Advanced Colloids Experiment – Temperature-2 (ACE-T-2)

The Advanced Colloids Experiment-Temperature-2 (ACE-T-2) experiment looks at the assembly of complex structures from micron-scale colloidal particles interacting via tunable attractive interactions. The samples contain suspensions of trifluoroethyl methacrylate (FEMA) colloidal particles (10%vol) of type A and B in binary solvents composed of water (H2O, 68%mass) and lutidine (32%mass), that upon nearing the critical solvent temperature (Tc~32°C) give rise to critical Casimir interactions between the particles. Regulating the temperature enables control of the particle interactions, which for these mixtures of particles A and B are different, leading to the growth of complex structures, and provide a better understanding of how complex interactions lead to complex structures, and to understand the dynamics of growth of these structures.

The experiment has concluded, and science is being evaluated.

The Advanced Colloids Experiment-Temperature-2 (ACE-T-2) investigation studies the self-assembly of precisely engineered colloidal particle mixtures as a function of their interaction strength. Both range and strength of the interactions are controlled via temperature-dependent critical Casimir forces. Particles A and B with different interactions are used to study the formation of complex crystal structures. In these experiments, the research team uses temperature to vary the interaction potential of the particles to study the growth of complex structures from a dilute particle suspension, as a function of the interaction strength. The motion of the individual particles is tracked from microscopic images to follow the growth of the structures both on a single particle and ensemble-averaged level (average structure factor).

These experiments provide insight into complex equilibrium and non-equilibrium structures and the dynamics of their growth.

Previous studies on the aggregation of weakly attractive spherical particles revealed that gravity dramatically affects the final structures formed, and the dynamics of their growth. This conclusion was reached by comparing data taken on ground and on the International Space Station (ISS). Studying the same samples on earth and on the ISS, different structures and different growth mechanisms have been observed. From this comparison, the research team can better understand the physics of nucleation and growth of these structures. This knowledge can be applied to applications in the growth of nanostructures with increasing complexity and increasing colloidal design control.

Understanding self-assembly processes can teach better ways to grow complex nanostructured materials. Furthermore, these experiments provide fundamental insight into the nature of self-assembly, the relation between complex interactions and complex equilibrium and non-equilibrium structures, and the dynamics of both equilibrium and non-equilibrium growth processes.

Space Station Research Explorer