Tough and Variable-Band-Gap Photonic Hydrogel Displaying Programmable Angle-Dependent Colors
mediaposted on 04.01.2018, 00:00 by Md. Anamul Haque, Kei Mito, Takayuki Kurokawa, Tasuku Nakajima, Takayuki Nonoyama, Muhammad Ilyas, Jian Ping Gong
One-dimensional photonic crystals or multilayer films produce colors that change depending on viewing and light illumination angles because of the periodic refractive index variation in alternating layers that satisfy Bragg’s law. Recently, we have developed multilayered photonic hydrogels of two distinct bulk geometries that possess an alternating structure of a rigid polymeric lamellar bilayer and a ductile polyacrylamide (PAAm) matrix. In this paper, we focus on fabrication of composite gels with variable photonic band gaps by controlling the PAAm layer thickness. We report programmable angle-dependent and angle-independent structural colors produced by composite hydrogels, which is achieved by varying bulk and internal geometries. In the sheet geometry, where the lamellae are aligned parallel to the sheet surface, the photonic gel sheet exhibits strong angle-dependent colors. On the other hand, when lamellae are coaxially aligned in a cylindrical geometry, the gel rod exhibits an angle-independent color, in sharp contrast with the gel sheet. Rocking curves have been constructed to justify the diverse angle-dependent behavior of various geometries. Despite varying the bulk geometry, the tunable photonic gels exhibit strong mechanical performances and toughness. The distinct angle dependence of these tough photonic materials with variable band gaps could benefit light modulation in displays and sensor technologies.
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angle-dependent colorsphotonic gel sheet exhibitstunable photonicPAAm layer thicknessbulk geometrygel sheetrocking curvessensor technologiesVariable-Band-Gap Photonic HydrogelProgrammable Angle-Dependent Colors One-dimensional photonic crystalslight illumination anglesangle dependencesheet geometryangle-independent colorphotonic band gapssheet surfacelight modulationangle-dependent behaviorphotonic hydrogelsductile polyacrylamidephotonic materialsindex variationlamellar bilayergel rod exhibitsband gapsbulk geometries