An interdisciplinary team of University of Pennsylvania researchers has already developed a technique for controlling liquid crystals by means of physical templates and elastic energy, rather than the electromagnetic fields that manipulate them in televisions and computer monitors. They envision using this technique to direct the assembly of other materials, such as nanoparticles.
Now, the Penn team has added another tool to its directed assembly toolkit, developing a new kind of template for rearranging particles and a new set of patterns that can be formed with them.
The team consists of Kathleen Stebe, the School of Engineering and Applied Science's deputy dean for research and professor in Chemical and Biomolecular Engineering; Randall Kamien, professor in the School of Arts and Sciences' Department of Physics and Astronomy; and Shu Yang, professor in Engineering's departments of Materials Science and Engineering and Chemical and Biomolecular Engineering. Members of their labs also contributed to the new study, including lead author Marcello Cavallaro Jr., Mohamed Gharbi, Daniel Beller, Simon Čopar, Zheng Shi and Tobias Baumgart.
Their work was published in the Proceedings of the National Academy of Science.
Crystals are materials that have molecules arrayed in regular three-dimensional patterns; liquid crystals contain some but not all of these patterns, and their molecules can flow around one another and change the direction they face. This behavior allows defects, places on the surface where the molecular orientation of the liquid crystals is disrupted.
Despite their name, such defects are highly desirable. If the location of the defects can be controlled, the change in pattern or orientation can be put to use. In a liquid crystal display, for example, the crystals' orientation in different regions determines which parts of the screen are illuminated.
In an earlier study, the t
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