Volumetric 3D printing has emerged as an innovative approach that allows for the creation of complex structures within minutes, with resolutions up to 20 mm. This approach builds the entire object in one step, unlike traditional layer-by-layer techniques, offering greater freedom in design while drastically reducing production time. Recent advances, as demonstrated in our research group, underscore its potential.
Multi-material objects allow overprinting during a second printing operation. A significant challenge for multi-material volumetric 3D printing is the light transparency of the initial structure. Light scattering caused by crystalline microstructures in the first material results in resolution loss during the second printing. The first material must exhibit high transparency (greater than 90%) at 405 nm for successful second printing.
Amorphic polymers show high transparency due to no crystalline microstructures. To leverage this, we created an amorphous 3-armed star (bio)polyester derived from trimethylolpropane, ε-caprolactone, and δ-valerolactone in a 1:1 molar ratio. The star-polyester was end-capped using allyl isocyanate to give -ene endcaps used in thiol-ene photo crosslinking volumetric printing. Through H-NMR, UV-vis, and photorheological measurements, compositions, -ene content (mmol/g), transparency, and crosslinking conditions were determined. High CAD/CAM mimicry was confirmed via CT imaging, optical and scanning electron microscopy.
Developing transparent, mechanically stable, and biodegradable 3D structures tackles a critical hurdle for multi-material volumetric 3D printing.