ABSTRACT
In the early 1970s, Michael F. Land concluded in a review paper that multilayer interference plays an important role for structural colors in animals [Land 1972]. The multilayer consists of nanoplates of guanine or chitin that are high refractive index materials. Furthermore, it is known that the skin of some fish and insects can change their structural color [Berthier 2007, Oshima 2005]. There are different mechanisms of tuning structural color
CONTENTS
5.1 Tunable Structural Color in Colloidal Photonic Crystal ...................... 141 5.1.1 1D Photonic Crystal Materials with Tunable Structure
Color ............................................................................................. 144 5.1.2 Structural Color of 3D Colloidal Crystals .................................. 144 5.1.3 3D Photonic Crystal Materials with Tunable Structure
Color ..............................................................................................146 5.1.4 3D Photonic Crystal Materials with Tunable Structure
Color by Swelling ........................................................................... 147 5.1.5 Colloidal Crystal Gels with Tunable Structural Color
by Applying Mechanical Stress ................................................... 149 5.1.6 Summary and Outlook ................................................................. 152
References ............................................................................................................. 152 5.2 Moth-Eye Antireflection Surface Using Anodic Porous Alumina ..... 155
5.2.1 Review of Films for Diminishing Reflection ............................. 156 5.2.2 Production Process of the Moth-Eye Antireflection Film ........ 157 5.2.3 Characteristics of the Moth-Eye Antireflection Film ................ 160 5.2.4 Summary ......................................................................................... 162
References ............................................................................................................. 163
in nature. Three key factors, refractive index, periodic nanostructure, and incident light angle, affect the change of structural color. Figure 5.1(a) shows a tropical damselfish (Cobalt Blue, Pomacentridae). This fish can reversibly change its skin color from cobalt blue to green in response to changing surrounding conditions. Kasukawa et al. [1987] studied the mechanism of color change in damselfish and proposed the mechanism shown in Figure 5.1(b). In the iridophore, nanosized single-crystalline reflector plates of guanine are arrayed regularly and show tuned interspacing. The refractive index of the reflector is 1.83, and the one of the surrounding cytoplasm is 1.37 [Oshima 2005]. The structural color change is induced by the motility of the reflector plates. The skin color of the damselfish reversibly changed from blue at d1 to green at d2.
