Soft robots are becoming one of the most exciting technologies of the future. Unlike traditional robots made from rigid metal parts, soft robots are flexible, lightweight, and can safely interact with people and delicate objects. They have the potential to transform industries such as healthcare, manufacturing, agriculture, disaster response, and even space exploration.
However, one major challenge has remained unsolved: how can soft robots change their shape easily, precisely, and efficiently without becoming stiff or difficult to control?
Now, researchers led by Wu and team have introduced an innovative solution inspired by one of mathematics' most fascinating shapes—the Möbius strip. Their invention, called the Pneumatic Torsion Strip (PTS), offers a completely new way for soft robots to bend, curl, and transform their shape. Using this technology, the researchers even created a meter-scale transformable carpet weighing about 2 kilograms that curls like the tendrils of climbing plants.
The breakthrough could lead to a new generation of smarter, larger, and more adaptable soft robots.
Why Shape-Changing Matters
Nature is full of living things that constantly change shape.
Plants curl around supports, vines wrap themselves around trees, octopus arms bend in every direction, and human muscles contract smoothly to create movement.
Scientists have long wanted robots to copy these natural movements because flexible robots are much safer and more adaptable than rigid machines.
Shape-changing technology is especially important for soft robotics because these robots often need to:
Grip objects of different sizes
Crawl through narrow spaces
Lift delicate materials
Change direction smoothly
Adapt to changing environments
Creating these movements efficiently has been one of the biggest engineering challenges.
The Problem with Existing Soft Robots
Most soft robots today use air pressure to move.
Small air chambers are built inside soft materials. When air is pumped into these chambers, they expand. Different parts expand by different amounts, causing the robot to bend.
Although this method works, it has several limitations.
As more air enters the robot:
The material stretches.
The robot becomes stiffer.
Bending becomes harder.
The amount of curvature is limited.
Because bending depends on stretching different layers by different amounts, engineers must carefully design wall thickness and stiffness before manufacturing. Once built, changing the bending direction or behavior is difficult.
Extreme movements such as tightly curling into loops are especially challenging.
Researchers wanted a completely different approach.
Inspiration from the Möbius Strip
The answer came from an unusual mathematical object known as the Möbius strip.
A Möbius strip is created by taking a ribbon, twisting it by 180 degrees, and joining the two ends together.
The result is a fascinating surface with only one continuous side.
Besides being famous in mathematics, the Möbius strip naturally stores elastic energy because of its twisted shape.
The research team wondered:
Could this stored energy be used to bend soft robots instead of stretching them?
That simple question led to the development of the Pneumatic Torsion Strip.
What Is a Pneumatic Torsion Strip?
The Pneumatic Torsion Strip (PTS) is surprisingly simple.
Instead of using complicated internal chambers, researchers take a flexible inflatable tube, bend it, and twist it into a ribbon-like shape.
When air is pumped inside:
The strip stores elastic energy.
That stored energy creates rotational force (torque).
The torque bends the soft robot.
Rather than stretching the robot itself, the strip acts like a built-in spring that gently pulls the robot into a new shape.
This creates smooth, controlled bending.
A Completely Different Way to Bend
Traditional soft robots bend because different layers stretch by different amounts.
The new Pneumatic Torsion Strip works differently.
Instead of creating unequal stretching, it applies rotational torque directly to the robot.
This difference brings several major advantages.
The robot keeps its original flexibility because the body itself is not being stretched.
The bending can occur almost anywhere along the robot.
Large bending angles become possible.
Even complex shapes can be created with relatively simple construction.
This opens entirely new possibilities for soft robotic design.
Adjustable Movement
One of the most impressive features of the new system is that its movement is highly adjustable.
Researchers discovered that the amount of bending depends on two main factors:
The geometry of the twisted strip
The internal air pressure
Increasing air pressure increases the strip's stored elastic energy.
More stored energy means greater bending force.
By carefully controlling air pressure, engineers can control:
How much the robot bends
How fast it bends
The final shape it reaches
This provides far greater control than many existing pneumatic systems.
