Microscale Photopatterning of Through‐Thickness Modulus in a Monolithic and Functionally Graded 3D‐Printed Part

Abstract

3D printing is transforming traditional processing methods for applications ranging from tissue engineering to optics. To fulfill its maximum potential, 3D printing requires a robust technique for producing structures with precise 3D (x, y, and z) control of mechanical properties. Previous efforts to realize such spatial control of modulus within 3D‐printed parts have largely focused on low‐resolution (from mm to cm scale) multimaterial processes and grayscale approaches that spatially vary the modulus in the x–y plane and energy dose‐based (E = I0 texp) models that do not account for the resin's sublinear response to irradiation intensity. Here, a novel approach for through‐thickness (z) voxelated control of mechanical properties within a single‐material, monolithic part is demonstrated. Control over the local modulus is enabled by a predictive model that incorporates the material's nonreciprocal dose response. The model is validated by application of atomic force microscopy to map the through‐thickness modulus on multilayered 3D parts. Overall, both smooth gradations (30 MPa change over ≈75 μm) and sharp step changes (30 MPa change over ≈5 μm) in the modulus are realized in poly(ethylene glycol) diacrylate‐based 3D constructs, paving the way for advancements in tissue engineering, stimuli–responsive 4D printing, and graded metamaterials.

Keywords

• atomic force microscopy
• digital light processing
• functionally graded materials
• mechanical gradients
• 3D printing