Tag Archives: artificial muscle

Scientists devise tiny robot insects that can’t be crushed by a flyswatter

In the future, swarms of tiny flying soft robots could zip through the sky, performing various tasks such as monitoring the environment, remote repairs, perhaps even pollination. In Switzerland, engineers have recently demonstrated a new type of insect-like flying robots that may do just that. But don’t let their fragile appearance deceive you — these tiny bots are so strong they can resist being battered by a flyswatter.

The DEAnsect. Credit: EPFL.

Central to the proper functioning of this tiny soft robot, known as DEAnsect, are artificial muscles. Researchers at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland fitted the thumbnail-sized robots with dielectric elastomer actuators (DEAs) — hair-thin artificial muscles — which propel the artificial insects at about 3cm/second through vibrations.

Each DEA contains an elastomer membrane sandwiched between two soft electrodes. When a voltage is applied, the electrodes come together, compressing the membrane; once the voltage is switched off, the membrane returns to its original size. Each of the robot’s legs has three such muscles.

The vibrations caused by switching the artificial muscles on and off (up to 400 times a second) allows the DEAnsect to move with a high degree of accuracy, as demonstrated in experiments in which the robots followed a maze (shown in the video).

These extremely thin artificial muscles allowed the entire design to be streamlined in a very compact frame. The power source only weighs 0.2 grams, while the entire robot, battery and other components included, weighs one gram.

“We’re currently working on an untethered and entirely soft version with Stanford University. In the longer term, we plan to fit new sensors and emitters to the insects so they can communicate directly with one another,” said Herbert Shea, one of the authors of the new study published in Science Robotics.

Folded actuators 1.

Artificial origami-inspired muscle can lift up to 1,000 times its own weight

The soft mechanism could open up whole new fields of robotics, from biodegradable systems and wearable bots to moving architecture.

Folded actuators 1.

Showcasing some simple motion sequences using the artificial muscles.
Image credits Li S., Vogt M. et al., 2017, PNAS.

Soft robotics has seen some amazing progress in the last few decades. This field of research is looking into how robots can benefit from less rigid frames, aiming to create systems that can bend, flex, and move more like organisms than industrial hardware. That’s all well and good if you’re trying to make machines that can be closely integrated with our bodies, like robotic suits and the like. Dexterity and flexibility, however, often come at the price of strength, given that soft materials are generally less resilient than, say, steel. This latter issue has so far placed a hard-cap on the usefulness of flexible bots (but not on their cuteness.)

Folding for success

Researchers at the Wyss Institute at Harvard University and MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) think they’ve found a way around that cap. The team has created a new kind of artificial muscle that they claim will bring strength to our softbots. In fact, the origami-inspired actuators are so much better than anything we have today, which totally surprised the researchers.

“We were very surprised by how strong the actuators [the artificial muscles] were,” says Daniela Rus, Professor of Electrical Engineering and Computer Science at MIT and one of the senior authors of the paper.

“We expected they’d have a higher maximum functional weight than ordinary soft robots, but we didn’t expect a thousand-fold increase. It’s like giving these robots superpowers,”

Each actuator is based on an inner, skeleton-like structure. This can be constructed out of various material, the team explains, be it plastic sheet or coiled metal. The skeleton is folded in a certain pattern, filled with fluid, and sealed inside a protective ‘skin’ (which can be something be as innocuous as a plastic or textile layer bag).

Proper motion is created through the application of a vacuum inside the bag. As the fluids move out, the skin collapses onto the skeleton and creates tension on the skeleton, causing it to bend. This simplicity is actually a very big plus of the system because it means no other power source or input is required to control how the muscle moves; its motions can be customized while the muscle is being built, simply by altering the shape or composition of the skeleton. The team showed how different skeleton shapes influence motion and overall performance, building devices that can shrink down to 10% of their original size, twist into a coil, or gently lift a flower off the ground.

Artificial muscle fold pattern.

Image credits Li S., Vogt M. et al., 2017, PNAS.

This programmable nature woven into their skeleton is one of the muscles’ “key aspects”, says first author Shuguang Li, a Postdoctoral Fellow at the Wyss Institute and MIT CSAIL. Embedding function in form allows the muscles to be very compact and simple, compared to their counterparts. This making them more appropriate for applications where heavy machinery is a drawback, such as mobile or body-mounted systems.

