Unidirectional Alignment of Lamellar Bilayer in Hydrogel: One‐Dimensional Swelling, Anisotropic Modulus, and Stress/Strain Tunable Structural Color

Abstract

A novel anisotropic hydrogel, consisting of lamellar bilayers and a polymer network, with unidirectional alignment of the bilayer structure has been synthesized. The unidirectional orientation of bilayer in the gels leads to one‐dimensional swelling, strong anisotropy in elastic modulus, and exhibits excellent visible color. The gel shows reversibly tunable structural color under mechanical stimulation and could be the basis for a deformation‐based color display.

Multi-functions of hydrogel with bilayer-based lamellar structure

“…Therefore, an anisotropic hydrogel film (thickness: 500 m, length: 10 cm, width: 1 cm) was obtained in which lamellar bilayer sheets oriented parallel to the wide surface of the film. At the as-prepared state, the sheet-shaped anisotropic PDGI/PAAm gel films are almost transparent and show Bragg's diffraction in ultra-violet wavelength band (λ max~ 200400 nm; d~ 85170 nm), but after reaching equilibrium swelling in water, they exhibit excellent visible color (λ max ~ 400700 nm) with an inter bilayer spacing, d~ 170300 nm [28].…”

“…Haque et al succeeded to fabricate the structure uniformity of the hybrid gel by aligning the bilayer sheets in one direction before polymerization, i.e, macroscopic uni-domain lamellar bilayer structure fixed inside the polymer matrix of the PAAm hydrogel after polymerization [28] which is summarized in solution was injected, with a pipette, into the 500-m-thick reaction cell of 10 cm length and 1 cm width. The injection speed of the solution was about 5 cms -1 , corresponding to a shear rate of 200 s -1 .…”

“…However, this micro-domain lamellar superstructure in hydrogel plays negligible improvement in the functional hybrid gel material due to the poly-domains of the lamellar phase in macro-scale [24][25][26][27]. Very recently, Gong's group has developed a successful method for formation of macroscopic (integrated microscopic) single-domain lamellar bilayer structure with periodical stacking inside the polymer matrix of the hydrogel [28,29]. The hybrid hydrogel system 4 already attracted great attention in material science because two novel phenomena, excellent mechanical performances and tunable structural color, are emerged in one material.…”

Biocompatible and Sustainable Optical Strain Sensors for Large‐Area Applications

“…By simply sandwiching the HPC water mesophase with polymer sheets, we obtain robust, large area and flexible strain sensors able to detect different types of deformation (e.g., compression, shear, and exten sion) from the optical signature. The fabricated sensors, there fore, overcome the shortfalls of conventional photonic crystal strain sensors, such as a lack of scalability [23,24] and incompat ibility with dry environments [25,26] and conventional electrical …”

Tunable structural color in organisms and photonic materials for design of bioinspired materials

“…Lu et al reversibly changed the color of a swollen lamellar block-copolymer film from violet to red by applying a voltage of 2.5 V [48]. Haque et al used a different approach, namely, unidirectional alignment of a lamellar bilayer in a polyacrylamide hydrogel [49]. The membrane like lamellar bilayer structure changed the color of the hydrogel between red and blue upon swelling or application of stress/strain.…”