Mechano-actuated ultrafast full-colour switching in layered photonic hydrogels

Abstract

Photonic crystals with tunability in the visible region are of great interest for controlling light diffraction. Mechanochromic photonic materials are periodically structured soft materials designed with a photonic stop-band that can be tuned by mechanical forces to reflect specific colours. Soft photonic materials with broad colour tunability and fast colour switching are invaluable for application. Here we report a novel mechano-actuated, soft photonic hydrogel that has an ultrafast-response time, full-colour tunable range, high spatial resolution and can be actuated by a very small compressive stress. In addition, the material has excellent mechanical stability and the colour can be reversibly switched at high frequency more than 10,000 times without degradation. This material can be used in optical devices, such as full-colour display and sensors to visualize the time evolution of complicated stress/strain fields, for example, generated during the motion of biological cells.

Bioinspired Nanocomposite Hydrogels with Highly Ordered Structures

“…Afterward, photonic materials with ultrafast responses and a full-color tunable range were also successfully synthesized by using chemically crosslinked hydrogels that were imbedded with reflective PDGI platelets (Figure 8c). [132] The ordered structures that were within the hydrogels not only realized the color-tuning of the light but also reinforced the soft hydrogel network. These hybrid hydrogels Figure 8.…”

“…[127][128][129][130][131][132] The self-assembled polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) polymer formed a simple 1D periodic lamellar structure via amphiphilic interactions, and the P2VP blocks were quaternized and crosslinked to form polyelectrolyte block gel layers (Figure 7c). [127,128] Aqueous solvents modulated the swelling/ deswelling behavior of the polyelectrolyte block gel layers, resulting in changes in both the polyelectrolyte block domain spacing and the refractive-index contrast; accordingly, the wavelengths of light that were reflected by the stop band shifted.…”

“…[109,[127][128][129][130][131][132] By mimicking the structure of colorful tropical fishes, Gong and co-workers fabricated several kinds of hydrogels with well-ordered structures to promote a new generation of sensors. [129][130][131][132] In their work, amphiphilic monomers self-assemble into bilayer structures that can be ordered in one direction (parallel to the substrate surface under shear flow conditions) and then periodically stacked to form lamellar liquid crystals in water. Because of polymerization, the obtained hydrogels contained hard poly(dodecyl glyceryl itaconate) (PDGI) bilayers that exhibited unidirectional alignment in a soft hydrogel network matrix.…”

Block copolymer structural color strain sensor

“…This property gives rise to a useful method for the low-power reflective mode visualization of strain (Table S1, Supporting information) [24][25][26][27][28][29][30][31][32][33][34][35] . In particular, SCs based on self-assembled block copolymers (BCPs) are more suitable, as their periodicities and dielectric constants are readily changed by mechanical forces such as shear, tensile, and compressive forces 24,25,29 .…”

Polymer Adsorbed Bilayer Membranes Form Self-Healing Hydrogels with Tunable Superstructure

“…[24][25][26][27] An interesting example is the dodecyl glyceryl itaconate/acrylamide (DGI/AAm) system. [28][29][30][31] The gel, consisting of poly(dodecyl glyceryl itaconate) (PDGI) that form lamellar bilayers and chemically cross-linked polyacrylamide (PAAm), exhibits many unique functions that are substantially superior to conventional hydrogels, such as structure color, unidirectional swelling, high toughness, and self-healing. Despite these excellent functions, the structure formation mechanism of bilayers and the interaction between the bilayer and the polymer in the hydrogel are still unknown.…”