“You essentially get that motion for free, without the need for a control system,” Li said.

Another advantage is that the muscles, in a limited sense, have built-in intelligence. According to Rus, a muscle that bends in a certain way can potentially help simplify the algorithms needed to run the machine. The muscles, she explains, have a simple on/off switch, so there’s no need to write or run lofty software on how to manage them. This frees up processor and memory space for other uses, without sacrificing mobility.

Like a mallard lifting a car

The muscles are also very strong. They can generate about six times as much force per unit of area than mammalian skeletal muscles (the ones you use to move). A 2.6 gram (0.09 oz) muscle can lift a 3-kilogram (6.61 lb) weight, which the team compares to a mallard lifting a car. Finally, it’s laughably cheap, and the team showed they can build a single muscle in under ten minutes from materials that cost less than a dollar.

Being powered by a vacuum, the origami-like actuators are “safer” than most other types of artificial muscle currently in testing, according to Daniel Vogt, co-author of the paper.

“Vacuum-based muscles have a lower risk of rupture, failure, and damage, and they don’t expand when they’re operating, so you can integrate them into closer-fitting robots on the human body,” he said.

The researchers made artificial muscles made from a wide range of materials, from metal springs or plastic sheets to packing foam. But perhaps most excitingly, they even made some out of PVA, a water-soluble polymer. Such devices could usher in robots that will work in natural settings with almost no environmental impact, as well as swallowable robots that will dissolve after performing their job.

PVA folding actuator.

(B) The actuator can still function when physically constrained, seen here wedged in a bolt nut. (C) Water-soluble polyvinyl alcohol (PVA) actuator being dissolved in hot water (≈ 70 °C) within 5 min.
Image credits Li S., Vogt M. et al., 2017, PNAS.

The researchers also claim the muscles are “highly scalable”, with performance constant across different sizes. The paper’s corresponding author, Rob Wood, says this property lends well to many applications on multiple scales. Surgical and wearable robots, deep-sea robots, all the way to transformable architecture and large deployable structures for space exploration could be based on the actuators, he explains.

“Artificial muscle-like actuators are one of the most important grand challenges in all of engineering,” Wood adds. “Now that we have created actuators with properties similar to natural muscle, we can imagine building almost any robot for almost any task.”

“The actuators developed through this collaboration between the Wood laboratory at Harvard and Rus group at MIT exemplify the Wyss’ approach of taking inspiration from nature without being limited by its conventions, which can result in systems that not only imitate nature, but surpass it,” says the Wyss Institute’s Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and the Vascular Biology Program at Boston Children’s Hospital, as well as Professor of Bioengineering at SEAS.

The paper “Fluid-driven origami-inspired artificial muscles” has been published in the journal PNAS.

The artificial muscle seen here performing biceps motion in order to lift a skeleton's arm to a 90 degree position. Credit: Aslan Miriyev/Columbia Engineering.

Artificial muscle lifts 1,000 times its own weight, brings us closer to humanoid bots

Scientists have come up with an artificial muscle that, in many respects, responds like natural muscle. These artificial muscles could enable humanoid robots to move and act with more grace, possibly mimicking real humans.

The artificial muscle seen here performing biceps motion in order to lift a skeleton's arm to a 90 degree position. Credit: Aslan Miriyev/Columbia Engineering.

The artificial muscle seen here performing biceps motion in order to lift a skeleton’s arm to a 90 degree position. Credit: Aslan Miriyev/Columbia Engineering.

Before robots or androids really permeate society, designers have to make them more human-like. This is not only to make them more familiar or less creepy, but also to improve safety. When working side by side on an assembly line or at home, you really don’t want to injure yourself every time you come across a robot’s metal rods. Ideally, robots that interact often with humans ought to be covered in soft, artificial tissue.

Making more dexterous robots

With this goal in mind, a team led by Aslan Miriyev, a postdoctoral researcher in Columbia University’s Creative Machines Lab, developed a synthetic muscle that pushes, pulls, or twists in response to heat.

