Figure 3

Structural analysis of Reflectin films and model for the color change in cephalopods. (a) AFM analysis of surface morphology of colorless Reflectin (R) film. (b) AFM analysis of surface morphology of blue Reflectin/Imidazole (R/I) film. (c) SEM image of surface morphology of colorless R film. (d) SEM image of surface morphology of blue R/I film. (e) SEM image of cross-sectional morphology of colorless R film. Diameters of particles on R film (diameter 1 and diameter 2) were measured along two axes separately (shown as red line and purple line), and the higher magnification of this image is presented inside. Particles exhibit a small globular-like shape (Mean diameter 1: 22 nm, mean diameter 2: 22 nm, n = 588). (f) SEM image of cross-sectional morphology of blue R/I film. Diameters of large platelet-shaped particles on the cross section of R/I film were measured along the long (shown as red line) and short (shown as purple line) axes separately, and the higher magnification of this image is presented inside. Mean diameter 1: 389 nm, mean diameter 2: 299 nm, n = 581. Thicknesses of large platelet shaped particles on the cross section of R/I film were measured (shown as orange line). The thickness ranged from 40 to 108 nm, and the average thickness is approximately 68 nm. (g) Diameters of particles on the cross section of colorless R film and blue R/I film as measured from the SEM image in (e,f). (h) Schematic illustration summarizing the proposed model for the color change mechanism in cephalopods. Structural and mechanistic details elucidated in this manuscript are diagrammed. (See text for details.) The scale bars in (a–f) represent 500 nm, whereas the scale bars in the higher magnification of (e,f) shown in white boxes represent 125 nm.