@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{MieszczanekRobinsonDaltonetal.2021,
  author    = {Mieszczanek, Pawel and Robinson, Thomas M. and Dalton, Paul D. and Hutmacher, Dietmar W.},
  title     = {Convergence of Machine Vision and Melt Electrowriting},
  series = {Advanced Materials},
  volume    = {33},
  journal   = {Advanced Materials},
  number    = {29},
  doi       = {10.1002/adma.202100519},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256365},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}