Fig. 5.

Development of butterfly wing scale photonic nanostructure. (A) TEM cross-section of a ventral wing scale cell from a 9-day-old C. gryneus pupa (from refs. 11 and 21), depicts the complex infolding of the plasma membrane and SER membrane. The developing nanostructure shows the diagnostic motif of two concentric rings roughly in a triangular lattice (compare with Fig.5B). Yellow and red boxes highlight areas revealing different sections through the (110) plane of a polarized (ABCB′A′) pentacontinuous core-shell double gyroid (color insets). (Scale bar: 1 μm.) (Inset) Colored model of a core-shell double gyroid of ABCB′A′ form: A (red) is the extracellular space, B (black) is the plasma membrane, C (white) is the cytoplasmic intracellular space, B' (blue) is the SER membrane, and A' (yellow) is the intra-SER space. [Reprinted with permission from ref. 11.) (B) OsO₄-stained (110) TEM section of an ABC triblock copolymer with core-shell double gyroid morphology. (Scale bar: 200 nm.) (Reprinted with permission from ref. 40. Copyright 2005, John Wiley and Sons.) (C) Three-dimensional model of development of photonic butterfly wing scale cell. (I) Unit-cell volume rendering of the core-shell double gyroid model structure of the form ABCB′A′. Color of each component from inset in A. (II) Single gyroid composed of cell plasma membrane (black) surrounding extracellular space (red). (III) As the scale cell dies, the cellular cytoplasm and membranes (BCB′A′ blocks of the core-shell double gyroid) are replaced with air leaving behind a single gyroid core-shell network of chitin (red) in air.