ACES researchers have for the first time, developed a smart textile from carbon nanotube and spandex fibres that can both sense and move in response to a stimulus like a muscle or joint.
“We have already made intelligent materials as sensors and integrated them into devices such as a knee sleeve that can be used to monitor the movement of the joint, providing valuable data that can be used to create a personalised training or rehabilitation program for the wearer,” Dr Foroughi said.
“Our recent work allowed us to develop smart clothing that simultaneously monitors the wearer’s movements, senses strain, and adjusts the garment to support or correct the movement,” he said.
The smart textile, which is easily scalable for the fabrication of industrial quantities, generates a mechanical work capacity and a power output which higher than that produced by human muscles.
It has many potential applications ranging from smart textiles to robotics and sensors for lab on a chip devices. The team, having already created the knee sleeve prototype, is now working on using the smart textile as a wearable antenna, as well as in other biomedical applications.
The new smart textile, described last month in the high ranking international journal, American Chemical Society (ACS Nano), was made possible through collaborations facilitated by ACES between researchers at the University of Wollongong and the University of Texas at Dallas.
ACES Director Prof. Gordon Wallace said the breadth of expertise required to enable fundamental materials science discoveries and their application into practical structures is enormous.
“It can only be done in a reasonable time frame within a culture like ACES that encourages the forging of appropriate research alliances,” Prof Wallace said.
“Materials that can provide both sensing and response capabilities are the holy grail of intelligent materials research. This fundamental discovery will find widespread application,” he said.
The discovery came three years into Dr Foroughi’s ARC Discovery Early Career Research Award (DECRA) project which aimed to create a new class of smart textile.
“Working with world-class scientists Prof Geoff Spinks and United States collaborator Prof Ray Baughman made it possible to create the first generation 3D carbon nanotube knitted smart textile,” Dr Foroughi said.
In recent years, researchers at The University of Texas at Dallas and colleagues at the University of Wollongong in Australia have put a high-tech twist on the ancient art of fiber spinning, using modern materials to create ultra-strong, powerful, shape-shifting yarns.
In a perspective article published Sept. 26 online in the Proceedings of the National Academy of Sciences, a team of scientists at UT Dallas’ Alan G. MacDiarmid NanoTech Institute describes the path to developing a new class of artificial muscles made from highly twisted fibers of various materials, ranging from exotic carbon nanotubes to ordinary nylon thread and polymer fishing line.
Because the artificial muscles can be made in different sizes and configurations, potential applications range from robotics and prosthetics to consumer products such as smart textiles that change porosity and shape in response to temperature.
“We call these actuating fibers ‘artificial muscles’ because they mimic the fiber-like form-factor of natural muscles,” said Dr. Carter Haines BS’11 PhD’15, associate research professor in the NanoTech Institute and co-lead author of the PNAS article, with research associate Dr. Na Li. “While the name evokes the idea of humanoid robots, we are very excited about their potential use for other practical applications, such as in next-generation intelligent textiles.”
Science Based on Ancient Art
Spinning animal fur and plant fibers to make thread and yarn goes back thousands of years. Aligning the fibers and then twisting them into yarn gives the yarn strength.
By exploiting this concept, and adding 21st-century science, the UT Dallas researchers have produced actuating muscle yarns that, like their wooly counterparts, can be woven, sewn and knitted into textiles.
For example, carbon nanotubes are essentially tendrils of tiny, hollow tubes that are super-strong and electrically conductive. In 2004, led by Dr. Ray Baughman, director of the NanoTech Institute and the Robert A. Welch Distinguished Chair in Chemistry at UT Dallas, the team developed a method to draw “forests” of nanotubes out into sheets of aligned fibers — much like carded wool — and then twist the sheets into yarns.
When heated and cooled, spiral-shaped artificial muscles expand and contract back and forth.
Next, the group turned to polymer fibers such as nylon sewing thread and fishing line, which consist of many individual molecules aligned along the fiber’s length. Twisting the thread or fishing line orients these molecules into helices, producing torsional — or rotational — artificial muscles that can spin a heavy rotor more than 100,000 revolutions per minute.
When these muscles are so highly twisted that they coil like an over-twisted rubber band, they can produce tensile actuation, where the muscle dramatically contracts along its length when heated, and returns to its initial length when cooled. That research, published in 2014, showed that simple, low-cost muscles made from fishing line can lift 100 times more weight and generate 100 times higher mechanical power than a human skeletal muscle of the same length and weight.
“The success of our muscles derives from their special geometry and the fact that we start with materials that are anisotropic — when they are heated, the materials expand in diameter much more than they expand along their length,” said Baughman, senior author of the PNAS perspective. This anisotropy is an intrinsic property of high-strength polymer fibers, and is the same principle that drives powerful artificial muscles the researchers discovered in 2012, which they made by adding a thermally responsive “guest” material within a carbon nanotube yarn.
“When these fibers are then twisted and coiled, their internal geometry changes so that when they are heated, that diameter expansion results in a change in length,” Baughman said. “The fiber’s diameter only has to expand by about 5 percent to drive giant changes in length.”
The Latest Twist
In their most recent experiments, described for the first time in the PNAS article, Haines and Li added a new twist to their artificial muscles.
“The coiled artificial muscles we initially made from fishing line and nylon sewing thread were limited in the amount they could expand and contract along their length,” Haines said. “Because of their geometry — like a phone cord — they could only contract so far before the coils began to collide with one another.”
The solution: Form the coiled actuators into spirals.
“The advantage to the spiral shape is that now our muscle can contract into a flat state, expand out in the other direction, and return to its original length, all without getting stuck on itself,” Li said. “Our experiments to date have been proof-of-concept, but have already shown that we can use heating and cooling to drive this back-and-forth motion across a giant range. This type of telescoping actuator can produce over an 8,600 percent change in length, compared to around 70 percent for our previous coils.”
Li said one potential application for the spiral-shaped coil might be thermally responsive clothing. Instead of a down-filled jacket, a coat that incorporates many small coils could change the loft and insulating power of the garment in response to temperature.
In the laboratory, Haines and Li have produced spools of coiled polymer muscle threads suitable for sewing. “We have shown that these thermally responsive fibers can be used in conventional machines, such as looms, knitting machines and sewing machines,” Li said. “As we move forward with our research, and scale it up, we hope to incorporate our ideas into functional fabrics and textiles for a variety of purposes, from clothing to environmentally responsive architecture to dynamic art sculptures.”
The University of Wollongong (commonly referred to as the Wollongong University), abbreviated as UOW, is a public research university located in the coastal city of Wollongong, New South Wales, Australia, approximately 80 kilometres south of Sydney.
As of 2012, the University had a total of 30,516 students enrolled, included 11,440 international students from more than 140 countries. The University ranked 276th in the 2013 QS World University Rankings, 276-300th in the 2013-2014 Times Higher Education World University Rankings, and 301-400th (352nd) in the 2013 Academic Ranking of World Universities.
The University of Wollongong has fundamentally developed into a multi-campus institution, three of which are in the Illawarra (Wollongong, Shoalhaven and Innovation), one in Sydney and one in Dubai, United Arab Emirates. The Wollongong Campus, the University’s Main Campus, is on the original site five kilometres north-west of the city centre, and covers an area of 82.4 hectares with 94 permanent buildings including six student residences. In addition, there are University Education Centres in Bega, Batemans Bay, Moss Vale and Loftus as well as the Sydney Business School in the City of Sydney. The University also offers courses equally based on the main Wollongong Campus in collaboration with partner institutions in a number of offshore locations including Singapore, Malaysia and Hong Kong.
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