Structure formation of charged colloids under microgravity and its applications

Abstract

  Charged colloidal particles form a variety of association structures in their dispersions due to electrostatic interactions acting between them. The microgravity environment, where the sedimentation effect is negligible, is ideal for studying the structure formation of colloidal particles with high specific gravity. In this paper, we report a recent space experiment on the association (clustering) of charged colloidal particles under microgravity conditions in the International Space Station (JAXA Colloidal Clusters Formation Project). The average association number and the regularity of the clusters under microgravity were larger than those on the ground. Based on the findings obtained through the space experiments and ground-based investigations during the preparation of the experiment, we were also able to fabricate a two-dimensional diamond lattice structure in which tetrahedral colloidal aggregates are regularly arranged in a series on a two-dimensional substrate.