Mechanism Of Structural Color In Creatures And Bionic Design Of Structural Color

Structural color is caused by the interaction of light with minute structures which geometries are on the order of magnitude of visible light wavelengths. It can be found in many creature bodies. Unlike chemical pigment, this type of color has many good properties, such as no fade, no pollution, iridescent. The structural color has widely potential applications in many fields such as display, decoration, anti-counterfeiting techniques. Studying the mechanism of structural color in creatures can not only lead us to understand the color principle but also help us to use this principle for many applications.1. The structural color has attracted widely attention because of the complicated relationship between the color and microstructure. The description of microstructure and establish of optical model is a continuous developing and improving process. In order to understand mechanism of butterflies, we use SEM and TEM to characterize the dimension of the scale on the butterfly wing and set up corresponding structural models. Using FDTD method, the optical properties of models are calculated and corresponding color are obtained. The colors of structural models affected by some parameters are also studied. The shinning blue on the wing of S.C. formosana mainly comes from the parallel ridges on scales. The titled angle between the scale base and laminas of ridge will affect the structural color. When the angle is not less than 10 degree, the structural color can be calculated from the two-dimensional tower model. When the angel is increased, the dominated wavelength of color will shift to the longer wavelength and brightness of color will increase. The wings of the two Papilio butterflies, P. P. Fabricius and P. lorquinianus, have two kinds of scales, cover scale and ground scale. And their structural colors mainly come from the cover scales. The ridges on the cover scales have little effects on structural color. And shape of concavity on cover scale surface will affect the structural color. When the depth of concavity is increased, the dominated wavelength of color will shift to short wavelength and brightness will become dim.2. The colloidal crystal with opal structure has great potential applications in many fields. It can exhibit distinct structural colors that resulted from incomplete photonic band gap and tunable color can be obtained by changing the refractive index contrast and lattice distance. Two kinds of colloidal crystals are fabricated and used to realize tunable color by changing lattice distance and refractive index contrast between the particles and the medium among the particles. Through experiment and simulation analysis, the stop band characteristic of colloidal crystal is affected by the refractive index contrast and the lattice distance. The shift of peak position is nearly linear to the lattice distance even if the refractive index contrast is different. Longer tunable color range and narrower bandwidth can be obtained in the colloidal crystal with lower refractive index contrast. Colloidal crystal with lower refractive index contrast has lower reflective intensity. The peak intensity is also related to lattice distance and there is an optimal lattice distance where colloidal crystal can get highest peak intensity. Such an investigation can help us to acquire nice tunable color by changing the stop band characteristic on the colloidal crystal.3. The structural color is mainly come from the microstructure rather than pigment. Through studying the mechanism of structural color in some creatures, we try to design microstructure in texitle fibres which can produce structural color. The superfine sea-island textile fibre which cross-section shape is like faviform has high quality color and its color is not sensitive to the incident light angle.