Advanced Colloids Experiment-Temperature 4

Original Objective: The ACE-T4 experiments were designed to explore the disorder-induced transformation between a crystal and a glass. The experiments introduced disorder by added colloidal dopants into the samples; these dopants introduce structural frustration into the crystals which, in turn, can transform the crystals into disordered solids (polycrystalline) and glasses with novel mechanical properties. The experiments varied the concentration and character of particle dopants in three-dimensional colloidal crystals and employed direct visualization of an evolving crystal microstructure and dynamics in microgravity to derive fundamental insight into the nature of the transition and the glasses formed.

Revised Objective: Before the ACE-T4 experiment on the International Space Station (ISS) was conducted, the master hard disk controlling the Light Microscopy Module (LMM) failed and delayed starting this experiment by many months. This extended delay had a detrimental effect on the samples that resulted in the gelation of the samples before the experiment began. The originally planned experiments were no longer possible due to gelation, but the ACE-T4 experiment based on the changed samples (gels) provided qualitatively different insights into the behavior of 3D colloidal gels over a range of temperatures and temperature gradients. Some effects were visible with LMM and provide an opportunity to study the microstructure, dynamics, and stresses in gels that can lead to microcracks, an important problem that, for example, could affect 3D printer inks.