Floating photonic crystals utilizing magnetically aligned biogenic guanine platelets.

Recently, structural colour formation and light control by accumulated guanine crystals were reported. However, the relationship between light interference by guanine platelets and light intensity in an individual platelet must be examined further. This study presents experimental evidence that the guanine crystal platelets of fishes aid in efficiently controlling the enhancement of light intensity based on light interference between platelets floating in a micro-space. In addition, a magnetic orientation technique enabled us to dynamically modulate the arrangement of platelets floating in water. A group orientation of the platelets under magnetic fields exhibited a distinct enhancement of the light interference between platelets present in the micro-space, and a two-fold enhancement of the reflected light intensity was achieved by comparing two arrangements of magnetically oriented platelets. The developed micro-optic light control method employing tiny platelets floating under aqueous liquid conditions is expected to facilitate the creation of tuneable optical micro-devices, e.g., a micro-'search-light' for individual cell analysis.