Advanced Imaging, Folding, and Assembly of Colloidal Molecules (ACE-T-9) - 04.18.18

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Advanced Imaging, Folding, and Assembly of Colloidal Molecules (ACE-T-9) experiment involves the imaging, folding, and assembly of complex colloidal molecules within a fluid medium. This set of experiments not only prepares for future colloidal studies, but also provides insight into the relationship between particle shape, colloidal interaction, and structure. These so-called “colloidal molecules” are vital to the design of new and more stable product mixtures.
Science Results for Everyone
Information Pending

The following content was provided by William V. Meyer, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom:

Principal Investigator(s)
David Marr, Ph.D., Colorado School of Mines, Golden, CO, United States

Co-Investigator(s)/Collaborator(s)
Ning Wu, Ph.D., Colorado School of Mines, Golden, CO, United States
Michael Solomon, Ph.D., University of Michigan, Ann Arbor, MI, United States

Developer(s)
NASA Glenn Research Center, Cleveland, OH, United States
ZIN Technologies Incorporated, Cleveland, OH, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
NASA Research Office - Space Life and Physical Sciences (NASA Research-SLPS)

Research Benefits
Earth Benefits, Scientific Discovery, Space Exploration

ISS Expedition Duration
September 2017 - August 2018

Expeditions Assigned
53/54,55/56

Previous Missions
Information Pending

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Experiment Description

Research Overview

  • Nature assembles relatively simple atomic and molecular building blocks into well-defined structures of exquisite complexity and functionality. Scientists and engineers desire a similar capability to produce advanced functional materials efficiently, however, the difficulty in characterizing molecular processes in situ greatly limits our current understanding. Although decades of study using colloids as molecular mimics have shed significant light, the range of particles employed to date has been limited to relatively simple symmetries. The full diversity of fundamentally and technologically-relevant phases remains to be accessed due to a limited control of intrinsic colloidal interactions and a reliance on non-directed assembly. Pushing beyond these limitations helps to develop colloidal building blocks that better model natural molecules with varying composition, complex architecture, and external field-responsive interactions.
  • In the Advanced Imaging, Folding, and Assembly of Colloidal Molecules (ACE-T-9), the imaging capability, folding dynamics, and assembly behavior of linear colloidal chains, colloidal dimers, and lock-and-key particles are studied by the combination of a proper design of particle architecture and tunable colloidal interactions (e.g., double layer repulsion and hydrophobic attraction). In the case of colloidal chains, for example, the single chain dynamics should sensitively depend on the chain flexibility and monomer-solvent interactions. The goal is to observe qualitative (pre-confocal) three-dimensional, real time dynamics of single colloidal chains under the microgravity environment. Also the experiment aims to observe three-dimensional structures assembled from colloidal dimers and lock-and-key particles and to measure the binding equilibrium constants that are impossible to measure in earth experiments due to the effect of sedimentation.
  • In-situ manipulation of anisotropic interactions and dynamic pathways, based on rational colloidal particle design and proper use of external fields, could lead to crystalline and aperiodic structures beyond those seen in nature. With the wide variety of attributes that characterize anisotropic interactions, previously inaccessible regions of complex phase space are probed. These studies move significantly beyond hard spheres and towards experimental models appropriate for studying fundamental questions associated with complex symmetries. Results can lead to improved control of non-covalent assembly of molecules, efficient tailoring of lattice symmetries, and the scalable processing of nano-structured materials. The development of new colloidal molecules and their associated assembled structures have considerable technological impact as well. Such structures generally lead to arrays with reduced symmetry and enhanced directionality. They can interact with a broad range of electromagnetic radiation in unique ways and can exhibit collective photonic, plasmonic, mechanical, electronic, or magnetic properties that are not manifested at the level of single particles. As a result, they have significant potential as next-generation functional materials.

Description

Although decades of study using colloids as molecular mimics have shed significant light, the range of particles employed to date has been limited to relatively simple symmetries. The full diversity of fundamentally and technologically-relevant phases is yet to be accessed. The key difference between conventional colloidal models and real molecules is the former usually lacks directional interactions. Pushing beyond this limitation helps to develop colloidal building blocks that better model natural molecules with varying composition, complex architecture, and external field-responsive interactions. The fabrication and subsequent assembly of these "molecules" allow the study of outstanding questions with more realistic models with profound technological impact.
 
