Research ArticleENGINEERING

Rapid, continuous additive manufacturing by volumetric polymerization inhibition patterning

See allHide authors and affiliations

Science Advances  11 Jan 2019:
Vol. 5, no. 1, eaau8723
DOI: 10.1126/sciadv.aau8723
  • Fig. 1 Concurrent, two-color photoinitiation and photoinhibition.

    (A) Optical setup for two-color SLA by concurrent photopolymerization and photoinhibition. Near UV (365 nm) is superimposed onto patterned blue (458 nm) with a dichroic mirror and projected through a transparent window into a photopolymerizable resin vat. Structures of (B) photoinitiator CQ, (C) co-initiator EDAB, and (D) photoinhibitor o-Cl-HABI. (E) UV-visible spectra of CQ (solid blue line) and o-Cl-HABI (dashed violet line) in tetrahydrofuran (THF). The UV and blue wavelengths used by the two-color AM system are highlighted by the violet and blue vertical bars, respectively. (F) Solid block M (left) and tug boat [model detailed in (31)] (right) printed using the two-color photopolymerization/photoinhibition stereolithography system at 500 and 375 mm/hour, respectively. (G) The polymerization inhibition volume thickness is affected by varying intensity ratios of the incident irradiation wavelengths (IUV,0/Iblue,0) and resin absorbance (hUV).

  • Fig. 2 Rapid, continuous AM with two-color photoinitiation and photoinhibition.

    (A) Argyle models printed using photoinhibition to enable continuous printing, with the percentage void (φ) and volume of the printed part (Vp) relative to the designed part (Vdes) shown below each part. The designed void was φ = 57%. (B) Cured thickness versus dosage of blue light for four acrylate-based resin formulations prepared with varying blue-absorbing dye (Epolight 5675) loadings. (C) Maximum vertical print speeds achievable for varying blue absorbance heights. All printing was done with Iblue,0 of 110 mW/cm2 and IUV,0 of 130 mW/cm2, with hUV of 125 μm. The influence of varying hUV, and hence inhibition volume thickness, on the predicted maximum achievable print speed, as determined by Eq. 2, is shown as solid lines.

  • Fig. 3 Wavelength-selective photoinitiation and photoinhibition of radical-mediated, chain-growth photopolymerization.

    Monomers examined include (A) bisphenol A ethoxylate diacrylate (BPAEDA; n = 4), (B) triethylene glycol dimethacrylate (TEGDMA), (C) bisphenol A glycerolate dimethacrylate (bisGMA), (D) triethylene glycol divinyl ether (TEGDVE), and (E) N-(n-propyl)maleimide (NPM). Alkene conversion versus time for resin formulations of (F) BPAEDA, (G) bisGMA/TEGDMA, and (H) TEGDVE/NPM (vinyl ether and maleimide conversions denoted by solid and dashed lines, respectively) under continuous irradiation with exclusively 470 nm @ 100 mW/cm2 (black line, squares), 470 nm @ 100 mW/cm2 and 365 nm @ 30 mW/cm2, (red line, circles), and 365 nm @ 30 mW/cm2 (blue line, diamonds).

  • Fig. 4 Two-color photoinitiation and photoinhibition enable controllable, far-surface patterning of complex 3D structures.

    (A) Setup used for intensity-patterned printing. (B) Use of variable intensity images enables pixel-wise adjustment of IUV,0/Iblue,0, producing variation in inhibition height and, therefore, printed part topography. (C) Four-level intensity image of the University of Michigan seal. (D) Variable thickness part produced by a single intensity-patterned exposure.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/1/eaau8723/DC1

    Supplement 1: Derivation of Eq. 1

    Supplement 2: Derivation of Eq. 2

    Fig. S1. Wavelength-selective photoinitiation and transient photoinhibition of methacrylate polymerization.

    Fig. S2. Effect of incident UV and blue illumination intensities on inhibition volume thickness and polymerization rate.

    Fig. S3. UV-vis spectra of UV and blue light absorbers.

    Fig. S4. Influence of co-initiator on o-Cl-HABI photoinitiation.

    Fig. S5. LabVIEW 2014 VI block diagram.

    Fig. S6. Effect of print speed on the gel fraction of printed parts.

  • Supplementary Materials

    This PDF file includes:

    • Supplement 1: Derivation of Eq. 1
    • Supplement 2: Derivation of Eq. 2
    • Fig. S1. Wavelength-selective photoinitiation and transient photoinhibition of methacrylate polymerization.
    • Fig. S2. Effect of incident UV and blue illumination intensities on inhibition volume thickness and polymerization rate.
    • Fig. S3. UV-vis spectra of UV and blue light absorbers.
    • Fig. S4. Influence of co-initiator on o-Cl-HABI photoinitiation.
    • Fig. S5. LabVIEW 2014 VI block diagram.
    • Fig. S6. Effect of print speed on the gel fraction of printed parts.

    Download PDF

    Files in this Data Supplement:

Navigate This Article