In order to make the three-dimension crystal structure by polystyrene beads, we dried colloidal suspension of polystyrene beads on a glass plate. Then we completely covered the sample with Silicone liquid and dried it on a hot plate of 60°C slowly to dry colloidal suspension of polystyrene beads uniformly. After having crystallized, we wiped off silicon solution on the surface of the sample with Kim-wipes and infiltrated it with premixed elastomer of PDMS. We dried it at room temperature overnight, then at 55°C for six hours and expressed the structural color on the glass plate.
We observed these polystyrene beads with SEM. The device which we used is field emission type scanning microscope FE-SEM Hitachi, Ltd.S-4700. We coated the surface of polystyrene beads with platinum/palladium layer of approximately 10nm in thickness as the preprocessing before observation. After having frozen it in liquid nitrogen, we prepared two kinds of sample. One is a sample that the glass plate was broken. The other is a sample that the top layer was merely torn off. We observed these at acceleration voltage 3.0kV.
Hiroshi Fudouzi and Younan Xia,;Langmuir 2003, 19, 9653-9660