Experiments suggest the artificial muscle is capable of lifting 1,000 times its own weight. Even more remarkably, it can expand 15 times more than natural muscle and is also three times stronger.

Beyond robots, the 3-D printed artificial muscle might see a better life augmenting movement for people with disabilities. Since it’s made from biocompatible, relatively inexpensive materials, the artificial muscle could be surgically embedded or used as an exoskeleton prosthesis. No external compressor or high voltage equipment is required, as in previous muscles.

“Our soft functional material may serve as robust soft muscle, possibly revolutionizing the way that soft robotic solutions are engineered today,” said Miriyev. “It can push, pull, bend, twist, and lift weight. It’s the closest artificial material equivalent we have to a natural muscle.

Soft actuator technologies typically use pneumatic or hydraulic inflation to expand elastomer skin with air or liquid. The compressors or pressure-regulating equipment, however, prevents the kind of miniaturization we’d like to see in a humanoid robot that moves gracefully and fluidly like a human would.

To get around bulky actuator equipment, the scientists designed a silicone rubber matrix which expands or contracts as ethanol enters or exits micro-bubbles embedded inside the material. The artificial muscle is actuated with a low-power 8V resistive wire. When heated to 80°C, the artificial muscle could expand to up to 900% its initial size, allowing it to perform motion.

“We’ve been making great strides toward making robots minds, but robot bodies are still primitive,” said Hod Lipson. “This is a big piece of the puzzle and, like biology, the new actuator can be shaped and reshaped a thousand ways. We’ve overcome one of the final barriers to making lifelike robots.”

The team now plans on improving their design. On the drawing board is replacing the embedded wire with conductive materials, accelerating the response time, and increasing the artificial muscle’s shelf life. Ultimately, machine learning algorithms will take control of the muscle’s contractive motion in order to replicate natural movement as closely as possible.

Muscle-like fabric could turn regular clothes into ‘Superman suits’

What a textile exoskeleton might look like. The muscle-like fibers made by Swedish researchers is shown here in black. Credit: Thor Balkhed/Linköping University

These muscle-like textiles made from cellulose yarn can respond to low-voltage electricity to contract just like actual muscle fibers. Clothing made from such a material could help those with disabilities enhance their mobility by providing a far more light-weight alternative to cumbersome exoskeletons. It could also help otherwise healthy people who have physically intensive jobs lessen their load.

“Like a muscle, the actuation is triggered by an electrical potential, driven by a chemical reaction, and operated in an electrolyte,” says study author Edwin Jager, an applied physicist at Linköping University, Sweden.

The fabric was first knitted and woven so it matched the structure of real muscle. It was then bathed in an electroactive solution to make it responsive to electricity. This rather simple recipe allows the fabric to exhibit properties similar to biological muscle, as reported in Science Advances.

The knitted textile offers flexibility while the woven version can exert more force since, like real muscle, woven fibers are coupled in parallel.

“In this case, the extension of the fabric is the same as that of the individual threads. But what happens is that the force developed is much higher when the threads are connected in parallel in the weave,” said Nils-Krister Persson of the Swedish School of Textiles at the University of Borås for ResearchGate.

The strong and flexible textile could be sewn into parts of clothing, like the sleeve tights, to made movement easier, i.e. use less energy. Right now, some people with motor disabilities use exoskeletons powered by motors or pressurized air to move about but these can cost $50,000 onward.

“Enormous and impressive advances have been made in the development of exoskeletons, which now enable people with disabilities to walk again. But the existing technology looks like rigid robotic suits. It is our dream to create exoskeletons that are similar to items of clothing, such as “running tights” that you can wear under your normal clothes. Such device could make it easier for older persons and those with impaired mobility to walk,” Jager said in a statement for the press.

That’s not to say that the muscle-like fiber made by the Swedish researchers can come close to exoskeleton practicality. The fiber was used to move a LEGO lever and lift a two-gram weight when an electrical current was passed through it but you’d need to do far more than that for it to be functional. There are also a couple of other limitations that right now make the fiber rather impractical, like the fact that it requires an electrolyte to actuate the artificial muscles. The researchers hope to make it work using only air instead.

