Paul Dalton

Convergence of Machine Vision and Melt Electrowriting

Publisher: Wiley

Date: 08-06-2021

DOI: 10.1002/ADMA.202100519

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.

Hollow‐Fiber Melt Electrowriting Using a 3D‐Printed Coaxial Nozzle

Publisher: Wiley

Date: 02-08-2021

DOI: 10.1002/ADEM.202100750

Abstract: Herein, a 3D‐printed nozzle designed for the single‐step fabrication of melt electrowritten hollow fibers is introduced. To achieve this, selective laser melting (SLM) is used to fabricate the outer part of the coaxial nozzle (800 μm inner diameter) from Ti6Al4V, into which a conventional nozzle (250 μm inner diameter) is inserted. Several iterations of coaxial nozzle design result in a well‐aligned inner core nozzle that delivers air into the Taylor cone of medical‐grade poly(ε‐caprolactone) (PCL). Air from this bubble forms the hollow part of the fiber while the PCL shell solidifies as the shell. The smallest PCL fibers have an approximate outside diameter of 10 μm and a lumen of 6 μm, making this a promising one‐step technique for small diameter hollow fiber fabrication.

The Next Frontier in Melt Electrospinning: Taming the Jet

Publisher: Wiley

Date: 18-08-2019

DOI: 10.1002/ADFM.201904664

Printomics: the high-throughput analysis of printing parameters applied to melt electrowriting

Publisher: IOP Publishing

Date: 24-01-2019

DOI: 10.1088/1758-5090/AAFC41

Abstract: Melt electrowriting (MEW) combines the fundamental principles of electrospinning, a fibre forming technology, and 3D printing. The process, however, is highly complex and the quality of the fabricated structures strongly depends on the interplay of key printing parameter settings including processing temperature, applied voltage, collection speed, and applied pressure. These parameters act in unison, comprising the principal forces on the electrified jet: pushing the viscous polymer out of the nozzle and mechanically and electrostatically dragging it for deposition towards the collector. Although previous studies interpreted the underlying mechanism of electrospinning with polymer melts in a direct writing mode, contemporary devices used in laboratory environments lack the capability to collect large data reproducibly. Yet, a validated large data set is a condition sine qua non to design an in-process control system which allows to computer control the complexity of the MEW process. For this reason, we engineered an advanced automated MEW system with monitoring capabilities to specifically generate large, reproducible data volumes which allows the interpretation of complex process parameters. Additionally, the design of an innovative real-time MEW monitoring system identifies the main effects of the system parameters on the geometry of the fibre flight path. This enables, for the first time, the establishment of a comprehensive correlation between the input parameters and the geometry of a MEW jet. The study verifies the most stable process parameters for the highly reproducible fabrication of a medical-grade poly(ε-caprolactone) fibres and demonstrates how Printomics can be performed for the high throughput analysis of processing parameters for MEW.

Spatial Patterning of Hydrogels via 3D Covalent Transfer Stamping from a Fugitive Ink

Publisher: Wiley

Date: 24-11-2017

DOI: 10.1002/MARC.201700564

Abstract: In this study, a novel hydrogel patterning approach using 3D covalent transfer st ing from a fugitive ink is introduced. A model transfer molecule (7-diethylamino-3-(4'maleimidylphenyl)-4-methylcoumarin (CPM)) is absorbed into a 3D fugitive ink st made from poly(caprolactone), and then encapsulated in a poly(ethylene glycol) hydrogel. As the CPM diffuses from the fugitive ink to the curing hydrogel it is selectively covalently bound at the boundary of the ink and the hydrogel. Removal of the fugitive ink by solvent exchange leads to a negative copy of interconnected channels patterned with the localized transfer of the molecules at the hydrogel interface. The results suggest that small molecules can be patterned in porous hydrogels in a spatially controllable manner and that the transferred amount can be tuned.

Contributors

Publisher: Elsevier

Date: 2023

DOI: 10.1016/B978-0-12-824459-3.01002-7

Melt Electrowriting of Nylon‐12 Microfibers with an Open‐Source 3D Printer

Publisher: Wiley

Date: 24-10-2023

DOI: 10.1002/MARC.202300424

Melt electrowriting of electroactive poly(vinylidene difluoride) fibers

Publisher: Wiley

Date: 23-01-2019

DOI: 10.1002/PI.5759

Tailored Melt Electrowritten Scaffolds for the Generation of Sheet‐Like Tissue Constructs from Multicellular Spheroids

Publisher: Wiley

Date: 05-03-2019

DOI: 10.1002/ADHM.201801326

Abstract: Melt electrowriting (MEW) is an additive manufacturing technology that is recently used to fabricate voluminous scaffolds for biomedical applications. In this study, MEW is adapted for the seeding of multicellular spheroids, which permits the easy handling as a single sheet-like tissue-scaffold construct. Spheroids are made from adipose-derived stromal cells (ASCs). Poly(ε-caprolactone) is processed via MEW into scaffolds with box-structured pores, readily tailorable to spheroid size, using 13-15 µm diameter fibers. Two 7-8 µm diameter "catching fibers" near the bottom of the scaffold are threaded through each pore (360 and 380 µm) to prevent loss of spheroids during seeding. Cell viability remains high during the two week culture period, while the differentiation of ASCs into the adipogenic lineage is induced. Subsequent sectioning and staining of the spheroid-scaffold construct can be readily performed and accumulated lipid droplets are observed, while upregulation of molecular markers associated with successful differentiation is demonstrated. Tailoring MEW scaffolds with pores allows the simultaneous seeding of high numbers of spheroids at a time into a construct that can be handled in culture and may be readily transferred to other sites for use as implants or tissue models.

Tissue engineering of the nervous system

Publisher: Elsevier

Date: 2023

DOI: 10.1016/B978-0-12-824459-3.00017-2

University Of Oregon

Location: United States of America

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Julius-Maximilians-Universität Würzburg

Location: Germany

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Discovery Projects - Grant ID: DP230102934

Start Date: 2023

End Date: 12-2025

Amount: $449,148.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP110103890

Start Date: 2011

End Date: 12-2014

Amount: $500,000.00

Funder: Australian Research Council