• Weiner, Steve
• Gur, Dvir
• Elad, Nadav
• Addadi, Lia
• Palmer, Benjamin A.
• Hirsch, Anna
• Kronik, Leeor
• Leiserowitz, Leslie

Abstract

<p>Guanine crystals are widely used in nature as components of multilayer reflectors. Guanine-based reflective systems found in the copepod cuticle and in the mirror of the scallop eye are unique in that the multilayered reflectors are tiled to form a contiguous packed array. In the copepod cuticle, hexagonal crystals are closely packed to produce brilliant colors. In the scallop eye, square crystals are tiled to obtain an image-forming reflecting mirror. The tiles are about 1 mm in size and 70 nm thick. According to analysis of their electron diffraction patterns, the hexagon and square tiles are not single crystals. Rather, each tile type is a composite of what appears to be three crystalline domains differently oriented and stacked onto one another, achieved through a twice-repeated twinning about their &lt;011 &gt; and &lt;021 &gt; crystal axes, respectively. By these means, the monoclinic guanine crystal mimics higher symmetry hexagonal and tetragonal structures to achieve unique morphologies.</p>

Topics

• impedance spectroscopy
• morphology
• single crystal
• electron diffraction
• composite
• forming