| 초록 |
Photonic crystals which show structural colors are nano structure in which materials having two different refractive indices are repeatedly arranged. They could be generated by self-assembly of colloidal particles. When attractive force between colloidal particles is dominant, they form single crystalline grains along the inner surface of spherical container. However, it is challenging to produce large-sized grains in microcapsules. Here, we design a centrifugation-assisted crystallization of colloidal particles with depletion-attraction to produce large single crystalline in microcapsules. Double-emulsion droplets containing polystyrene nanoparticles, depletant and salt in the core are microfludically fabricated. After curing of PDMS membrane, polystyrene particles are slowly deposited unidirectionally by centrifugal force. Diffused particles form single crystalline grains by depletion attraction, and they are merged into larger crystallites by Ostwald ripening. Photonic capsules containing large single crystalline show high reflective intensity and have angle dependence. They can be served as micro-compartments of photonic graphics, decoration or anti-counterfeiting. |