Even so, this is some exciting research and might one day develop into a much more promising technology.

“I hope that this work will inspire others to look into the possibilities of textile technology,” says Jager. “My collaborators have taught me that textiles, ubiquitous as they are, can truly be high-tech technology.”

When cut in half, the elastomer can join back if the edges are placed closed enough. Credit: Cheng-Hui Li, Stanford University

Self-healing artificial muscle made at Stanford University

There’s nothing like biological muscles, but the synthetic variety is getting mighty close. Scientists made artificial muscles from all sorts of materials, from nanotech yarn that’s 85 times more powerful than natural muscles, to onions that can be bent and stretched much like a muscle. The closest we’ve come to natural muscles is a novel elastomer developed at Stanford University, Palo Alto that can stretch 45 times its length and return to its original size. It’s also self-healing.

When cut in half, the elastomer can join back if the edges are placed closed enough. Credit: Cheng-Hui Li, Stanford University

When cut in half, the elastomer can join back if the edges are placed close enough. Credit: Cheng-Hui Li, Stanford University

Materials chemist Zhenan Bao and colleagues found the right balance of stretching and strength in Fe-Hpdca-PDMS — a rubber-like material comprised of entangled polymer chains made of silicon, oxygen, nitrogen and carbon atoms, all sprinkled with some iron salt.

The iron is essential to the elastomer’s integrity as it bonds to the oxygen and nitrogen, joining polymer chains in the process like tied shoe laces. The polymer chains are thus linked both to themselves and each other allowing the chains to move, and the material as a whole to stretch.

After the material is stretched, the crosslinks return to their original size.

The most remarkable ability of Stanford’s artificial muscle though is by far the self-healing capability. If you poke a hole in the material, the material will cover it up. That’s because the iron atoms on one side of the hole are attracted to the oxygen and nitrogen atoms on the other. In only 72 hours, a micro-hole is self-healed. Even when the researchers cut the material in half, the cut edges joined back together if these were placed close enough, still retaining 90 percent of its stretchability.

It’s not perfect, though. For artificial muscles to be used in a prosthetic or in the soft limb of a robot, these need to be responsive to electric fields. Stanford’s artificial muscle changes in length by only 2% when an electric field is applied, versus 40 percent in the case of biological muscle.

“In our case, the goal was not to make the best artificial muscle, but rather to develop new materials design rules for stretchable and self-healing materials,” Bao explains. “Artificial muscle is one potential application for our materials.”

Combined with artificial skin that can ‘feel’ or even sprout hair and sweat, Bao’s elastomer could form a very interesting artificial system that mimics the real deal. The remarkable self-healing potential makes it an interesting solution for sensors that need to be placed in extreme conditions where damage is common.

Findings appeared in the journal Nature Chemistry.


onion muscle

Scientists make muscles out of gold plated onions

When it comes to artificial muscles, researchers at from National Taiwan University really know their onions. The team applied an uncanny design in which they layered gold atop the treated skin of onions. Once an electrical current was discharged, the “onion muscle” contracted and bent, just like the real thing. There’s a whole slew of possible applications for artificial muscles, from so-called “soft robotics” (flesh-like droids), to of course helping injured humans.

onion muscle

Image: Flickr // Onion Fights

Most artificial muscle models presented thus far were made from polymers, and unfortunately fail when it comes to replicating real muscle quality like staying soft and bendable even when contracting.

“There are artificial muscles developed using elastomers, shape memory alloys, piezoelectric composites, ion-conductive polymers and carbon nanotubes,” says Wen-Pin Shih of National Taiwan University in Taipei for ZME Science. “The driving mechanisms and functions are very diverse.”

Onion is not only a cheaper natural substitute to polymers, it’s actually far better for the task at hand. The team only used the epidermis of the onion, however – its skin. This thin film is both stretchy and responsive to electricity. The skin was then freeze-dried to remove any excess water, then bathed in dilute sulfuric acid to increase elasticity by removing the hemicellulose, a protein that makes the cell walls rigid. Gold was layered on both sides for increased electrical conductivity. Finally, when a current was transferred through the onion, it bent and stretched much like a muscle. What a tear jerker!

