Advanced Colloids Experiment-Temperature control-1 (ACE-T-1) - 04.25.18

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

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Science Objectives for Everyone
Advanced Colloids Experiment-Temperature control-1 (ACE-T-1) studies tiny suspended particles which have been designed by scientists to connect themselves in a specific way to form organized structures within water. Materials having complex structures and unique properties potentially can be made with more knowledge of how these particles are joined together and the conditions which control their behaviors. The particular type of particles used in ACE-T-1 are referred to as Janus particles, named after the two faced Roman god Janus because these particles may be said to have "two faces" since they possess two distinct types of properties. The Janus particles being studied have one half of their surface composed of hydrophilic groups (which interact with water) and the other half of hydrophobic groups (which are repelled from water). The microgravity environment on the International Space Station (ISS) provides researchers insight into the fundamental physics of micro particle self-assembly and the kinds of colloidal structures that are possible to fabricate. This in turn helps manufacturers on Earth in choosing which high-value material is worth investigating.
Science Results for Everyone
Information Pending

The following content was provided by Chang-Soo Lee, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: ACE

Principal Investigator(s)
Chang-Soo Lee, Ph.D., Chungnam National University, Daejeon, South Korea

Co-Investigator(s)/Collaborator(s)
Information Pending

Developer(s)
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
Scientific Discovery, Earth Benefits

ISS Expedition Duration
March 2016 - February 2018

Expeditions Assigned
47/48,49/50,51/52,53/54

Previous Missions
Information Pending

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Experiment Description

Research Overview

Important advances are now being reported in the literature regarding the effects of shape controlled colloidal building blocks: these include spheres, dumbbells, and patched building blocks. However, these 2-D advances still need to be extended to 3-D to make complex building blocks (with 3-D shape anisotropy, constructed using the convex and flat ends of Janus particles) and this requires microgravity.
 
Scientists at Chungnam National University have established a general way to synthesize shape anisotropic building blocks (on the submicron to micron scale) that enables us to make the transition from 2-D to 3-D morphology. These anisotropic building blocks have the potential to be assembled into highly complex structures. However, on Earth, self-assembly is spatially hindered by gravitational sedimentation; while, on the ISS, the detrimental effects of gravity are eliminated. The Advanced Colloids Experiment-Temperature control-1 (ACE-T-1) experiment in microgravity enables the 3-D spatial organization of the building blocks that can be controlled by shape anisotropy (as indicated in Figures 1 and 2).
 
The fundamental understanding of self-assembly with anisotropic building blocks gained from this work is crucial for providing the foundation needed for the design and fabrication of novel materials with highly ordered and complex architectures.

Description

Self-assembly has been explored as a novel strategy for making new functional materials with unique physical, chemical, and mechanical properties in various fields. To date, many assembly building blocks and techniques have been introduced from molecular to meso-scale, which rely on chemical and physical driving forces.
 
Janus particles are named after the two-faced Roman god Janus because these particles may be said to have "two faces" since they possess two distinct types of properties. These particles are considered as a favorable building block to make various structures. On Earth, their configurations are confined by gravity to form 2-D structures (when the particle concentration is not so high that they stack). However, to achieve complex 3-D structure in self-assembly requires further complexity in particle shapes. Several techniques were reported in literature providing variety in shapes but, it is still difficult to make 3-D shapes such convex or concave particles. In space, microgravity allows Janus particles to form unique 3-D structures.
 
The Janus particles being studied have one half of their surface composing of hydrophilic groups and the other half of hydrophobic groups. Advanced Colloids Experiment-Temperature control-1 (ACE-T-1) lays the foundation for future ISS work with smaller particles to study the kinetics driving self-assembly (in the absence of sedimentation).

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Applications

Space Applications
Observing colloidal interactions without the influence of gravity provides new insight into how unhindered particles form network and structures. Results from ACE-T-1 lays a foundation for understanding this mechanism. Very small scale self-assembly of materials can be an efficient method to build new materials and equipment in space.

Earth Applications
The ACE-T-1 investigation seeks to answer fundamental questions about behaviors of colloids, helping scientists to understand how to control, change, and even reverse interactions between tiny particles. This knowledge is crucial for developing self-assembling, self-moving, and self-replicating technologies for use on Earth. It is anticipated that this novel fabrication approach can be applied to produce novel functional material in various applications such as self-assembly, photonics, diagnostics, and drug-delivery.

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Operations

Operational Requirements and Protocols
The experiment consists of two modules. Run one experiment module (each module contains 3 or more capillary cells) per week. Microscopic observation is expected to require 1–4 days. Inspect each capillary for air bubbles using a low magnification objective and analyze data, re-write scripts, adjust parameters, etc. Switch capillary if air bubbles exceed allowable size. ACE-T-1 ground team uses balance of experiment time, i.e., the rest of the week, to analyze data, re-write scripts, adjust parameters.
Experiment Steps: Crew member inspects samples (to determine whether or not large bubbles exist in the sample capillary cells). The first sample to be run is selected based on the above bubble size observations; from this, feedback will be provided to the crew on which sample well strips to install in the microscope. Crew member mixes sample wells using motorized magnetic stir bar in the condenser until that particles are randomized; ground testing is used in advance of the flight to ensure that 2 minutes per capillary cell is appropriate. Microscope XYZ offsets are defined (assembly alignment per ACE-T-1 method) and camera parameters are adjusted using 25x objective. Crew member surveys capillary cell(s) at 25x to determine primary test locations (select locations away from stir bar or bubble) and secondary region of interest, then moves sample to first regions of interest (ROI). Using 40x air objective, crew member focuses on the bottom surface of the particle assembled structure. The crew operator records camera parameters using the 40x air objective and records best z-depth at each primary test location (record at five z-depths (e.g. 2, 4, 6, 8, and 10 microns) each ROI. Ground research team would like to use 40x air objective at intervals of 3 hours for 4-5 days. Addition experimentation with the GIU will inform if microscope needs to switch to 63x air objective to see the bond structures. The imaging goal is to characterize and analyze the assembled formation/structures.

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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
ACE website
The 2011 ACE Science Concept Review (SCR)
LMM microscope on the ISS

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Imagery

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The self-assembly of particles with anisotropic shapes on Earth versus microgravity (2-D vs. 3-D assembly).  Image courtesy of Professor Chang-Soo Lee – CNU.

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Cylindrical Janus particles with flat hydrophobic and hydophillic ends self-assemble in 3-D in microgravity. 1-g shown on left. Anticipated micro-g shown on right. (Image courtesy of Professor Chang-Soo Lee – CNU.

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Cylindrical Janus particles with convex hydrophobic and flat hydophillic ends self-assemble in 3D in microgravity. 1-g shown on left. Anticipated micro-g shown on right.  Image courtesy of Professor Chang-Soo Lee - CNU.

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image Nasa Image: ISS026E032514 - European Space Agency astronaut Paolo Nespoli operating the Light Microscopy Module microscope aboard the International Space Station.
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image NASA Image: JSC2004E41590 - The Light Microscopy Module (LMM) features a modified Leica RXA research imaging light microscope with powerful laser-diagnostic hardware and interfaces.
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