Colloidal Gelatin (CGEL)

Objectives

The objective of this experiment was to study growth of binary colloidal alloy crystals, colloid-polymer gels and fractal colloidal gels by static and dynamic light scattering. Some supplementary photography was also planned. The primary goal of these experiments was to assist in optimizing sample choice for future experiments, Physics of Colloids in Space, scheduled to fly in the express rack on the International Space Station (ISS). The glovebox experiments help mitigate the risk of the ISS experiment.

Shuttle-Mir Missions
NASA-5

Approach
Three different types of colloids were investigated as a part of the CGEL experiment: binary alloy colloidal crystals, colloid polymer mixtures, and fractal colloid gels. The idea was to capture the behavior of the colloids on Mir by using photography and light scattering recording. But first, samples were homogenized at the beginning of the mission and prior to data collection. The fractal colloid gels involved mixing two different solutions on Mir. The experiment was conducted inside the glovebox facility. All light scattering results were not performed due to the loss in power on Mir due to the collision. However, extensive photographs were taken, primarily of colloid-polymer mixtures, and also of binary alloy colloidal crystals.

Results
Pictures of binary colloid alloys were obtained; pictures of colloid-polymer mixtures were obtained.

Unexpected structures were seen in the colloid-polymer mixtures. These structures suggest that the phase separation proceeds along different paths, that the crystals may grow out of the liquid in some instances, while out of the gas in other instances. Such results have never been observed on Earth because gravity leads to macroscopic phase separation, which obscures these results. These results have helped inspire new experiments, now planned primarily for PCS2.

Earth Benefits
The advantages of studying colloids in microgravity is the improvement of next generation development of light switches, displays, and optical devices to be used in computers and communications.

Publications
None available at this time.

Principal Investigators
Dave A. Weitz, Ph.D.
University of Pennsylvania

Co-Investigators
Prof. P.N. Pusey
Dr. P.N. Segre

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