Morphing robot turns challenging terrain to its advantage

A bioinspired robot developed at EPFL can change shape to alter its own physical properties in response to its environment, resulting in a robust and efficient autonomous vehicle as well as a fresh approach to robotic locomotion.

Ecole Polytechnique Fédérale de Lausanne

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The morphing Good Over All Terrains (GOAT) robot in sphere mode © CREATE EPFL

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Credit: © CREATE EPFL

From mountain goats that run up near-vertical rock faces to armadillos that roll into a protective ball, animals have evolved to adapt effortlessly to changes in their environment. In contrast, when an autonomous robot is programmed to reach a goal, each variation in its pre-determined path presents a significant physical and computational challenge.

Researchers led by Josie Hughes in the CREATE Lab in EPFL’s School of Engineering wanted to develop a robot that could traverse diverse environments as adeptly as animals by changing form on the fly. With GOAT (Good Over All Terrains) they have achieved just that – and created a new paradigm for robotic locomotion and control in the process.

Thanks to its flexible yet durable design, GOAT can spontaneously morph between a flat ‘rover’ shape and a sphere as it moves. This allows it to switch between driving, rolling, and even swimming, all while consuming less energy than a robot with limbs or appendages.

“While most robots compute the shortest path from A to B, GOAT considers the travel modality as well as the path to be taken,” Hughes explains. “For example, instead of going around an obstacle like a stream, GOAT can swim straight through. If its path is hilly, it can passively roll downhill as a sphere to save both time and energy, and then actively drive as a rover when rolling is no longer beneficial.”

The research has been published in Science Robotics.

Compliance is key

To design their robot, the CREATE team took inspiration from across the animal kingdom, including spiders, kangaroos, cockroaches, and octopuses.The team’s bioinspired approach led to a design that is highly compliant, meaning it adapts in response to interaction with its environment, rather than remaining rigid. This compliance means that GOAT can actively alter its shape to change its passive properties, which range from more flexible in its ‘rover’ configuration, to more robust as a sphere.

Built from inexpensive materials, the robot’s simple frame is made of two intersecting elastic fiberglass rods, with four motorized rimless wheels. Two winch-driven cables change the frame’s configuration, ultimately shortening like tendons to draw it tightly into a ball. The battery, onboard computer, and sensors are contained in a payload weighing up to 2 kg that is suspended in the center of the frame, where it is well protected in sphere mode – much as a hedgehog protects its underbelly.

The path of least resistance

CREATE Lab PhD student Max Polzin explains that compliance also allows GOAT to navigate with minimal sensing equipment. With only a satellite navigation system and a device for measuring the robot’s own orientation (inertial measurement unit), GOAT carries no cameras onboard: it simply does not need to know exactly what lies in its path.

“Most robots that navigate extreme terrain have lots of sensors to determine the state of each motor, but thanks to its ability to leverage its own compliance, GOAT doesn’t need complex sensing. It can leverage the environment, even with very limited knowledge of it, to find the best path: the path of least resistance,” Polzin says.

Future research avenues include improved algorithms to help exploit the unique capabilities of morphing, compliant robots, as well as scaling GOAT’s design up and down to accommodate different payloads. Looking ahead, the researchers see many potential applications for their device, from environmental monitoring to disaster response, and even extraterrestrial exploration.

“Robots like GOAT could be deployed quickly into uncharted terrain with minimal perception and planning systems, allowing them to turn environmental challenges into computational assets,” Hughes says. “By harnessing a combination of active reconfiguration and passive adaptation, the next generation of compliant robots might even surpass nature’s versatility.”

The morphing Good Over All Terrains (GOAT) robot in rover mode © CREATE EPFL

 

The morphing Good Over All Terrains (GOAT) robot in sphere mode © CREATE EPF

Journal

Science Robotics

DOI

10.1126/scirobotics.adp6419 

Method of Research

Experimental study

Article Title

Robotic Locomotion through Active and Passive Morphological Adaptation in Extreme Outdoor Environments

Article Publication Date

26-Feb-2025

A springtail-like jumping robot

Diminutive device can leap 23 times its body length

Harvard John A. Paulson School of Engineering and Applied Sciences

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The Harvard Ambulatory Microrobot modified with its springtail-inspired jumping mechanism.

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Credit: Harvard Microrobotics Laboratory

Springtails, small bugs often found crawling through leaf litter and garden soil, are expert jumpers. Inspired by these hopping hexapods, roboticists in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have made a walking, jumping robot that pushes the boundaries of what small robots can do.

