An international research team led by University of Waterloo has innovated a new material designed to act as flexible “artificial muscles” for robots. This advancement aims to replace traditional rigid motors and pumps, enabling robots to move in a more natural and fluid manner. Unlike conventional hard robots, soft robots are adaptable and pliable, making them safer for interactions with humans. However, the materials currently utilized for their movement lack the necessary strength for effective operation.
The research group from Waterloo has discovered a method to significantly enhance the strength of smart, rubber-like materials. They achieved this by incorporating liquid crystals (LCs)—widely used in electronic displays and sensors—into liquid crystal elastomers (LCEs), which are regarded as promising building blocks for soft robotics.
Dr. Hamed Shahsavan, a professor of chemical engineering at Waterloo and the leader of the research team, stated, “What we call artificial muscles are essential for unlocking the true potential of soft robots. They allow robots to move flexibly, safely, and with precision, which is especially important for applications like micro-medical robots.”
LCEs possess the unique ability to undergo substantial shape changes in a reversible and programmable manner when subjected to heat. The research team found that by blending small quantities of LCs with LCEs, they could create materials that are significantly stiffer and up to nine times stronger. Shahsavan elaborated, “To put this in perspective, fibers from the new LCEs can, when heated, lift loads up to 2,000 times their own weight.” Additionally, these LCEs deliver an output work of nearly 24 J/kg, approximately three times the average work produced by mammalian muscles.
X-ray analysis revealed that the LCs disperse within the LCEs, forming small pockets similar to chocolate chips in cookie dough. While in a liquid state, these LC pockets surprisingly behave like solids, retaining their shape and enhancing the stiffness of the surrounding LCEs when pulled or stretched. The researchers anticipate that LCEs with these improved mechanical properties will play a pivotal role in the rapidly advancing field of soft robotics. This technology could enable a vast array of movements, from drug delivery within the human body to collaboration with humans in manufacturing settings.
Shahsavan remarked, “Materials with such capabilities are highly desired in robotics as they can replace outdated, bulky, heavy actuators and electromotors with lightweight, soft, artificial muscles without compromising performance. This represents the simplest yet most robust method to enhance the stiffness of LCEs while preserving their programmable nature.”
The international research team also includes Dr. Tizazu Mekonnen, a chemical engineering professor at Waterloo, along with engineering graduate students Sahad Vasanji and Matthew Scarfo. Additional contributors are Dr. M.O. Saed from the University of Cambridge and Dr. Antal Jakli from Kent State University. Researchers are now focusing on utilizing these new materials as 3D printing inks to fabricate artificial muscles on a larger scale. Their findings were recently published in the journal Advanced Materials.
