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3D Printed Polymer Blends Fabricated using Grayscale Digital Light Processing

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Digital light processing (DLP) 3D printing is used as an additive manufacturing method for its high-resolution and fast throughput capabilities to form complex shapes using photopolymers. However, restricted control over printed material properties has limited the technique. This presentation will explain an approach to design, manufacture and characterize composite polymer structures using grayscale DLP. In this approach, an initial part is printed using a custom DLP printer with a 405-nm LED projection system and a spatial light modulator to fabricate a part. Spatially modulating the intensity of the irradiated light onto the precursor resin using gray-scaling allows for volumetric control over material crosslinking density in this fabricated part. A secondary monomer is preferentially in-swollen to areas of low crosslinking density and polymerized to effectively fabricate a 3D-printed two-polymer composite using a facile single printing step while maintaining print fidelity. We utilize a linear thermoplastic polymer, otherwise not printable using DLP, for the second material. A deterministic model for polymer conversion in the printing process is utilized to inform printing conditions such that final composite properties can be predicted. This model is validated using confocal Raman microscopy to independently resolve the local concentration of the two-polymer systems throughout the composite using spectroscopy. Preliminary results of reducing layering effects, controlling local conversion using grayscale printing and forming two-material composites are demonstrated using this approach.

Learning Objectives:

  • Understand material properties in DLP printed parts as a function of exposure conditions and material properties, including polymerization rate and absorptivity
  • Recognize suitable material systems for fabricating composites using DLP
  • Develop a strategy to print a composites using DLP and validate print quality at the molecular scale using confocal Raman microscopy
  • John Hergert
    Graduate Research Assistant
    University of Colorado, Boulder