[citation needed] Many animals in nature such as fish or beetles employ responsive photonic crystals for camouflage, signaling or to bait their prey.
Besides their small size, current developments in manufacturing technologies have made them easy and cheap to fabricate on a larger scale, making them mass-producible and practical.
[7] As chemical analytes have their own specific refractive indices, they can fill porous photonic structures, altering their effective index and consequently their color in a finger-print like manner.
Commonly, they are based on the deformation-induced change in the lattice constants in flexible materials such as elastomeric composites or colloidal crystals, causing a mechano-chromic effect as they stretch or contract.
Compared to traditional optical fibers, they are highly birefringent with tailorable dispersion, limited loss and endless single-mode propagation for a long range of wavelengths and have a very fast sensing response.