Abstract
Self-assembled structures of submicron-sized
colloidal particles are anticipated to serve as innovative optical
materials, including photonic crystals. Colloidal particles with
high refractive indices, which are beneficial for optical
applications, often have a high specific gravity. During the self
assembly process on the ground, they experience gravitational
sedimentation. Consequently, a microgravity environment is
ideal for studying their structural formation. Our group has
participated in colloidal crystallization and cluster formation
experiments aboard the International Space Station. In the
space experiment, we utilized titania particles (TiO2, refractive
index ≃ 2.4, specific gravity ≃ 3) with a diameter of approximately one micrometer. Here, we report the
construction of two-dimensional (2D) colloidal crystals of the titania particles on the Earth, by applying
the knowledge of particle fabrication obtained during the preparation of the space experiment.
Furthermore, we present a preliminary study on stacking the 2D crystal layers of the titania particles. These
results will be valuable for constructing photonic crystals on the Earth and for future space experiments
on colloidal self-assembly.
