Design and Fabrication of 3D Printed Polymer Composites using Grayscale Stereolithography

Polymer composites are fabricated using stereolithography by spatially modulating the intensity of light used to fabricate a part with regions of varying crosslinking density. A second polymer is preferentially in-swollen into the printed part where crosslinking density is low, thus forming a 3D printed composite with regions of varying stiffness. The initial part is printed using rubbery poly(ethylene glycol) diacrylate which is later swollen with acrylamide. The acrylamide monomer is polymerized to form an interpenetrating network that is glassy in regions where the acrylamide volume fraction is sufficiently high. 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 polymers throughout the composite.