Deformation of Colloidal Crystals for Photonic Band Gap Tuning

Abstract

In this article, we demonstrate the fabrication of colloidal crystals made of polystyrene oblate particles with face centered lattice structures. Monodisperse spherical polystyrene nanospheres were self-assembled into colloidal crystal followed by the infiltration of polydimethylsiloxane (PDMS) precursors into the self-assembled structure. After curing the infiltrated PDMS precursors, the composite colloidal crystals were deformed by compressive stress acting parallel or vertical to the [111] direction of the face centered cubic lattice of the colloidal crystals. After deformation, the shape of the constituent spherical polystyrene particles was changed into oblate ellipsoidal morphology. Depending on the direction of the compressive stress, the stop bands of deformed colloidal crystals were controlled and reflectance spectra were measured to observe the blue-shift or red-shift phenomena of the stop band after deformation. Shear stress was also applied to the composite colloidal crystal to change the morphologies of the constituent polystyrene particles into oblate spheroids, and the stop band position and the band gap width of the reflectance spectrum were modified.

Keywords:

• Colloidal photonic crystal
• oblate ellipsoidal particles
• photonic band gap tuning

Acknowledgments

This research was supported by a grant (code # 2011K000169) from the Center for Nanostructured Materials Technology under the 21st Century Frontier R&D Programs of the Ministry of Education, Science and Technology, Korea.

Y.K.K. is thankful for the support of Basic Research Fund from Korea Institute of Materials Science (PNK2510).