Selectable Optical Diagnostics Instrument - Aggregation of Colloidal Solutions (SODI-Colloid) - 05.17.18

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ISS Science for Everyone

Science Objectives for Everyone
Selectable Optical Diagnostics Instrument - Aggregation of Colloidal Suspensions (SODI-Colloid) will study the aggregation, or mass, phenomena of colloids in the microgravity environment onboard the International Space Station.
Science Results for Everyone
In this microgravity-based investigation of colloids (mixtures of evenly distributed particles), researchers were able to change the strength of particle interactions by using a binary mixture solvent and increasing the temperature. Fractal structures formed through diffusion-limited aggregation even at the lowest strength of attraction, while complexity of patterns decreased with increasing attraction. Ground experiments produced only one type of aggregate with a constant pattern, formed by a reaction-limited process. These results demonstrate that it is possible to fine-tune colloid interaction forces by changing the temperature and to investigate aggregation mechanisms and the resulting structure of colloidal solids.

The following content was provided by Gerard Wegdam, Ph.D., and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Erasmus Experiment Archive.
Experiment Details


Principal Investigator(s)
Gerard Wegdam, Ph.D., University of Amsterdam, Institute of Physics, Amsterdam, Netherlands

Theyencheri Narayanan, Ph.D., European Synchroton Radiation Facility, Grenoble, France
Marco A. C. Potenza, Ph.D., University of Milan, Milan, Italy
Peter Schall, Ph.D., University of Amsterdam, Institute of Physics, Amsterdam, Netherlands

Verhaert Design and Development, Antwerp, Belgium

Sponsoring Space Agency
European Space Agency (ESA)

Sponsoring Organization
Information Pending

Research Benefits
Information Pending

ISS Expedition Duration
March 2010 - March 2011

Expeditions Assigned

Previous Missions
21/22 is the first Expedition for the SODI-Colloid investigation.

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Experiment Description

Research Overview

  • One of the most promising applications of colloidal engineering is the fabrication of photonic devices. These devices must possess structures whose scale length is comparable to the wavelength of light, and that are ordered in three dimensions.

  • Unfortunately gravity plays a disturbing role. Sedimentation causes the tips of growing crystals to break, limiting crystal size and greatly modifying their morphology. This deleterious effect is exacerbated when producing binary colloidal crystals using particles of mixed materials, the ones having most promise for applications.

  • Selectable Optical Diagnostics Instrument - Advanced Photonic Devices in Microgravity (SODI-Colloid) seeks to study the properties of a peculiar, solvent mediated aggregation of colloidal particles.

The focus of Selectable Optical Diagnostics Instrument - Aggregation of Colloidal Solutions (SODI-Colloid) is on materials that have a special interest in photonics, with emphasis on nano-structured, periodic dielectric materials, known as photonic crystals, which possess appealing properties and make them promising candidates for new types of optical components. Since the key property of photonic crystals lies in the periodic variation of refractive index in two or three dimensions on a length scale that is equivalent to that of visible wavelength, the building block are (often mixtures of) colloidal particles of micrometric dimension. SODI-Colloid will study aggregation phenomena of colloidal systems, trying to tackle the puzzling and still not fully understood mechanisms of this phenomenon, with the benefit of a reduced gravity environment. Within such framework, the experiment here proposed is focused on a peculiar type of aggregation that received quite recently a notable interest in the scientific community. The system is composed of spherical colloidal particles suspended in a solution of two coexisting phases in near critical conditions. The interest of such a configuration lies in the fact that, in the homogeneous phase, the adsorption of one of the two species depends on temperature that is on the distance from the critical point. The exact nature of the interaction is still debated. According to the classical picture, the preferential adsorption of one component on the colloidal particles modifies the interparticle interaction, by weakening the repulsive contribution of surface charges. The resulting stability is strongly perturbed, turning from repulsive to attractive as soon as the distance from the two phase region is approached. The advantage of this system lies in the fact that the interparticle interaction is tuneable by controlling a macroscopic parameter such as the temperature. The specific goal of the SODI-Colloid experiment is to observe nucleation and the early stages of aggregation, where the first nuclei with supercritical size are formed, studying the growth rate and size distribution over time.

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Space Applications
The colloidal engineering process will contribute to the creation of new materials and products in space.

Earth Applications
SODI-Colloid will improve such colloids as paints, food products, drug delivery systems and ceramics by providing a better understanding of colloidal behavior.

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Operational Requirements and Protocols
Downlink of data is required to quickly assess the integrity of the liquid sample and to characterize the presence of aggregates in the sample volume. The structure of the aggregates will be measured by Near Field Scattering
Crewmembers will install the SODI ancillary equipment and the Colloid experiment container (equipped with 1 array consisting of 5 cells). After installation, the next steps consist of the optical processing of the experimental cells followed by probing the phase diagram near the critical point and observing the aggregation mechanisms of colloidal particles by way of the Near-Field Scattering optical technique. After processing the Colloid cells, the SODI instrument should be stowed.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Results Publications

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Ground Based Results Publications

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ISS Patents

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Related Publications

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Related Websites
ESA E-USOC Summaries

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