@article{BoehmStahlhutWeichholdetal.2022,
  author    = {B{\"o}hm, Christoph and Stahlhut, Philipp and Weichhold, Jan and Hrynevich, Andrei and Teßmar, J{\"o}rg and Dalton, Paul D.},
  title     = {The Multiweek Thermal Stability of Medical-Grade Poly(ε-caprolactone) During Melt Electrowriting},
  series = {Small},
  volume    = {18},
  journal   = {Small},
  number    = {3},
  doi       = {10.1002/smll.202104193},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257741},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{HrynevichAchenbachJungstetal.2021,
  author    = {Hrynevich, Andrei and Achenbach, Pascal and Jungst, Tomasz and Brook, Gary A. and Dalton, Paul D.},
  title     = {Design of Suspended Melt Electrowritten Fiber Arrays for Schwann Cell Migration and Neurite Outgrowth},
  series = {Macromolecular Bioscience},
  volume    = {21},
  journal   = {Macromolecular Bioscience},
  number    = {7},
  doi       = {10.1002/mabi.202000439},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257535},
  year      = {2021},
  abstract  = {In this study, well-defined, 3D arrays of air-suspended melt electrowritten fibers are made from medical grade poly(ɛ-caprolactone) (PCL). Low processing temperatures, lower voltages, lower ambient temperature, increased collector distance, and high collector speeds all aid to direct-write suspended fibers that can span gaps of several millimeters between support structures. Such processing parameters are quantitatively determined using a "wedge-design" melt electrowritten test frame to identify the conditions that increase the suspension probability of long-distance fibers. All the measured parameters impact the probability that a fiber is suspended over multimillimeter distances. The height of the suspended fibers can be controlled by a concurrently fabricated fiber wall and the 3D suspended PCL fiber arrays investigated with early post-natal mouse dorsal root ganglion explants. The resulting Schwann cell and neurite outgrowth extends substantial distances by 21 d, following the orientation of the suspended fibers and the supporting walls, often generating circular whorls of high density Schwann cells between the suspended fibers. This research provides a design perspective and the fundamental parametric basis for suspending individual melt electrowritten fibers into a form that facilitates cell culture.},
  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}
}