Modern technologies are built from semiconductor-based integrated circuits that rely on electrons to perform computing operations. Demand has increased in recent years for wearable electronic devices and soft robots, but they still are controlled with conventional rigid circuits.

Researchers are working to find “active” materials that could transmit information like static circuits. “Liquid crystals” are one of the materials under investigation. 

A research team including scientists at Argonne National Laboratory and the University of Chicago published a study that shows how to design the basic elements needed for electronic computations by using liquid crystals.

“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,” Juan de Pablo, an Argonne scientist, said in a news release. “It’s a really exciting step for the field of active materials.”

Odd structural activity

You might already have liquid crystals in your TV or computer; they’re found in LCD screens. A liquid crystal is composed of elongated molecules that have some order when they’re packed together. But instead of being frozen in one place like in a solid, the molecules also can move around like a liquid.

This unusual molecular activity means that all liquid crystals have spots where the ordered sections bump into each other and the orientations don’t always match. Scientists call this a “topological defect.” The defects shift as the liquid crystal moves and are difficult to control.

“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,” de Pablo said.

Harnessing the chaos

Scientists are fascinated by these defects and believe they might be good information carriers for logic operations — if they can be controlled. 

Defects share characteristics with a circuit’s electrons, such as moving long distances and shutting or opening their transport functions like a transistor gate. In liquid crystals, the transport process occurs when chemical energy is converted to mechanical work.

The scientists discovered that one defect’s motion can be substantially helped or hindered by another defect. They used this concept to manipulate the defects into performing circuit-like functions. 

The research team came up with a set of techniques to control the defects by manipulating where energy enters a liquid crystal. They guided the defects in certain directions by shining a light only on specific areas of the liquid crystal. Researchers believe this action could allow liquid crystals to perform operations like a computer.

What’s next

This system could be used for computations, but the scientists believe the more likely near-term application is for use in robots made from soft, stretchy material. The liquid crystals could help the robots do some “thinking.” 

Defects also could move small amounts of liquid inside tiny devices. The concept could come in handy in synthetic cells.

The research team is working with partners on further experiments to confirm their findings. The study findings are not expected to immediately result in new computers or transistors. Instead, they uncover a technique on which to base new sensing, computing, and robotic technologies without conventional circuits and electrons.