Shape-Changing Polymer Could Advance Soft Robots, Artificial Muscles

A team of scientists has created a new shape-changing polymer that could transform how future soft materials are constructed.

Made using a material called a liquid crystalline elastomer (LCE), a soft rubber-like material that can be stimulated by external forces like light or heat, the polymer is so versatile that it can move in several directions.

Its behavior, which resembles the movements of animals in nature, includes being able to twist, tilt left and right, shrink and expand, said Xiaoguang Wang, co-author of the study and an assistant professor in chemical and biomolecular engineering at The Ohio State University.

“Liquid crystals are materials that have very unique characteristics and properties that other materials cannot normally achieve,” said Wang. “They’re fascinating to work with.”

This new polymer’s ability to change shapes could make it useful for creating soft robots or artificial muscles, among other high-tech devices in medicine and other fields.

Today, liquid crystals are most often used in TVs and cell phone displays, but these materials often degrade over time. But with the expansion of LEDs, many researchers are focused on developing new applications for liquid crystals.

Unlike conventional materials that can only bend in one direction or require multiple components to create intricate shapes, this team’s polymer is a single component that can twist in two directions. This property is tied to how the material is exposed to temperature changes to control the molecular phases of the polymer, said Wang. 

“Liquid crystals have orientational order, meaning they can self-align,” he said. “When we heat the LCE, they transition into different phases causing a shift in their structure and properties.”   

This means that molecules, tiny building blocks of matter, that were once fixed in place can be directed to rearrange in ways that allow for greater flexibility. This aspect may also make the material easier to manufacture, said Wang.

The study was recently published in the journal Science.

If scaled up, the polymer in this study could potentially advance several scientific fields and technologies, including controlled drug delivery systems, biosensor devices and as an aid in complex locomotion maneuvers for next-generation soft robots.  

One of the study’s most important findings reveals the three phases that the material goes through as its temperature changes, said Alan Weible, co-author of the study and a graduate fellow in chemical and biomolecular engineering at Ohio State. Throughout these phases, molecules shift and self-assemble into different configurations.   

“These phases are one of the key factors we optimized to allow the material ambidirectional shape deformability,” he said. In terms of size, the study further suggests that the material can be scaled up or down to adapt to nearly any need.

“Our paper opens a new direction for people to start synthesizing other multiphase materials,” said Wang.

Researchers note that with future computational advances, their polymer could eventually be a useful tool for dealing with delicate situations, like those that require the precise design of artificial muscles and joints or upgrading soft nanorobots needed for complex surgeries.

“In the next few years, we plan to develop new applications and hopefully break into the biomedical field,” said Weible. “There’s a lot more we can explore based on these results.”

Reference: Yao Y, Wilborn AM, Lemaire B, et al. Programming liquid crystal elastomers for multistep ambidirectional deformability. Science. 2024;386(6726):1161-1168. doi: 10.1126/science.adq6434

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