Many recent advances in microtechnology and nanotechnology depend on microscopic spherical particles self-assembling into large-scale aggregates to form a relatively limited range of crystalline structures. Directed assembly is a new branch of this field, where scientists figure out how to make particles assemble to form a broad range of structures at given locations.
Current techniques for directed assembly typically use an applied field, such as an electric or magnetic field, to move particles and to assemble them into well-defined structures. Now, researchers at the University of Pennsylvania have identified a simple new method to direct particle assembly based only on surface tension and particle shape.
The research, led by Kathleen J. Stebe, professor in the Department of Chemical and Biomolecular Engineering and the school’s Deputy Dean for Research, was performed by a team of researchers in her laboratory, Marcello Cavallaro Jr., Lorenzo Botto, Eric P. Lewandowski and Marisa Wang. It was published in the Proceedings of the National Academy of Sciences.
Their results rely on the simple fact that a liquid surface will tend to minimize its surface area.
“It’s the same reason that surface tension makes a drop of water want to be a sphere,” Stebe said. “But we can tune that phenomenon to do astonishing things.”
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