Freeze-derived heterogeneous structural color films

Abstract

Structural colors have a demonstrated value in constructing various functional materials. Efforts in this area are devoted to developing stratagem for generating heterogeneous structurally colored materials with new architectures and functions. Here, inspired by icing process in nature and ice-templating technologies, we present freeze-derived heterogeneous structural color hydrogels with multiscale structural and functional features. We find that the space-occupying effect of ice crystals is helpful for tuning the distance of non-close-packed colloidal crystal nanoparticles, resulting in corresponding reflection wavelength shifts in the icing area. Thus, by effectively controlling the growth of ice crystals and photo-polymerizing them, structural color hydrogels with the desired structures and morphologies can be customized. Other than traditional monochromatic structure color hydrogels, the resultant hydrogels can be imparted with heterogeneous structured multi-compartment body and multi-color with designed patterns through varying the freezing area design. Based on these features, we have also explored the potential value of these heterotypic structural color hydrogels for information encryptions and decryptions by creating spatiotemporally controlled icing areas. We believe that these inverse ice-template structural color hydrogels will offer new routes for the construction and modulation of next generation smart materials with desired complex architectures.

Structural Color Ionic Hydrogel Patches for Wound Management

“…First, to investigate the influence of LiCl content on freeze resistance, ionic hydrogels were settled in −20 °C environment for 48 h. It could be found that the ionic hydrogels without LiCl were frozen completely, while the ionic hydrogels with the 2:1 ratio of LiCl/PVA retained their original transparency, indicating excellent antifrozen capability (Figure S8). To further evaluate freeze resistance of SCIHP, a frog-shaped SCIHP was placed on a cooling plate, 36 and the optical and electrical variations were recorded and discussed (Figure S9). It could be found that when the temperature cooled to −20 °C, the structural color of the frogshaped SCIHP remained unchangeable, which was in accordance with reflection peaks results (Figure S10a).…”

Recent Advances in Macroporous Hydrogels for Cell Behavior and Tissue Engineering

“…Ice crystals grow in the polymer solution in a set direction during freezing. When polymers are cross-linked and melted, the removed ice crystals form interconnected anisotropic macro-channels within cryogels [ 119 , 120 , 121 , 122 ]. Anisotropic cryogels supported better cell migration and tissue infiltration than cryogels with randomly distributed pores [ 31 , 123 ].…”

Bioinspired MXene-Based Soft Actuators Exhibiting Angle-Independent Structural Color

“…Furthermore, bioinspired, living, structurally colored soft actuators were reported by assembling engineered cardiomyocyte tissues onto synthetic inverse opal hydrogels, where autonomous shape and color regulation capability was enabled by the cell contraction and elongation in the beating processes of the cardiomyocytes [15]. Compared to chemically colored soft actuators loaded with dyes or pigments [16][17][18][19], physically colored (structurally colored) soft actuators integrated with photonic crystals display brilliant colors that are dynamically tunable by adjusting the lattice constant or refractive index and never fade as long as the periodic structures persist [20][21][22][23][24][25]. However, the structural color of soft actuators reported thus far is dependent on the viewing and light illumination angles, which is one of the critical limitations compared with chemically colored soft actuators.…”