Abstract
Tomographic volumetric printing (TVP) physically reverses tomography to offer fast and auxiliary-free 3D printing. Here we show that wavelength-sensitive photoresins can be cured using visible (bar{lambda }=455 nm) and UV (bar{lambda }=365 nm) sources simultaneously in a TVP setup to generate internal mechanical property gradients with high precision. We develop solutions of mixed acrylate and epoxy monomers and utilize the orthogonal chemistry between free radical and cationic polymerization to realize fully 3D stiffness control. The radial resolution of stiffness control is 300 µm or better and an average modulus gradient of 5 MPa/µm is achieved. We further show that the reactive transport of radical inhibitors defines a workpiece’s shape and limits the achievable stiffness contrast to a range from 127 MPa to 201 MPa according to standard tensile tests after post-processing. Our result presents a strategy for controlling the stiffness of material spatially in light-based volumetric additive manufacturing.
Highlights
Tomographic volumetric printing (TVP) physically reverses tomography to offer fast and auxiliary-free 3D printing
If n is the number of voxels needed in one direction to represent a target geometry, the processing time of additive manufacturing (AM) scales with n3-D, in which D is the intrinsic dimensionality of the AM method
When a resin that responds differently to two different wavelengths is used objects with graded stiffness can be produced. This requires the specification of the dose ratio between wavelengths for each voxel individually, which was realized in our setup by installing two light sources that function in parallel in a TVP setting (Supplementary Fig. 1)
Summary
Tomographic volumetric printing (TVP) physically reverses tomography to offer fast and auxiliary-free 3D printing. If n is the number of voxels needed in one direction to represent a target geometry, the processing time of AM scales with n3-D, in which D is the intrinsic dimensionality of the AM method. Computed axial lithography[16] (or tomographic volumetric 3D printing, TVP) was shown to operate on a length scale relevant for tissue engineering[17]. By projecting light patterns from different angles, TVP cures all points in an object in parallel, severing the dependence of printing time on voxel number. It is intrinsically 3D and has a reported resolution of up to ~80 μm[18], with room for improvement. When processing very soft hydrogel or suspended objects, TVP does not require auxiliary support because the geometric integrity of a workpiece is sustained by the viscous, unpolymerized resin
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