In their new study, the researchers use nematic liquid crystal, which have less long-range order in their patterns but are the kind found in liquid crystal displays.
"These nematic structures are very reconfigurable. That's the basis of why they're good for displays," Stebe said. "Everyone knew that materials can be moved and positioned with electric and magnetic fields, but we're doing it with fields of elastic energy and showing that this technology can be used in assembling materials."
As in their previous experiments, the team started with a template consisting of microscopic posts that was then topped with the liquid crystal. In this experiment, however, instead of a pattern of defects forming only on the surface of the liquid crystal, a ring-shaped defect encircled each of the posts at their midpoints. This ring then acts like another template, directing the arrangement of patterns on the liquid crystal surface, more than 50 microns away.
"With the smectic liquid crystals," Kamien said, "the patterns of defects we could make were closely associated with the corners of the posts. With nematic liquid crystals, we can form these rings, which is a new way to tell what to go where."
"And we're showing," Yang said, "that, whether we use smectic or nematic crystals, we can use a template that directs these surface defect arrays, which can then hold things like colloids, nanoparticles or quantum dots."
Being able to control the spacing and arrangement of these secondary materials could allow for makin
|Contact: Evan Lerner|
University of Pennsylvania