A research team from Georgia Tech's School of Chemistry and Biochemistry has created photonic crystals from hydrogel nanoparticles. By altering the water content of the hydrogels, they found they could tune the optical properties of the photonic crystals.
The self assembling crystal structures can also have various features incorporated into them enabling them to be used as optical waveguides and lenses. The features are added by a photo patterning technique using a frequency-doubled Nd:YAG laser. The laser adds heat to 224nm poly-N-isopropylacrylamide nanoparticles that have additions of gold nanoparticles. The gold converts the laser energy to heat which causes localised melting and subsequent alterations in particle size. The overall crystal structure can therefore be manipulated.