3D printing hydrogel with homogeneous structural color induced by ZnS colloidal spheres for customized multi-channel...

The utilization of structural colors in 3D printing was anticipated due to their eco-friendliness and sustainability. However, the manufacturing of homogeneous structural colors with intricate 3D architectures remains a great challenge, particularly in hydrogels. Herein, we added 0.5 wt% ZnS colloidal spheres supporting Mie scattering into photocurable inks to generate vibrant and homogeneous structural color in the hydrogel, representing 40-100 times decrease of the reported dosage of colloidal spheres in previous work. Through optical simulation, gradient experiments, and evaluation in HSV color space, the ink composition was meticulously optimized for a commercial light-based 3D printer. Our experiments validate the high-throughput manufacturing of structural colored hydrogels with intricate 3D architectures and polychromatic objects, enabling the 1000 prints within 17 min and achieving 200 μm precision. We have also demonstrated the utilization of customizable 3D hydrogels with both structural and luminescent colors, thereby expanding their applications in the multi-channel spatial information encryption.