What’s common between iridescent butterflies/beetles/plants/Opals and multiplexed biosensing: Photonic crystals. Photonic crystals are periodic arrangement of nanostructures-artificial/natural-that affects the way light scatters/diffracts and give the characteristics angle dependent iridescent colors to gems and butterflies
The photonic crystals are attractive for biosensing because crystals of different optical properties can be used as optically encoded particles for multiplexed assays. See my previous report on using encoded particles for biosensing. But because creating large scale periodic structures of nanoparticles is difficult the practical applications of manmade photonic crystals have been limited. However a recent report has combined the super paramagnetic core/shell particles with some cool emulsion based UV curable chemistry to come up with a simple way of fabricating tunable photonic crystals. Prof. Yin and his group at Univ. of California Riverside first made super paramagnetic Fe3O4 nanoparticles that are then covered with a silica shell. The Fe3O4/SiO2 core/shell particles are subsequently encapsulated in UV curable emulsions and then aligned using magnetic field before fixing their orientation by quick UV initiated polymerization of emulsion. The colors of the particles can be tuned by adjusting the distance between core/shell particles. Colors can also be tuned by adjusting the size of the super paramagnetic iron oxide or by adjusting the thickness of SiO2 shell.
Picture Credit Prof. Yin
For multiplexed biosensing, each uniquely color coded particle can be hooked to unique bio-recognition element. The UV curable polymer can be easily functionalized to provide chemical handles to attach proteins and or nucleic acid.
For Biosensing though this approach has tough competition from whole range of alternate particle encoding technologies (see me previous posts on this topic) but hey more options may means better success rate!