Published: March 11, 2020 By

Researchers at CU Boulder found that when electricity is applied to ‘torons,’ they celebrate like they’re at carnival

Parades dancing through the streets are common during celebrations like Mardi Gras. And now, it may become more common in electronics like your smart phone too, thanks to newly published research from the University of Colorado Boulder.

These new findings, which were published today in the Proceedings of the National Academy of Sciences, demonstrate how when electricity is applied to thousands of microscopic honeycomb-shaped lattices of liquid crystal structures, called torons, they begin to “dance” while moving in the same direction, expanding and contracting, rotating, in response to the pulses.

This new behavior, which dovetails with previous research on schools of molecular “fish,” is one of the first such examples of movement in a system many thought until recently to be stationary. By “turning on the music,” these findings redefine what’s possible for this system, possibly changing the game for electronics that already rely on liquid crystals, such as smartphones, laptops and televisions, as well as for emerging fields that could rely on them in the future like artificial intelligence.

“What we saw was something fascinating because they move but they’re also rotating … it reminded us of carnival, where people are dancing, shaking their hands, rotating, and yet, with all of that motion, they’re still moving along the street,” said Ivan Smalyukh, a physics professor at CU Boulder and the study’s co-author.

“It’s interesting that this emergent phenomenon happens in a material that we all use in daily life.”

Liquid crystals—a staple in liquid-crystal display, or LCD, screens—became popular in technological devices because of their ability to interact with and alter light. These tiny crystals, though, are largely stagnant. They just stay in place, and that’s the only way they were thought that they could be used in electronics.

“Historically, people thought that you cannot have motion in crystals because you are required in a crystal to have this perfect ordering that is, by default, kind of incompatible with crystals,” said Smalyukh.

One day, however, when lead author Hayley Sohn was experimenting with new ways to create large groups of molecular deformations within liquid crystal solutions, she came across something unexpected: They moved.

At the time, the researchers realized they had not one but two interesting movement behaviors at play—one of which would become their already-published paper on “schooling.”

“We had these videos and these experiments in the same folder. We were planning on presenting it all together, and then we realized that something different was happening here that we didn’t quite understand, and so we put it on the back burner and then came back to it. And, you know, ended up with, I think, a really interesting new story that is distinctly different from that schooling, but it has a lot of kind of similar ideas,” said Sohn, who is a recently graduated PhD student from materials science and engineering in the CU Boulder College of Engineering and Applied Science.

Rather than a simple clustering like a school of fish when they applied electricity, they instead saw tens of thousands of toron crystallites move with the current as if they were attending a parade—a Mardi Gras parade, to be precise—with these liquid crystal structures spinning, morphing, stretching, dancing.

“Previously, we didn’t have so much really close interaction between the different structures, and here, they’re all connected in an interesting way that, as they’re morphing, all of the structure around them morph in a similar way,” said Sohn.

“It was really interesting to see and really surprising.”

And the researchers view this as only the beginning.

“It’s hard even to list all of the possibilities because when you have something new, you typically don’t know everything you can do with it,” said Smalyukh.

“In a sense, this is a new toy for the scientific and engineering community to play with and we still need to discover what we can do with it. We already know a lot, it looks great, we know that there are opportunities that did not exist, but the entire scope of what can be done with it still remains to be discovered.”