Use of the microgravity environment aboard the space station for microencapsulation experiments was a necessity before the ability to develop an Earth-based technology for making these microcapsules. “The technique that we have for making these microcapsules could not be done on the ground, because the different densities of the liquids would layer,” explained Dennis Morrison, Ph.D., retired NASA principal investigator of the Microencapsulation Electrostatic Processing System-II (MEPS-II) study and current vice president and director for microencapsulation research and development at NuVue Therapeutics, Inc. “But in space, since there is not sedimentation due to gravity, everything goes spherical.”
In space, surface tension shapes liquids into spheres. Each molecule on a liquid’s surface is pulled with equal tension by its neighbors. The closely integrated molecules form into the smallest possible area, which is a sphere. In effect, the MEPS-II system allowed a combination of liquids in a bubble shape because surface tension forces took over and allowed the fluids to interface rather than sit atop one another.
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