#soft robots

Taking WIng

Dramatic events in biology often inspire designs that mimic life. Here young fruit flies (Drosophila melanogaster) deploy their wings for the first time in a cross between an explosion and careful origami-like unfolding – a little like pop-up tents (although 1000 times smaller). The unfurling is propelled by a release of pressure and rush of fly blood called haemolymph into the new wings. Biotechnologists study the explosive release in both female (top row) and male (bottom) flies, using several imaging techniques while exploring the wings’ kinematics – their moving geometry – using computational modelling. These studies may shed some light on how tissues emerge on different time scales: in flies and genetically similar organisms, like humans. The miniature mechanics involved may also influence the design of soft robots able to quickly remodel themselves, perhaps during intricate medical procedures.

Written by John Ankers

Video from work by Simon Hadjaje and colleagues

Aix-Marseille University, CNRS, IBDM & Turing Centre for Living Systems (CENTURI), Marseille, France

Video contributed by the authors under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence

Published in Nature Communications, December 2024

“A “soft robot” can move its way through the human body solely by the changing of temperatures, and could be an excellent way to deliver precision doses of key medications.

These “gelbots” aren’t really robots at all, but little capsules filled with a water-based gel that through expansion and contraction, pushes the tiny robot along like an inchworm.

Robots are made almost exclusively of hard materials like metals and plastics, a fundamental obstacle in the push to create robots ideal for human biomedical advancements.

Water-based gels, which feel like gummy bears, are one of the most promising materials in the field of soft robotics. Researchers have previously demonstrated that gels which swell or shrink in response to temperature can be used to create smart structures.

Here, the Johns Hopkins University team demonstrated for the first time, how swelling and shrinking of gels can be strategically manipulated to move robots forward and backward on flat surfaces, or to essentially have them crawl in certain directions with an undulating, wave-like motion.

“It seems very simplistic but this is an object moving without batteries, without wiring, without an external power supply of any kind—just on the swelling and shrinking of gel,” said senior author David Gracias, a professor of chemical and biomolecular engineering at Johns Hopkins University...

As well as potentially delivering targeted medications inside the human body, the development team considers them ideal for oceanfloor monitoring.

Made of little more than simple stuff, the team 3D-printed all their gelbots, and posit that as another advantage of soft robotics over hard robotics.

Gracias hopes to train the gelbots to crawl in response to variations in human biomarkers and biochemicals, although skin surface temperature manipulation with hot and cold objects could also work to inch it along.

A new type of soft robot gets its power from the skin it’s in.

This robotic skin bends, stretches and contracts. That flexibility lets it wrap around inanimate objects. Wrap it around the legs of a stuffed animal and presto! A flexible lightweight robot. Putting removable, reusable sheets of this “skin” on other objects could turn them into useful grippers or wearable devices. Researchers described their new invention online September 19, 2018 in Science Robotics.

“It’s an interesting approach,” says Christopher Atkeson. He’s a roboticist at Carnegie Mellon University in Pittsburgh, Pa., who did not work on the project. Sometimes it might be simpler to use a soft ready-made robot for a specific purpose. Like squeezing through tight spaces, for example, or gently grabbing objects. The new robotic skins might come in handy for other things, such as search-and-rescue operations or space exploration. These are missions where users might not know in advance what types of robotic helpers they’ll need. They also are missions where packing light is key, Atkeson notes.

Explainer: What are polymers?

Each piece of robotic skin is made of an elastic polymer (PAHL-ih-murr) or fabric. That stretchy skin can hold air pouches that inflate when pumped full of gas. Or it might hold nickel titanium (Ty-TAY-nee-um) coils that contract when heated by an electric current. Such gas pouches or coils would allow the robotic skin to move and change shape.

Rebecca Kramer-Bottiglio is an engineer at Yale University in New Haven, Conn. She and colleagues used the skin to build several robots. They gave the robots different types of motion two ways. In one, they changed the layout of air pouches or coils in the skin. For the other, they attached pieces of skin to an object in various ways.

Scientists Say: Engineering

For instance, wrapping the skin around foam tubes in one direction created robots that crawled like inchworms. Wrapping it another direction created robots that paddled forward on two ends. Patches of robotic skin around three foam fingers created a soft robot “grabber.”

The researchers also fastened robotic skin to a shirt to create a garment that monitors posture. Whenever the skin sensed the user’s shoulders slumping, it wriggled gently as a reminder to sit up straight. Robotic skin stitched into clothing could give the wearer a massage. Or it could provide tactile (touch) feedback in virtual reality systems, Atkeson says.

The robotic skin isn’t ready for off-the-shelf use just yet. To work, each piece must be tethered to hoses or wires. These feed into its gas pouches or electric coils. But future versions might include portable air pressure and electricity devices, Kramer-Bottiglio says.

Bust a Move

Entering stage-left like a disco dancer with a score to settle, this tiny ‘soft robot’ makes a determined effort to cross the floor. All the more impressive as people keep sticking knives into its limbs. This quadruped robot is made from a self-healing material – an elastomer that repairs after the cuts, combined with wavy light sensors capable of detecting stress and damage then feeding the information back to a controlling computer. In this particular model, after every cut the robot adjusts its movement – it’s gait – to compensate for its injuries. Researchers believe this new generation of flexible electronics gains a form of awareness or 'damage intelligence' – they’re not only resilient to damage but can adapt to it. Similar robots may be suited to working inside or alongside the body, monitoring stresses and strains on and off the dance floor.

Written by John Ankers

Video by Hedan Bai, Young Seong Kim & Robert F. Shepherd (edited)

Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Science Advances, December 2022

Apeeling Design

Channels, tunnels and tubes – life relies on vessels to move fluids around, with our circulatory system transporting cells, chemicals and warmth all over the body. Biomedical engineers often mimic this pipework to learn about the physics involved, but also to watch commuting cells adapting to travel inside. Here researchers overcome a hurdle to more ambitious 3D designs for their networks of microchannels. First, they allow a plastic material to set around wire-like templates of soft resin. Once set, they pull out the templates which become thinner as they stretch, peeling away from the inside of each tube gently, where a solid wire might split or crack the design. They are left with these networks of channels – examples of how this 'soft demoulding' process could be adapted for microfluidic devices, or even used in the pneumatic systems of soft robots designed to help around the body.

Written by John Ankers

Image from work by Dongliang Fan and colleagues

Shenzhen Key Laboratory of Biomimetic Robotics and Intelligent Systems, Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, August 2022

Do the Locomotion

For some creatures, speed is everything. Catching prey or avoiding being prey fuels an evolutionary race in nature’s greatest runners – and mimicking their sprints might be a weapon against disease. These tiny running soft robots are made from 3D printed elastic polymer embedded with metal wires. They bend and stretch due to electromotive forces caused by changes in current piped in from outside – giving this jolly arch a gait similar to a cheetah (arguably its locomotion is even faster when measured in body lengths per second). Robots can be fitted with different feet for different surfaces (later in the video) or even swim. These examples are tethered to an eternal power supply, but work is underway on a free-roaming version, currently about as fast as a centipede. Researchers hope similar robots can help to deliver drugs inside humans, possibly dashing towards a finish line somewhere in our intestines.

Written by John Ankers

Video from work by Guoyong Mao and David Schiller, and colleagues

Soft Materials Lab, Linz Institute of Technology, Johannes Kepler University, Linz, Austria

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, August 2022