Researchers at Arizona State University are creating bio-inspired robotic “muscles” that could let robots function in extreme conditions—like boiling water and rough surfaces—overcome obstacles that stop traditional motor-driven machines, and still lift up to 100 times their own weight. These next-generation robots are expected to be lighter, more compact, and free from direct power connections.
Eric Weissman, a doctoral student in ASU’s Robotic Actuators and Dynamics Lab, led a study titled “Versatile Artificial Muscles by Decoupling Anisotropy,” published in Proceedings of the National Academy of Sciences. The lab’s director, Jiefeng Sun, also contributed as a co-author.
“We essentially created a new type of artificial muscle that replicates how real muscles work,” Weissman explained. “Although bio-inspired muscles already existed, ours are more adaptable, lighter, and stronger.”
Bio-Inspired HARP Actuators
Conventional quadruped robots often face mobility challenges because they rely on motors, making them bulky and less flexible.
In contrast, Weissman’s helical anisotropically reinforced polymer (HARP) actuators imitate the way natural muscles contract and expand. Lightweight, flexible, and quiet, they lift far more than comparable electric systems.
“These muscles resemble small tubes coiled like cavatappi—a hollow, ridged, corkscrew-shaped pasta,” Weissman said. “When we pump in a bit of air, they expand and contract.”
“Thanks to their versatility and adaptability, we were able to greatly reduce the required pressure, allowing us to build a robot that can walk on its own without an external power source, carrying everything it needs,” Weissman said.
From Disaster Response to Everyday Assistance
The team’s work goes beyond creating bio-inspired muscles for single, specialized tasks. Instead, they’ve developed a flexible framework that can be customized for a variety of more affordable applications.
“In disaster response, soft robots could navigate debris or collapsed structures to locate survivors. Their flexible bodies let them squeeze into tight spaces without causing additional damage,” Weissman explained. “At home, they could help older adults with tasks like reaching items or doing simple chores.”
HARP actuators can endure extreme heat, making them suitable for industrial rinsing or collecting samples near ocean thermal vents. Their flexibility, along with their ability to rotate and grip, also makes them well suited for agricultural and industrial tasks.
The team has filed a provisional patent through ASU’s Skysong Innovations.
Bionic elephant arm extends above, around, and beneath
Another project in Sun’s lab is doctoral student Jiahe Wang’s “bionic elephant arm,” a soft robotic arm modeled on the dexterity and flexibility of an elephant trunk.
This bio-inspired arm can easily reach over, under, and around obstacles, making it ideal for inspection and manipulation tasks in industrial environments. Its lightweight, compliant design minimizes the risk of damaging equipment and enhances safety for workers, especially in situations requiring close human-robot interaction.
“In chemical plants or busy production lines, equipment is often hard to access and sensitive to accidental contact. Even routine inspections can force operations to pause, resulting in costly downtime,” Wang explained.
In agriculture, a slimmer version could navigate through plants to assist with pollination—a task that typically demands long hours of manual labor. Unlike drones, which can disturb crops with strong airflow, a soft robot can perform the work more gently.
Heavier-duty versions could be deployed in space to assist astronauts with maintenance tasks or tool handling. Its softness and flexibility let the robot operate safely around people and delicate equipment.
“Crops such as strawberries and tomatoes have dense foliage that’s difficult for pollinators to move through,” Sun explained. “A soft robotic arm can navigate these obstacles and carry out pollination effectively.”
A novel type of backup
Doctoral student Rohan Khatavkar developed a back support device to ease heavy lifting. It can also support individuals with weak back muscles and help prevent falls.
“Traditional active BSDs rely on motors and can be adjusted for specific tasks,” Khatavkar said. “But they tend to be bulky and heavy, which can be uncomfortable, especially for those with physical limitations. Passive devices are lighter and more compact, but they can’t be fine-tuned for different tasks.”
Khatavkar’s latest BSD combines active and passive elements in parallel, using an elastic actuator and a pneumatic artificial muscle to create a tunable system.
“The updated device is compact and lightweight while allowing adjustable assistive force tailored to specific tasks,” he explained. “The soft design is lighter and includes adjustable stiffness and force that can be turned off when not needed.”
Integrating it all for the future
Sun envisions countless applications for these bio-inspired muscles across fields such as agriculture, industry, health care and surgery, household and landscaping tasks, and even space exploration in the near future.
“Ultimately, these softer, flexible, and compliant muscles can be integrated into a wide variety of robots because they are smaller, lighter, and safer than today’s rigid machines, which pose pinching hazards,” Sun said.
“By incorporating space-grade materials, we can create devices that offer enhanced mobility, agility, and smooth movement for both astronauts and the robots they use in space.”
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