Scientists from the Advanced Robotics Research Center at the Korea Institute of Machinery and Materials (KIMM) have developed a new process to weave ultra-thin fibers of shape-memory alloy (SMA) into fabric artificial muscles, enabling wearable robotic clothing that tests have shown can increase the wearer’s strength and reduce muscle load by up to 40%.
Although wearable robots designed with the new fabric-weaving process are currently limited to the laboratory phase, the KIMM research team behind the breakthrough method is already working on prototype designs for individuals suffering from strength and mobility limitations, with the ultimate goal of finding a commercial partner to bring their super-strength fabric manufacturing process to the wider marketplace.
Current Wearable Robot Technologies Face Severe Limitations
In an email to The Debrief, Dr. Cheol Hoon Park, Principal Researcher at KIMM’s Advanced Robotics Research Center and the leader of the wearable robot project, explained that many countries are entering a “super-aged” phase of society, and the demand for wearable robot technology that can increase strength and mobility is expected to dramatically increase.
However, Dr. Park noted that for such technologies to become more widely available, the limitations of current technologies must be overcome.
“They must be lightweight, comfortable to wear, and affordable,” the project leader explained.
For example, conventional wearable robots designed to provide strength and support to multiple joints, such as the shoulder, elbow, and wrist, rely on heavy, noisy motors or pneumatic actuators. The research team noted that these components make systems bulky, expensive, and uncomfortable to wear, especially during extended use. The answer has been an increased reliance on simpler, single-joint, wearable robots. Still, assisting large, complex joints like the shoulder has remained a major obstacle.
Now, Dr. Park and the KIMM team said they’ve created a system for weaving fabric muscles into fabric, resulting in a scalable method for mass-producing wearable-robot clothing that is quiet, streamlined, easy to use, and consumes very little power.
Heat From a Battery Pack Causes Artificial Muscle Fibers to Contract
Instead of air-powered actuators or bulky electric motors that add power to human muscles and joints, Dr. Park’s team created fabric muscles using small fibers of a material called shape-memory alloy. SMAs are materials that regain their original shape when exposed to elevated temperatures or pressures.
For this application, the team used an SMA wire with a diameter of 25 μm, or roughly one-fourth the width of a human hair. Next, the KIMM team processed the individual wires into coil-shaped ‘yarn.’ Like traditional yarn, this SMA yarn can enable the continuous weaving of fabric muscles.
When asked by The Debrief how their fabric muscle wearable robot works, Dr. Park explained that the SMA coil fibers that make up the muscles contract when heated to “about 40–50 °C.” However, he notes, the user is unlikely to notice the material being heated, so it can exert a directional force to assist muscle movement and reduce joint load, “thanks to an insulating fabric layer.”
“Like human muscles, the fabric muscle contracts as it heats up and relaxes as it cools down,” Dr. Park told The Debrief. “Cooling fans are not required when the user simply holds a load, but for repetitive lifting tasks, faster cooling is needed, so the fans help accelerate the process.” Park added that fans can be integrated in future consumer versions of the jacket, “depending on the use case.”
The wearable robot is powered by a 200 g battery pack mounted on the back of the jacket, which also includes a compact controller to change settings. Park said that the contraction force exerted by the fabric muscles can be altered by changing “the amount and duration of electric current” supplied to the system’s SMA fibers.
Depending on the setting level the user selects and their activity level, Dr. Park told The Debrief that the system “can typically operate for about four hours on a single charge.”
Tests Show 40% Reduced Muscle Effort and 57% Increase in Range of Motion
According to the team’s announcement, the KIMM team’s prototype wearable robot, a jacket with the SMA fiber muscles built in, was able to simultaneously assist the wearer’s elbow, shoulder, and waist. Tests showed that the less-than-2-kilogram jacket reduced muscle effort by more than 40% during repetitive physical tasks. Notably, the 10g of wearable robot fabric at the core of the system can light 10-15 kilograms (22-33 lbs.)
A more complex shoulder-assist, wearable robot weighing just 840 grams (less than 2 pounds), tested in clinical trials at Seoul National University Hospital (SNUH) on patients with muscular weakness, including those with Duchenne muscular dystrophy, improved average shoulder movement range by over 57%.
When discussing the next phase of development, Dr. Park told The Debrief that they are currently “developing and evaluating a prototype of the clothing-type wearable robot in the form of pants.”
“We expect that it could help people who have difficulty walking on slopes or stairs, or standing for long periods of time,” the project leader explained.
Wearable Robot Clothing Could Reach the Market Within 1-2 Years After Agreement
Although the current version of the wearable is not yet commercially available, Dr. Park noted that the core technology for weaving SMA fibers into fabric muscles was developed at a non-profit research institute, “so it will need to be transferred to an industrial partner for commercialization.”
We have already developed both the manufacturing equipment for mass-producing the fabric muscle — the core component — and a working prototype of the wearable robot,” he added.
Although there is no pending agreement with a commercial partner to date, Dr. Park told The Debrief that once they transfer their technology to a commercial partner, they expect it could reach the commercial market “within one to two years.”
Although there are potential uses for the team’s fiber muscle-weaving process, including enhanced strength “super soldiers,” Dr. Park told The Debrief, “We hope that the fabric muscle we developed—and the clothing-type wearable robot based on it—will help make wearable robotics more accessible and ultimately improve the quality of life for many people.”
The paper “Soft Exosuit Based on Fabric Muscle to Assist Shoulder Joint Movements in Patients With Neuromuscular Diseases” was published in IEEE Transactions on Neural Systems and Rehabilitation Engineering.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.