Electrochromic effect refers to the electrically tunable coloration of a matter. Emerging see-through color-tunable applications pose a synergetic demand on electrochromic device, concurrently having ultralow field driving, operation in transmissive mode, and high-purity and tunable interference colors of sci-fi perception. However, such an electrochromic device remains elusive. Herein, we invent a transmissive electro-interference-color device based on two-dimensional titania liquid crystals (2D TiO2 LCs), demonstrating a record-high electroresponse sensitivity of ~1.5 × 10−7 square meters per square volt among all wide-bandgap media. Consequently, the device works under an electric field of 6 × 103 volts per meter (three orders of magnitude lower than that of conventional LCs), operates in a transmissive mode with ~85% transparency, and displays pure and tunable interference colors. The electro-interference-color device serves as a good example to fabricate diverse see-through chromatic applications as conceptually demonstrated smart windows with functions of privacy protection, energy saving, and artistic presentation as well as transparent display.
The birefringent response of elastomer materials with rich polarized interference colors is promising in the field of stretchable optical areas. Increasing the accessible change number of interference colors during stretching birefringent materials is important for optical strain display. Here, we can fabricate birefringent elastomers with multicolor response of polarized interference color via compositing with highly oriented cellulose nanocrystals (CNCs), transparent one-dimensional biomass nanocrystals with excellent birefringent properties, which exhibit sensitive, reversible, and controllable changes of interference color during stretching in perpendicular to the orientation of the CNCs. Employing a layer-by-layer shearing process of CNC aqueous dispersion, solvent exchange of monomers, and in-situ polymerization, we can produce birefringent elastomers with high optical path difference (>1500 nm) due to the high birefringence (2.81 × 10 −3 ) and high thickness (within 1 mm). In addition, the high retardation of the birefringent elastomers is conducive to more interference color changes when stretching perpendicularly to the direction of oriented CNCs. Then, we demonstrate this birefringent material capable of fabricating a polarized-optical strain display by utilizing the multicolored responses during the stretching process.
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