“We intentionally made the top and bottom electrodes a different thickness so that the cell stiffness becomes asymmetric from top to bottom,” said Shih.

Indeed, this way when a low voltage (0 to 50 volts) was applied the onion muscle expanded and flexed downwards, while a high voltage (50 to 1000 volts) caused the cells to contract and flex upwards. By carefully controlling the voltage, the team was able to grab a small cotton ball using the onion muscle.

Schematic details the process of transforming onion skin cells into muscles. Image: Shih Lab, National Taiwan University.

Schematic details the process of transforming onion skin cells into muscles. Image: Shih Lab, National Taiwan University.

The high voltage, however, makes it impracticable for use in mobile applications like tiny bots, which typically use small batteries. “We will have to understand the configuration and mechanical properties of the cell walls better to overcome this challenge,” Shih notes.

Also, another drawback of using vegetables in high tech devices is durability. Decay and water infiltration are two main issues that need to be highlighted, with this in mind. Shih already has a plan for this: applying a very thin fluoride layer to keep water out, while also retaining the bending/contracting ability. The onion muscles was reported in a paper published in  Applied Physics Letters.

Artificial muscle is quite the thing in research today. A while ago, ZME Science reported how University of Texas at Dallas researchers found a way to manufacture artificial muscle that is up to 100 times stronger than the flimsy tissue that makes up the human biceps. The material is made out of nylon fibers – the stuff fishnets are made of – that are tensed almost to the upper limit and thermal processed to retain a high energy density.

Photograph comparing muscles made by coiling (from left to right) 150 μm, 280 μm, 860 μm and 2.45 mm nylon 6 monofilament fibers. Photo: Science

Synthetic muscle made from nylon is 100 times stronger than human muscle

Sometimes, I come across stories or various research that make me wonder “why the heck hasn’t anyone else thought of this before?” We should be grateful, nevertheless, that researchers from University of Texas at Dallas have found a way to manufacture artificial muscle that is up to 100 times stronger than the flimsy tissue that makes up the human biceps. The material is made out of nylon fibers – the stuff fishnets are made of – that are tensed almost to the upper limit and thermal processed to retain a high energy density.

Like very thin springs, the synthetic muscle is cheap, easy to make and durable. Of course it has some drawbacks, however the researchers envision its introduction in the industry extremely fast considering the facts. Applications include artificial muscles for robots, exoskeleton suits, or automatically heat-regulated window shutters and ventilation systems.

Photograph comparing muscles made by coiling (from left to right) 150 μm, 280 μm, 860 μm and 2.45 mm nylon 6 monofilament fibers. Photo: Science

Photograph comparing muscles made by coiling (from left to right) 150 μm, 280 μm, 860 μm and 2.45 mm nylon 6 monofilament fibers. Photo: Science

The process through which the synthetic sinew is coiled is quite trivially simple. Basically, it boils down to making sure you apply the right tension and weight to the thread when twisting it. Actually, according to the scientists involved in the work, similar nylon coils like the ones they produced can be made by regular people at home.

Nylon or polyethylene gets twisted under high tension over and over again until it reaches a certain strain threshold. Once the plastic can’t twist any more, it starts to coil up on itself like a curled telephone cord. The coil is then thermally treated so it gets locked in place; along with energy stored in the coil. When the resulting coil is heated, it begins to untwist, but in the process the whole whole material begins to compress.

“At first it seems confusing, but you can think of it kind of like a Chinese finger-trap,” says Ray Baughman, a materials scientist with the team. “Expanding the volume of the finger-trap, or heating the coil, actually makes the device shorten.”

By braiding and twisting different threads together and coiling them in different ways, you can end up with different kinds of variations in muscle strength, depending on the kind of application you’re looking for. Also, by blending in conductive wire or wrapping the muscle with a light-absorbing coating, the researchers can control the muscles’ movements with electricity and light instead of direct heat.

Photo: University of Texas at Dallas.

Photo: University of Texas at Dallas.

At the moment, the nylon artificial muscle isn’t all that efficient. While work is presently underway to solve inefficiency issues, by itself, even in its current form, this research is extremely impressive and will most likely get used in real-world applications real soon. It also is a great example of what you can achieve with readily available materials and technology just by applying novel tricks and strategies.

