“Electrically-Charged Hydrogel has applications for soft robotics and biomedical fields”

Article Summary - By Randall Marsh
Soft robotics is a quickly emerging field that takes a lot of inspiration from marine creatures like squids and starfish. A light-controlled hydrogel was recently developed that could be used for control of these new robotic devices, but now researchers at North Carolina State University are taking the development of soft robotic devices to a new level with electrically-charged hydrogels.

What is IONOPRINTING ?

Researchers at NC State have developed a method called ‘ionoprinting’ with the capability to pattern and actuate hydrated gels in two and three dimensions by locally patterning ions using electric fields. The ability to pattern, structure, re-shape and actuate hydrogels is important for biomimetics, soft robotics, cell scaffolding and biomaterials.

The ionic binding changes the local mechanical properties of the gel to induce relief patterns and in some cases evokes localized stresses large enough to cause rapid folding. These ionoprinted patterns are stable for months, yet the ionoprinting process is fully reversible by immersing the gel in a chelator. The mechanically patterned hydrogels exhibit programmable temporal and spatial shape transitions and serve as a basis of a new class of soft actuators able to gently manipulate objects both in air and in liquid.

The paper, “Reversible patterning and actuation of hydrogels by electrically assisted ionoprinting” is co-authored by Etienne Palleau, Daniel Morales, Michael Dickey and Orlin Velev and published in Nature Communications. The work was supported by the National Science Foundation Triangle MRSEC program and the French DGA.

Resource Links:

http://ionoprinting.com/

http://www.nature.com/ncomms/2013/130802/ncomms3257/fig_tab/ncomms3257_F1.html

http://www.gizmag.com/electrically-charged-hydrogel-soft-robotics/28576/

Video – http://youtu.be/9SXWJP1KK-8

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Now researchers at MIT, Harvard University and Seoul National University have engineered a soft autonomous robot that moves via peristalsis, crawling across surfaces by contracting segments of its body, much like an earthworm. The robot, made almost entirely of soft materials, is remarkably resilient: Even when stepped upon or bludgeoned with a hammer, the robot is able to inch away, unscathed.

Sangbae Kim, the Esther and Harold E. Edgerton Assistant Professor of Mechanical Engineering at MIT, says such a soft robot may be useful for navigating rough terrain or squeezing through tight spaces.

The robot is named “Meshworm” for the flexible, meshlike tube that makes up its body. Researchers created “artificial muscle” from wire made of nickel and titanium — a shape-memory alloy that stretches and contracts with heat. They wound the wire around the tube, creating segments along its length, much like the segments of an earthworm. They then applied a small current to the segments of wire, squeezing the mesh tube and propelling the robot forward. The team recently published details of the design in the journal IEEE/ASME Transactions on Mechatronics.

In addition to Kim, the paper’s authors are graduate student Sangok Seok and postdoc Cagdas Denizel Onal at MIT, associate professor Robert J. Wood at Harvard, assistant professor Kyu-Jin Cho PhD ’07 of Seoul National University, and Daniela Rus, professor of computer science and engineering and director of MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL).

Soft-Serve Robotics

In the past few decades, many roboticists have looked for ways to engineer soft robotic systems. Without bulky, breakable hardware, soft robots might be able to explore hard-to-reach spaces and traverse bumpy terrain. Their pliable exteriors also make them safe for human interaction.

A significant challenge in soft robotics has been in designing soft actuators, or motors, to power such robots. One solution has been to use compressed air, carefully pumped through a robot to move it. But Kim says air-powered, or pneumatic, robots require bulky pumps. “Integrating micro air compressors into a small autonomous robot is a challenge,” Kim says.

Artificial Muscle from a Bizarre Material – (Nickel Titanium)

Instead, Kim and his colleagues looked to the earthworm for design guidance. They noted that the creepy crawler is made up of two main muscle groups: circular muscle fibers that wrap around the worm’s tubelike body, and longitudinal muscle fibers that run along its length. Both muscle groups work together to inch the worm along.

The team set out to design a similar soft, peristalsis-driven system. The researchers first made a long, tubular body by rolling up and heat-sealing a sheet of polymer mesh. The mesh, made from interlacing polymer fibers, allows the tube to stretch and contract, similar to a spring.

They then looked for ways to create artificial muscle, ultimately settling on a nickel-titanium alloy. “It’s a very bizarre material,” Kim says. “Depending on the [nickel-titanium] ratio, its behavior changes dramatically.”

Depending on the ratio of nickel to titanium, the alloy changes phase with heat. Above a certain temperature, the alloy remains in a phase called austenite — a regularly aligned structure that springs back to its original shape, even after significant bending, much like flexible eyeglass frames. Below a certain temperature, the alloy shifts to a martensite phase — a more pliable structure that, like a paperclip, stays in the shape in which it’s bent.

The researchers fabricated a tightly coiled nickel-titanium wire and wound it around the mesh tube, mimicking the circular muscle fibers of the earthworm. They then fitted a small battery and circuit board within the tube, generating a current to heat the wire at certain segments along the body: As a segment reaches a certain temperature, the wire contracts around the body, squeezing the tube and propelling the robot forward. Kim and his colleagues developed algorithms to carefully control the wire’s heating and cooling, directing the worm to move in various patterns.

The group also outfitted the robot with wires running along its length, similar to an earthworm’s longitudinal muscle fibers. When heated, an individual wire will contract, pulling the worm left or right.

As an ultimate test of soft robotics, the group subjected the robot to multiple blows with a hammer, even stepping on the robot to check its durability. Despite the violent impacts, the robot survived, crawling away intact.

