difluoride) using a heated collector},
  series = {Polymers for Advanced Technologies},
  volume    = {32},
  journal   = {Polymers for Advanced Technologies},
  number    = {12},
  issn      = {1042-7147},
  doi       = {10.1002/pat.5463},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318493},
  pages     = {4951 -- 4955},
  year      = {2021},
  abstract  = {Previous research on the melt electrowriting (MEW) of poly(vinylidene difluoride) (PVDF) resulted in electroactive fibers, however, printing more than five layers is challenging. Here, we investigate the influence of a heated collector to adjust the solidification rate of the PVDF jet so that it adheres sufficiently to each layer. A collector temperature of 110°C is required to improve fiber processing, resulting in a total of 20 fiber layers. For higher temperatures and higher layers, an interesting phenomenon occurred, where the intersection points of the fibers coalesced into periodic spheres of diameter 206 ± 52 μm (26G, 150°C collector temperature, 2000 mm/min, 10 layers in x- and y-direction).The heated collector is an important component of a MEW printer that allows polymers with a high melting point to be processable with increased layers.},
  language  = {en}
}
@article{KadeBakirciTandonetal.2022,
  author    = {Kade, Juliane C. and Bakirci, Ezgi and Tandon, Biranche and Gorgol, Danila and Mrlik, Miroslav and Luxenhofer, Robert and Dalton, Paul D.},
  title     = {The Impact of Including Carbonyl Iron Particles on the Melt Electrowriting Process},
  series = {Macromolecular Materials and Engineering},
  volume    = {307},
  journal   = {Macromolecular Materials and Engineering},
  number    = {12},
  issn      = {1438-7492},
  doi       = {10.1002/mame.202200478},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318482},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}