Photonic crystal sensor

Photonic crystal sensors use photonic crystals: nanostructures composed of periodic arrangements of dielectric materials that interact with light depending on their particular structure, reflecting lights of specific wavelengths at specific angles. Any change in the periodicity or refractive index of the structure can give rise to a change in the reflected color, or the color perceived by the observer or a spectrometer.^[1][2] That simple principle makes them useful colorimetric intuitive sensors for different applications including, but not limited to, environmental analysis, temperature sensing, magnetic sensing, biosensing, diagnostics, food quality control, security, and mechanical sensing.^[3] Many animals in nature such as fish or beetles employ responsive photonic crystals for camouflage, signaling or to bait their prey.^[4] The variety of materials utilizable in such structures ranging from inorganic, organic as well as plasmonic metal nanoparticles makes these structures highly customizable and versatile. In the case of inorganic materials, variation of the refractive index is the most commonly exploited effect in sensing, while periodicity change is more commonly exhibited in polymer-based sensors. 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.