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, 10 (1), 791

Multimaterial Actinic Spatial Control 3D and 4D Printing

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Multimaterial Actinic Spatial Control 3D and 4D Printing

J J Schwartz et al. Nat Commun.

Abstract

Production of objects with varied mechanical properties is challenging for current manufacturing methods. Additive manufacturing could make these multimaterial objects possible, but methods able to achieve multimaterial control along all three axes of printing are limited. Here we report a multi-wavelength method of vat photopolymerization that provides chemoselective wavelength-control over material composition utilizing multimaterial actinic spatial control (MASC) during additive manufacturing. The multicomponent photoresins include acrylate- and epoxide-based monomers with corresponding radical and cationic initiators. Under long wavelength (visible) irradiation, preferential curing of acrylate components is observed. Under short wavelength (UV) irradiation, a combination of acrylate and epoxide components are incorporated. This enables production of multimaterial parts containing stiff epoxide networks contrasted against soft hydrogels and organogels. Variation in MASC formulation drastically changes the mechanical properties of printed samples. Samples printed using different MASC formulations have spatially-controlled chemical heterogeneity, mechanical anisotropy, and spatially-controlled swelling that facilitates 4D printing.

Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Representative sets of DLP projections (arbitrary scaling) for UV (top images) and visible light (bottom images), and their corresponding printed specimens. All samples were printed using the BA-1 MASC formulation. Scale bars correspond to 25 mm. a A 3D design resembling a hand with encased internal bones. Picture taken after being removed from toluene. b An EPOX molecular structure signifying the opaque region containing the EPOX-based material. Picture taken on a black background in toluene. c A yin yang design. Picture taken with backlighting in toluene. d An in-house logo for our MASC printing process. Picture taken with backlighting in spearmint oil
Fig. 2
Fig. 2
Representative stress-strain plot and data from tensile testing of HEA-1 samples. a Representative stress–strain plots for uniaxial tensile test HEA-1 specimens each printed with only one light source. To denote each specimen type, we use the light source (UV or Vis) and subscript numbers to indicate the layer cure time in minutes and the thermal post-cure time in hours. For example, UV1,3 samples were produced using UV light with 1-min layer cure times and a 3-h thermal post-cure. b Comparison of relative stiffness of samples at 30% strain; samples printed with UV (purple) or visible light (light gray) from a single vat. c Comparison of ultimate tensile strain of samples printed with UV (purple) or visible light (light gray) from a single vat. d Comparison of Shore A hardness values; samples printed with UV (purple) or visible light (light gray) from a single vat. All error bars correspond to one standard deviation
Fig. 3
Fig. 3
Design, print, and representative stress-strain plot from compression testing of multimaterial HEA-1 printed specimens. a CAD models of 4-pillar multimaterial objects and representative printed specimens. Purple corresponds to pillars printed with UV light and white/transparent outer region corresponds to components printed with visible light. Arrows denote axis of printing: x-axis (blue), y-axis (red), z-axis (green). b Printed specimens: (left) no thermal post-cure; (right) 3-h thermal post-cure at 60 °C; each using 1-min layer cure times. As-printed outer object dimensions: 12 × 12 × 5 mm3. Pillar dimensions: 3 × 3 × 5 mm3 with 2-mm spacing. Scale bar corresponds to 12 mm. c Representative compressive stress-strain plots of HEA-1 specimens. All boxes printed with 1-min layer cure times and post-cured for 3 h at 60 °C. Black (1) = homogeneous sample cured with UV light. Blue (2) = pillar box sample compressed along the z-axis. Yellow (3) = pillar box sample compressed along the x-axis. Red (4) = homogeneous sample cured with visible light
Fig. 4
Fig. 4
Design, print, and representative stress–strain plot from compression testing of multimaterial HEA-2 printed specimen. a CAD model of tetragonal lattice. Purple corresponds to regions printed with UV light and white corresponds to regions printed with visible light. b Printed tetragonal lattice using HEA-2 MASC formulation. Sample printed with 1-min layer cure times, and then thermally post-processed at 100 °C for 10 min. Sample dimensions: 37 × 37 × 13 mm3. Nile Red was used as a dye to reduce visible light-induced outgrowth. c Representative stress-strain plots of compression along all three axes. Black = x-axis with stiff beams printed with UV light. Blue = y-axis with multimaterial beams printed with both UV and visible light. Red = z-axis dominated by soft beams printed with visible light
Fig. 5
Fig. 5
Time-lapse photos of swelling induced actuation in printed sea stars. a CAD models of multimaterial sea star. Tip-to-tip length = 38 mm, core diameter = 9 mm, inlaid beams within each arm = 13 mm. Purple corresponds to UV irradiation and white/transparent corresponds to visible light irradiation. b Swelling results of a sea star in water printed using the HEA-1 MASC formulation. Scale bars = 25 mm. c Swelling results of a sea star in toluene printed using the BA-1 MASC formulation. Scale bars = 25 mm

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