“You can throw it, and it won’t collapse,” Kim says. “Most mechanical parts are rigid and fragile at small scale, but the parts in Meshworms are all fibrous and flexible. The muscles are soft, and the body is soft … we’re starting to show some body-morphing capability.”

Kellar Autumn, a professor of biology at Lewis and Clark College, studies the biomechanics of animal motion in designing soft robotics. Autumn says robots like the Meshworm may have many useful applications, such as next-generation endoscopes, implants and prosthetics.

“Even though the robot’s body is much simpler than a real worm — it has only a few segments — it appears to have quite impressive performance,” Autumn says. “I predict that in the next decade we will see shape-changing artificial muscles in many products, such as mobile phones, portable computers and automobiles.”

This research was supported by the U.S. Defense Advanced Research Projects Agency.

Links

http://web.mit.edu/newsoffice/2012/autonomous-earthworm-robot-0810.html
Youtube Video – http://youtu.be/EXkf62qGFII

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Having already broken new ground in robotics with the development, last year, of a class of “soft”, silicone-based robots based on creatures like squid and octopi, Harvard scientists are now working to create systems that would allow the robots to camouflage themselves, or stand out in their environment.

As described in a paper published August 16 in Science, a team of researchers led by George M. Whitesides, the Woodford L. and Ann A. Flowers University Professor, has developed a “dynamic coloration” system for soft robots that might one day have applications ranging from helping doctors plan complex surgeries to acting as a visual marker to help search crews following a disaster.

In this video, Stephen Morin, a Post-Doctoral Fellow in Chemistry and Chemical Biology and first author of the paper, discusses the research and demonstrates how the system works.

Links

http://www.youtube.com/watch?v=bC1WFU4G-WU

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There’s just something about those  air muscles that soft robots use that creeps me out, but it’s hard to deny that as the designs get more and more refined, the robots themselves are getting capable enough to actually, you know, start doing stuff. Take this soft robot from Harvard, for example: it not only walks, it knows several different gaits and can deflate to stuff itself through tiny little gaps.

And there’s nothing solid in there at all: You could probably smash this thing with a hammer a whole bunch of times and it would still keep coming for you. And that’s part of the idea. The other part of the idea is that soft robots can adapt themselves to squeeze through gaps (as in the vid above) and otherwise get into places that robots with rigid structures might not be able to.

This particular robot (which comes from George M. Whitesides‘ lab at Harvard) distinguishes itself by being capable of several unique gait styles including walking, crawling, and slithering. Each of these gaits is controlled by pumping air at up to 10 psi into a succession of limbs, inflating and deflating elastomer compartments to provide temporary structure and rigidity. In addition to slipping through gaps, the robot can make it across things like felt cloth, gravel, mud, and Jell-O (don’t ask).

As the Harvard researchers explain in a paper in PNAS, the robot was inspired by animals like squid, starfish, worms that “do not have hard internal skeletons,” and the advantage of soft robotics is that “simple types of actuation produce complex motion.”

Pretend to act shocked that the development of this robot has been funded by DARPA, and then start exercising your imagination as to what could be done with an indestructible, unstoppable, squishably soft little robot.

http://youtu.be/2DsbS9cMOAE

“They need to make one that doesn’t have all those wires sticking out of its ass!”
(Youtube User Comment )

Camouflage Bendy Robot Changes Colour for Disguise

By Rebecca MorelleScience reporter, BBC News

A robot that can change colour to either blend in with or stand out from its surroundings has been created by scientists. The machine, designed by researchers at Harvard University, was inspired by the camouflage skills of sea creatures such as octopuses, cuttlefish and squid.

Like these cephalopods, the robot has a soft, rubbery body and can move with flexibility. The study is published in the journal Science. Professor George Whitesides, an author of the paper, said: “Conventional robotics is a pretty highly developed area, and if you look at various robots you find that most are basically built on the body plan of a mammal. “Our question is: Why do you have to do that? Why not think about organisms that are soft, that might have quite different structures and ways of moving and strategies for camouflage. And the obvious place to look is underwater.”

In 2011, the research team published a paper in the Proceedings of the National Academy of Sciences (PNAS) that outlined details of a “soft robot” that could crawl and bend under obstacles. The machine was made from silicon-based polymers, and its movement was driven by air pumping through tiny cylinders in its four “legs”.

Now the scientists have added another layer of complexity to these robots by giving them the ability to disguise themselves. The camouflage-bots are covered in a network of tiny channels. As different dyes are pumped in, the robots can quickly change their appearance. As well as changing colour, hot or cold fluids can be pumped into robots, enabling them to be thermally camouflaged, and fluorescent liquids allow them to glow in the dark.

Currently, the fluid is pulled in from a reservoir, but in the future it could be incorporated into the robot’s body.

Search and Rescue

Lead author Stephen Morin said the soft machines had similarities with organs or tissues and could have medical applications. He explained: “The idea is that if you have a system that can simulate muscle motion very well and a system that can transport fluid, by combining those you can fabricate that device to fit a specific surgical problem. “And in planning for surgery or training, you can use something like this in guilt-free way.”

The team also said the machines could have a future in search and rescue.  Prof Whitesides said: “For that kind of application, having it be able to advertise itself, for example, in a way that stood out against the dark would be a good thing.” He said the fact that the robots were lightweight, flexible and also relatively inexpensive was advantageous. He explained: “The nice thing about these systems is that their properties are very different from conventional robots. You get pretty complicated motions from pretty simple systems.

“For a mission like search and rescue, these kind of robots could in principle be throwaway. So if you took a $25,000 robot and sent it in and the building falls down, then that is a real issue. If you send one in which is $100 and the roof falls in, you really don’t care.”

http://www.bbc.co.uk/news/science-environment-19286259

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