"The first layer's molecules tend to be pinned to the edges of the posts," Kamien said, "so changing a post's size and shape will change how many defects can sit on its edges at the same time."
The size discrepancy between the posts and individual molecules of the liquid crystal is also a key feature for using this class of liquid crystal in directed assembly. The posts are each a few microns wide and tall, still microscopically small, but large enough to be easily and economically made to specification. This is much more attractive than trying to directly control the size and arrangement of the liquid crystals' defects.
"The liquid crystal layers are very thin, so the defects are on the order of several nanometers across" Kamien said. "Those defects would normally be very hard to control, especially compared to the posts, which are more like a few thousand nanometers across."
Beyond sensors and displays, these defects can be used in nanomanufacturing.
"If you make defects like dimples, you could put ink in them and use them like a stamp," Kamien said. "Or you could make the inverse of the dimples and make points, which could be used as localized surface plasmon resonance hot spots for chemical and biological sensing or as a topographic protrusion for creating a superhydrophobic surface."
And because the layers of liquid crystals transmit elastic energy, they can also be used to do mechanical work. This means that the top layer could be used as a template to assemble even larger molecules.
"You could put nanoparticles, quantum dots or carbon nanotubes in the liquid cry
|Contact: Evan Lerner|
University of Pennsylvania