Production of Materials with Spatially-Controlled Crosslink Density via Vat Photopolymerization

We describe an efficient method to produce objects comprising spatially controlled and graded crosslink densities using vat photopolymerization additive manufacturing (AM). Using a commercially available diacrylate-based photoresin, 3D printer, and digital light processing (DLP) projector, we projected grayscale images to print objects in which the varied light intensity was correlated to controlled crosslink densities and associated mechanical properties. Cylinder and bar test specimens were used to establish correlations between light intensities used for printing and crosslink density in the resulting specimens. Mechanical testing of octet truss unit cells in which the properties of the crossbars and vertices were independently modified, revealed unique mechanical responses from the different compositions. From the various test geometries, we measured changes in mechanical properties such as increased strain-to-break in inhomogeneous structures in comparison with homogeneous variants.

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