You can find out more in the paper published just today in the journal Science.

Nanootech yarn muscle

Super-strong artificial muscles made from nanotech yarn

Scientists at University of Texas Dallas have made artificial muscles capable of supporting 100,000 times their own weight and generate 85 times more mechanical power than natural muscle of the same size. Applications for this kind of technology are quite numerous, ranging from extremely strong and intelligent textiles to high-temperature applications since the fabric has a negative thermal expansion coefficient.

Nanootech yarn muscle

The diameter of this coiled yarn is about twice the width of a human hair. (c) UT Dallas

The artificial muscles were constructed from carbon nanotubes, tiny hallow cylinders made from the same made from the same type of graphite layers found in the core of ordinary pencils. The nanotubes were put together as to constitute a string of yarn. The yarn was infiltrated with simple paraffin wax, commonly found in candles, and then twisted. Because the wax is a “volume changer”, when the composite twisted yarn was heated either electrically or using a flash of light the wax expanded. As such the yarn volume increased, and the yarn length contracted.

“The artificial muscles that we’ve developed can provide large, ultrafast contractions to lift weights that are 200 times heavier than possible for a natural muscle of the same size,” said Dr. Ray Baughman, team leader, Robert A. Welch Professor of Chemistry and director of the Alan G. MacDiarmid NanoTech Institute at UT Dallas. “While we are excited about near-term applications possibilities, these artificial muscles are presently unsuitable for directly replacing muscles in the human body.”

Smart fabric made out of nanotech yarn

Muscle contraction – also called actuation – can be ultrafast, occurring in 25-thousandths of a second. Including times for both actuation and reversal of actuation, the researchers demonstrated a contractile power density of 4.2 kW/kg, which is four times the power-to-weight ratio of common internal combustion engines.

“Because of their simplicity and high performance, these yarn muscles could be used for such diverse applications as robots, catheters for minimally invasive surgery, micromotors, mixers for microfluidic circuits, tuneable optical systems, microvalves, positioners and even toys,” said Baughman.

For instance, because of their ultra-fast expansion/contraction to slight temperature changes, the artificial muscles could be employed in smart clothing whose textile porosity could change in order to provide thermal or chemical comfort. The yarn can be easily twisted together, woven, sewn, braided and knotted.

Also the yarn has been found to contract only by 7% when lifting heavy loads at a whooping 2,500 degrees Celsius – that’s 1000 degrees past the melting point of steel, where no other high-work-capacity actuator has been able to survive.

“The remarkable performance of our yarn muscle and our present ability to fabricate kilometer-length yarns suggest the feasibility of early commercialization as small actuators comprising centimeter-scale yarn length,” Baughman said. “The more difficult challenge is in upscaling our single-yarn actuators to large actuators in which hundreds or thousands of individual yarn muscles operate in parallel.”

The findings were reported in the journal Science,


Scientists create artificial muscles from nanotubes

Scientists have made another step closer to the bionic man, after creating nanotubes out of carbon straws that can contract in a similar fashion to real muscles.

The team from the University of British Columbia have created the strong and flexible artificial muscles that could also be used to propel nanobots through the body to diagnose and treat a conditions. The nanotubes are capable of spinning 600 revolutions per minute, and turning a weight that is 2,000 times heavier than itself – they are also 100 times stronger than steel.

“What’s amazing is that these barely visible yarns [the name of the structure] composed of fibres 10,000 times thinner than a human hair can move and rapidly rotate objects two thousand times their own weight,” said John Madden from the department of electrical and computer engineering in a press release.

The nanotubes are made from carbon atoms linked together in hexagons and lined up like a tube; these tubes are then fondled together to form the yarn structure, which brings it its amazing properties.

“While not large enough to drive an arm or power a car, this new generation of artificial muscles — which are simple and inexpensive to make — could be used to make tiny valves, positioners, pumps, stirrers and flagella for use in drug discovery, precision assembly and perhaps even to propel tiny objects inside the bloodstream.”

The muscle was developed in collaboration with the University of Wollongong in Australia, the University of Texas at Dallas and Hanyang University in Korea.

Via Toronto Sun