One-Pot Strategy to Prepare Structurally Colored Alginate Dispersions for Functional Applications

Structural colored hydrogels have emerged as a class of flexible optical materials with broad application prospects in smart color displays, wearable devices, sensors, and beyond. However, conventional preparation methods are often limited by time-consuming procedures and limited production scales. In this work, a structural colored sodium alginate (SA) dispersion was prepared by simply mixing an SA solution with an ultralow concentration of poly(styrene-methyl methacrylate-acrylic acid) colloidal emulsion and a small amount of cuttlefish ink. Depletion-induced interactions between the polymers drive the assembly of colloids into short-range ordered arrays within confined domains. When dominant scattering is suppressed, weak reflection signals become visible. Leveraging the ion-cross-linking capability of SA, the structural colored dispersion can be solidified via rapid gelation with CaCl₂ or through a mild treatment using slow-releasing Ca²⁺ sources. As a result, the structural colored SA dispersion can serve as a functional ink for fabricating fibers and hydrogels through various solution-based processing techniques such as wet spinning, coaxial printing, dip coating, and extrusion-based 3D printing. This study demonstrates that the one-pot preparation of structural colored polymer dispersions offers a versatile and promising platform for diverse applications.