Lithographic Crystallinity Regulation in Additive Fabrication of Thermoplastics (CRAFT)

For semicrystalline polyolefin thermoplastics, the balance between
interconnected ordered crystalline and disordered amorphous regions is
paramount to their performance and processability. However, contemporary
manufacturing strategies, from injection molding to 3D printing, result in
monolithic objects, unable to spatially encode crystallinity. We present
the discovery of a light-based approach for fabricating mechanically
robust polyolefin thermoplastics with microscopic control over
crystallinity in 3D space. We unveil that light dosage governs polymer
stereochemistry, giving access to a continuum of materials, from strong,
rigid plastics, like HDPE, to more extensible materials akin to LDPE, all
at the flick of a switch. Applying this finding to lithographic grayscale
3D-printing in a process we term CRAFT for Crystallinity Regulation in
Additive Fabrication of Thermoplastics results in rapid multimaterial
fabrication of high-fidelity objects.