Fig. 4

Hydrogels used for printing, fiber formation, and coatings. a−d Demonstration of hydrogel printing by submerging a pre-printed polymer/THF solution into water. a Colorless SOS(69-156-69)/THF solution before water submersion. b Development of structural color after immersing the printed SOS(69-156-69)/THF solution into water. c, d Printed hydrogels of SOS(8-65-8) hydrogel loaded with c gold nanoparticles (10 wt% gold with respect to the polymer) and d the hydrophobic dye indigo. e UV−Vis spectrum of AuNPs in THF, SOS(8-65-8) microgel loaded with AuNPs, SOS(8-65-8) hydrogel, and SOS(8-65-8) hydrogel loaded with AuNPs. The AuNPs-loaded hydrogel was prepared from rapid-injection of a THF solution of 10 wt% SOS(8-65-8) with AuNPs (10.0 wt% with respect to polymer). f Structural colored hydrogel fibers created by injecting a SOS(69-156-69)/THF solution into water. g Complex hydrogel mesh created by submerging a preprinted mesh using different polymer inks (SOS(69-156-69)/THF and SOS(8-65-8)/gold nanoparticle/THF solution) into water. In the mesh, structural colored hydrogel fibers are horizontally arranged (blue arrow) and plasmonic hydrogel fibers (red arrow) are vertically arranged. h, i Hydrogel coatings on a faceted glass sphere. The glass sphere is able to be coated with h a plasmonic hydrogel layer, or i a structural colored hydrogel layer. The coatings were fabricated by submerging a cleaned faceted glass sphere into h a THF solution of 10 wt% SOS(8-65-8) with AuNPs (10 wt% with respect to polymer), and i a THF solution 10 wt% SOS(69-156-69). Source data are provided as a Source Data file. THF tetrahydrofuran