No Complex Manufacturing Required
Many advanced soft robotic materials require expensive manufacturing techniques.
Some rely on magnetic particles.
Others require special temperature-sensitive materials.
Many involve complicated multi-layer construction.
The Pneumatic Torsion Strip avoids most of these challenges.
It can be created simply by twisting and bending a flexible inflatable tube.
This simplicity makes the technology attractive for building larger robots while keeping manufacturing costs relatively low.
Positive and Negative Torsion Strips
Researchers also developed two different versions of the strip.
These include:
Positive Pneumatic Torsion Strip (PPTS)
Negative Pneumatic Torsion Strip (NPTS)
By arranging these strips in different patterns, engineers can create various movements.
Soft structures can:
Bend upward
Bend downward
Curl
Contract inward
Form wave-like shapes
This makes the technology extremely versatile.
A Carpet That Moves Like Nature
Perhaps the most eye-catching demonstration is the team's meter-scale transformable carpet.
The carpet weighs approximately 2 kilograms yet can curl upward much like the tendrils of climbing plants searching for support.
Instead of relying on rigid motors or complicated joints, the carpet changes shape smoothly using Pneumatic Torsion Strips.
This demonstration shows that the technology can work not only in tiny laboratory devices but also in much larger structures.
Large-scale soft robots have traditionally been difficult to build because existing bending methods become less efficient as size increases.
The new approach may overcome many of those limitations.
Artificial Muscles
The researchers also demonstrated artificial muscles using the same concept.
Instead of copying biological muscles directly, these artificial muscles transform from a flat shape into a wavy shape during operation.
This movement produces contraction similar to muscle action.
Such systems could someday power wearable robots, medical devices, or flexible robotic arms.
Where Could This Technology Be Used?
The potential applications are extensive.
Future soft robots using Pneumatic Torsion Strips could be used in:
Medical robots that safely interact with patients
Search-and-rescue robots moving through collapsed buildings
Agricultural robots handling delicate crops
Industrial automation
Wearable robotic assistance
Flexible manufacturing systems
Micro-robotics
Space exploration
Adaptive furniture and smart materials
Because the technology scales well, it may be useful in both very small and very large robotic systems.
Challenges Still Remain
Although the results are promising, the technology is still in its early stages.
The researchers identified several areas needing improvement.
Currently, many strips are made from low-density polyethylene (LDPE) tubes.
At high air pressures or when carrying heavy loads, these tubes can develop creases that reduce performance.
Thicker materials help, but they also affect flexibility.
The team is also experimenting with thermoplastic polyurethane (TPU), which may provide greater durability.
Future Improvements
Researchers hope to improve manufacturing using advanced 3D printing technologies.
Future methods may include:
SLA 3D printing
Direct Ink Writing (DIW)
Programmable material structures
Automated assembly instead of manual construction
These techniques could allow engineers to fine-tune material properties during printing, making Pneumatic Torsion Strips even more precise and customizable.
The team also plans to explore miniature versions for micro-soft robots, although manufacturing such tiny structures presents additional challenges.
A New Direction for Soft Robotics
The Pneumatic Torsion Strip represents a fresh way of thinking about robotic movement.
Instead of forcing soft materials to bend through uneven stretching, it uses stored elastic energy to apply controlled rotational force directly where it is needed.
The design is simple, scalable, and highly adaptable.
Its ability to create large bending angles without significantly increasing stiffness could solve one of the biggest limitations of today's pneumatic soft robots.
From artificial muscles to shape-changing carpets that curl like plant tendrils, the demonstrations show that this technology is more than just a laboratory concept—it is a promising platform for future robotic systems.
As researchers continue improving materials, manufacturing techniques, and automation, Pneumatic Torsion Strips could become an important building block for the next generation of flexible, intelligent, and nature-inspired robots.
Reference: Wu, C., Liu, H., Lin, S. et al. Shape morphing of soft robotics by pneumatic torsion strip braiding. Nat Commun 16, 3787 (2025). https://doi.org/10.1038/s41467-025-59051-3
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