An international research team led by The University of Texas at Dallas has discovered that ordinary fishing line and sewing thread can be cheaply converted into artificial muscles made from nano tech yarn that can lift 100 times more weight and generate 100 times higher mechanical power than human muscles of the same length and weight. Per weight, these synthetic muscles can generate 7.1 horsepower per kilogram, about the same degree of “volumetric efficiency” as a jet engine.
Twisting together a bundle of polyethylene fishing lines, whose total diameter is only about 10 times larger than a human hair, produces a coiled polymer muscle that can lift 16 pounds. Operated in parallel, similar to how natural muscles are configured, 100 of these polymer muscles could lift about 1,600 pounds.
Scientists at UT Dallas’ Alan G. MacDiarmid NanoTech Institute teamed with scientists from universities in Australia, South Korea, Canada, Turkey and China to accomplish the advances.
A UT Dallas release notes that the artificial muscles are powered thermally by temperature changes. They contract lengthwise when heated and return to initial length when cooled. Compared to natural muscles, which contract by only about 20 percent, these new muscles can contract by about 50 percent of their length. The muscle strokes also are reversible for millions of cycles as the muscles contract and expand under heavy mechanical loads.
Heat to induce contraction can be produced electrically, by absorption of light or by the chemical reaction of fuels. The polymer muscles are normally electrically powered by resistive heating using the metal coating on sewing thread or by using metal wires that are twisted together with the muscle. For other applications, however, the muscles can be self-powered by environmental temperature changes, says Carter Haines, lead author of the study.
“We have woven textiles from the polymer muscles whose pores reversibly open and close with changes in temperature. This offers the future possibility of comfort-adjusting clothing,” says Mr Haines, who started his research career in Dr. Baughman’s lab as a high school student doing summer research through the George A. Jeffrey NanoExplorers Program, which Dr. Baughman initiated. Mr. Haines earned an undergraduate physics degree (2011) from UT Dallas and is now a doctoral student in materials science and engineering.
The research team also has demonstrated the feasibility of using environmentally powered muscles to automatically open and close the windows of greenhouses or buildings in response to ambient temperature changes, thereby eliminating the need for electricity or noisy and costly motors.
Twisting the polymer fiber converts it to a torsional muscle that can spin a heavy rotor to more than 10,000 revolutions per minute. Subsequent twisting, so that the polymer fiber coils like a heavily twisted rubber band, produces a muscle that dramatically contracts along its length when heated, and returns to its initial length when cooled. If coiling is in a different twist direction than the initial polymer fiber twist, the muscles instead expand when heated.
On the opposite extreme, independently operated coiled polymer muscles having a diameter less than a human hair could bring lifelike facial expressions to humanoid companion robots for the elderly and dexterous capabilities for minimally invasive robotic microsurgery. Also, they could power miniature “laboratories on a chip,” as well as devices for communicating the sense of touch from sensors on a remote robotic hand to a human hand.
“The application opportunities for these polymer muscles are vast,” says corresponding author Dr. Ray, a professor of chemistry and the Robert A. Welch Distinguished Chair in Chemistry at UT Dallas and director of the NanoTech Institute. “Today’s most advanced humanoid robots, prosthetic limbs and wearable exoskeletons are limited by motors and hydraulic systems, whose size and weight restrict dexterity, force generation and work capability.” A gift from the Robert A. Welch Foundation in September 1998 created the chair, which is designed to encourage advancements in the field of chemistry in Texas. Dr. Baughman was appointed to the chair in September 2001.
Dr. Ray Baughman is a pioneer in the field of nanotechnology who was elected to the National Academy of Engineering in 2008, a year he was ranked 30th among the decade’s top 100 material scientists by Thomson Reuters. He is also a prolific inventor and scientist, holding more than 70 U.S. patents. In 2002 Dr. Baughman founded the above-mentioned NanoExplorers program, funded by the Robert A. Welch Chair grant, which promotes nanotechnology-based education for the next generation of scientists and brings promising high-schoolers like Carter Haines into UT Dallas labs and the world of nanotechnology. “One of the reasons I love research is the opportunity it provides to inspire students,” Dr. Baughman observes. “Our NanoExplorer high school students and our undergraduate and graduate students become knights of our NanoTech Institute, and use this opportunity to do exciting original research.”
Dr. Baughman named the program after Dr. George A. Jeffrey, a professor at the University of Pittsburgh, who once gave a high school-aged Baughman the chance to study in a lab. Dr. Baughman has bachelor’s degree in physics from Carnegie Mellon University (1964) and a doctorate in the materials science area from Harvard University (1971). Upon graduation he was employed by Allied Chemical, which later became AlliedSignal and then Honeywell. After 31 years in the industry, he became the Robert A. Welch Professor of Chemistry and
director of the NanoTech Institute in 2001.
Guided by theory and enabled by synthesis, the UT Dallas <a href=”http://nanotech.utdallas.edu/“>Alan G. MacDiarmid NanoTech Institute</a> develops new science and technology exploiting the nanoscale. Its researchers inspire students by creating an atmosphere of excitement, fun, and creativity. The Institute designs frontier science and technology by teaming globally, and providing a place where physicists, chemists, biologists, ceramicists, metallurgists, and mathematicians join in teams with engineers to solve problems, functioning as an engine of economic growth by eliminating boundaries that interfere with the transition from science to technology, and from technology to product.
Ray Baughman is a member of the National Academy of Engineering, The Academy of Medicine, Engineering and Science of Texas, a Fellow of the American Physical Society and the World Innovation Foundation, an Academician of the Russian Academy of Natural Sciences, an Honorary Professor of three universities in China, and is on editorial and advisory boards of Science, Synthetic Metals, the International Journal of Nanoscience, and the Encyclopedia of Nanoscience and Nanotechnology.
Dr. Baughman’s current research focuses in part on developing new technologies for harvesting and storing waste energy, new types of artificial muscles, the fabrication, characterization and application of carbon nanotube sheets and yarns, sensors, new material synthesis, and fundamental structure-properties relationships for materials.
Other UT Dallas NanoTech Institute researchers involved with the work are Dr. Shaoli Fang, associate research professor; Dr. Márcio Lima and Dr. Mikhail Kozlov, research scientists; Dr. Na Li, Dr. Mônica Jung de Andrade, Dr. Jiyoung Oh and Dr. Xavier Lépro, research associates; and Benjamin Swedlove, graduate research assistant.
International collaborators are Dr. Geoffrey M. Spinks, Dr. Javad Foroughi, Dr. Sina Naficy and Dr. Gordon G. Wallace from the University of Wollongong (Australia); Dr. Fatma Göktepe and Dr. Özer Göktepe from Namik Kemal University (Turkey); Shi Hyeong Kim and Dr. Seon Jeong Kim from Hanyang University (Korea); Seyed M. Mirvakili and Dr. John D. W. Madden from the University of British Columbia (Canada); and Xiuru Xu from Jilin University (China).
The research was principally funded by the U.S. Air Force Office of Scientific Research at Wright-Patterson AFB in Ohio, with additional funding from the Air Force; the Office of Naval Research at Arlington, VA, the Robert A. Welch Foundation, the Creative Research Initiative Center for Bio-Artificial Muscle, the Korea-U.S. Air Force Cooperation Program, the Australian Research Council, the Australian
National Fabrication Facility, a Canada Discovery grant, the China National 973 Project and NSF China.
The University of Texas at Dallas
The University of Texas at Dallas