The Advanced Imaging, Folding, and Assembly of Colloidal Molecules (ACE-T-9) research tests the microscopy imaging capability on the colloidal molecules (colloidal chains, dimers, and lock-and-key particles) created in space. This lays the foundation for subsequent investigation of them under electric fields when the electric cell module becomes available in near future. The colloidal chains are fabricated by combining both magnetic fields and Michael-addition reaction. An external magnetic field is used to align functionalized superparamagnetic spheres into linear chains of different lengths, and the Michael-addition reaction chemically links neighboring monomers in the same chain. The mechanical properties of those chains change as a function of reaction temperature, time, and linker length. The Light Microscopy Module (LMM) images the dynamics of single colloidal chains in bright field to capture the real-time, (quantitative [without confocal]) three-dimensional movement of monomers on single chains. The impacts of chain flexibility on dynamics are studied by both designing different chains, and varying salt concentrations.
 
The second objective of this research is to study the self-assembly of colloidal dimers and lock-and-key particles. Colloidal dimers have two lobes fused together, but one lobe has distinct interfacial, compositional, or physical properties from the other. Lock particles are colloidal spheres with well deļ¬ned cavities synthesized from monodisperse emulsions. Key particles are spheres that possess the right curvature to match the size of the lock particles. Lock and Key particles can assemble, at the right experimental conditions, due to the depletion-driven lock-and-key interactions. During the past few years, dimer particles with combined geometric and interfacial anisotropies, such as the metallodielectric dimers and dimers with quadrupoles have been successfully fabricated. It has been found that colloidal structures assembled from dimers sensitively depend on the relative orientation between neighboring dimers. In this research, the relative strength of double layer repulsion and hydrophobic attraction on both dimers and lock-and-key particles are tuned, by adjusting the salt concentration in solution. The three-dimensional self-assembled structures and the binding equilibrium constants under microgravity environment are imaged/measured using both bright field and fluorescence microscopy.

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Applications

Space Applications
Large colloidal molecules, such as linear chains with tens to hundreds of monomers, settle quickly on earth. This work expands the capability and lays the foundation to assemble complex colloids into three-dimensional structures, under the microgravity environment.

Earth Applications
This work tests the imaging capability for large and complex colloidal molecules. It also probes the combined impacts of particle shape and colloidal interactions on assembly. This understanding can lead to improved control of non-covalent assembly of molecules, efficient tailoring of lattice symmetries, and scalable processing of nano-structured materials.

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Operations

Operational Requirements and Protocols

The microscopy imaging capability of colloidal molecules in a fluidic environment is tested in the microgravity environment. The imaging goal is to observe (1) real-time and three-dimensional particle centroid positions of colloidal chains and colloidal molecules over both short (30 minutes) and long periods (one week); (2) assembled structures and to resolve particle centroid positions for colloidal dimers and lock-and-key particles. For short-time imaging, the video should be taken with 5 fps over 30 minutes. For both cases, the x-y positions of particles should be determined with less than 5% error (with respect to particle diameter). The z-positions should be determined within 1 micron. For fluorescence imaging, lamp should be shuttered between image sets to prevent sample bleaching.
 
Once successful, further study is carried out of the folding dynamics of single colloidal chains where the chain architecture can be varied systematically and the monomer-solvent interaction can be tuned by varying salt concentrations. Furthermore, by tuning the balance between electric double layer repulsion and hydrophobic attraction on both colloidal dimers and lock-and-key particles, the assembly of those colloidal molecules into complex three-dimensional structures and the binding equilibrium constants can be studied and measured.

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Decadal Survey Recommendations

CategoryReference
Applied Physical Science in Space AP5
Fundamental Physical Sciences in Space FP1

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Results/More Information

Information Pending

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Related Websites
2011 ACE SCR
ISS Light Microscopy Module

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Imagery