Researchers at the University of Chicago Pritzker School of Molecular Engineering have demonstrated for the first time how to use a type of material called a liquid crystal to build the basic pieces needed for logic operations, clearing the way for a completely new manner of computing.
The findings, which were published in Science Advances on February 23, are unlikely to lead to the development of transistors or computers in the near future, but they could pave the way for novel sensing, computing, and robotics systems.
“We showed you can create the elementary building blocks of a circuit—gates, amplifiers, and conductors—which means you should be able to assemble them into arrangements capable of performing more complex operations,” said Juan de Pablo, the Liew Family Professor in Molecular Engineering and senior scientist at Argonne National Laboratory, and the senior corresponding author on the paper. “It’s a really exciting step for the field of active materials.”
The details in the defects
The goal of the study was to learn more about a type of material known as a liquid crystal. A liquid crystal’s molecules are elongated, and when packed together, they form an orderly structure similar to the straight rows of atoms in a diamond crystal—but instead of being fixed in place like a solid, this structure can move around like a liquid. Liquid crystals, for example, are in the LCD TV you may already have in your home or in the screen of your laptop. Scientists are always looking for these kinds of oddities because they can use these unusual properties as the basis of new technologies.
Because of this strange molecular arrangement, there are locations in all liquid crystals where the ordered regions rub up against each other and their orientations don’t exactly match, resulting in “topological defects,” as scientists name them. As the liquid crystal flows, these dots shift about.
Scientists are intrigued by these defects, wondering if they could be used to carry information – similar to the functions that electrons serve in the circuits of your laptop or phone. But in order to make technology out of these defects, you’d need to be able to shepherd them around where you want them, and it’s proved very difficult to control their behavior. “Normally, if you look through a microscope at an experiment with an active liquid crystal, you would see complete chaos—defects shifting around all over the place,” said de Pablo.
But last year, an effort from de Pablo’s lab headed by Rui Zhang, then a postdoctoral scholar at the Pritzker School of Molecular Engineering, in collaboration with Prof. Margaret Gardel’s lab from UChicago and Prof. Zev Bryant’s lab from Stanford, figured out a set of techniques to control these topological defects. They showed that if they controlled where they put energy into the liquid crystal by shining a light only on specific areas, they could guide the defects to move in specific directions.
In a new paper, they took it a logical step further and determined that it should be theoretically possible to use these techniques to make a liquid crystal perform operations like a computer.
“These have many of the characteristics of electrons in a circuit—we can move them long distances, amplify them, and shut or open their transport as in a transistor gate, which means we could use them for relatively sophisticated operations,” said Zhang, now an assistant professor at the Hong Kong University of Science and Technology.
Though calculations suggest these systems could be used for computations, they are more likely to be uniquely useful in applications such as the field of soft robotics, the scientists said. Researchers are interested in soft robots—robots with bodies that aren’t made out of hard metal or plastic, but rather stretchy and soft materials—because their flexibility and gentle touch means they can perform functions that hard-bodied robots cannot. The team can imagine creating such robots that can do some of their own “thinking” using active liquid crystals.
They could also use topological flaws to transport small volumes of liquid or other materials from one location to another within tiny devices. “Perhaps one could conduct functions within a synthetic cell,” Zhang speculated. He believes that similar systems are already in use in nature to transport information and perform activities within cells.
“It’s not often that you are able to see a new way to do computing,” de Pablo said.