Published in Science Robotics, the research glimpses a future where nimble microrobots can crawl through tiny spaces, skitter across dangerous ground, and sense their environments without human intervention. 

The new Harvard robot was created in the lab of Robert J. Wood, the Harry Lewis and Marlyn McGrath Professor of Engineering and Applied Sciences at SEAS. It is a modification of the Harvard Ambulatory Microrobot (HAMR), a microrobotic platform originally modeled after the dexterous, hard-to-kill cockroach. Now, HAMR is outfitted with a robotic furcula – the forked, tail-like appendage tucked under a springtail’s body that it pushes off the ground to send it Simone Biles-ing into the air.

“Springtails are interesting as inspiration, given their ubiquity, both spatially and temporally across evolutionary scales,” Wood said. “They have this unique mechanism that involves rapid contact with the ground, like a quick punch, to transfer momentum and initiate the jump.”

To go airborne, the robot uses what’s called latch-mediated spring actuation, in which potential energy is stored in an elastic element – the furcula – that can be deployed in milliseconds like a catapult. This physical phenomenon is found time and again in nature, not just in springtails: from the flicking tongue of a chameleon to the prey-killing appendage of a mantis shrimp. 

Wood’s team previously created a mantis shrimp-inspired punching robot. “It seemed natural to try to explore the use of a similar mechanism, along with insights from springtail jumps, for small jumping robots,” Wood said. 

The springtail’s furcula is also elegantly simple, composed of just two or three linked units. “I think that simplicity is what initially charmed me into exploring this type of solution,” said first author and former SEAS research fellow Francisco Ramirez Serrano.

The team used streamlined microfabrication workflows pioneered in the Wood lab to develop the palm-sized, paper clip-light robot that can walk, jump, climb, strike, and even scoop up objects.

The robot demonstrates some of the longest and highest jumps of any existing robot relative to body length; its best performance is 1.4 meters, or 23 times its length. By contrast, a similar robot can jump twice as far but outweighs the Harvard robot by 20 times.

“Existing microrobots that move on flat terrain and jump do not possess nearly the agility that our platform does,” Serrano said.

The team incorporated detailed computer simulations into the design of the robot to help it land optimally every time, precisely controlling for the lengths of its linkages, the amount of energy stored in them, and the orientation of the robot before takeoff.

Packing all manner of athletic abilities into one lightweight robot has the team excited for a future where robots like theirs could traverse places humans can’t or shouldn’t. 

“Walking provides a precise and efficient locomotion mode but is limited in terms of obstacle traversal,” Wood said. “Jumping can get over obstacles but is less controlled. The combination of the two modes can be effective for navigating natural and unstructured environments.”

The research was supported by the U.S. Army Research Office under grant No. W911NF1510358.

Jumping video [VIDEO] | 

Still image of the springtail-inspired robot. 

Credit

Harvard Microrobotics Laboratory

Journal

Science Robotics

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

A springtail-inspired multi-modal walking-jumping microrobot

Article Publication Date

26-Feb-2025

 

Mantis shrimp clubs filter sound to mitigate damage

Patterned armor selectively blocks high-frequency stress waves

Northwestern University

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A mantis shrimp shows its dactyl clubs (in greenish yellow).

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Credit: Andy Law

Known for their powerful punch, mantis shrimp can smash a shell with the force of a .22 caliber bullet. Yet, amazingly, these tough critters remain intact despite the intense shockwaves created by their own strikes.

Northwestern University researchers have discovered how mantis shrimp remain impervious to their own punches. Their fists, or dactyl clubs, are covered in layered patterns, which selectively filter out sound. By blocking specific vibrations, the patterns act like a shield against self-generated shockwaves.

The study will be published on Friday (Feb. 7) in the journal Science.

The findings someday could be applied to developing synthetic, sound-filtering materials for protective gear as well as inspire new approaches to reducing blast-related injuries in military and sports.

“The mantis shrimp is known for its incredibly powerful strike, which can break mollusk shells and even crack aquarium glass,” said Northwestern’s Horacio D. Espinosa, the study’s co-corresponding author. “However, to repeatedly execute these high-impact strikes, the mantis shrimp’s dactyl club must have a robust protection mechanism to prevent self-damage. Most prior work has focused on the club’s toughness and crack resistance, treating the structure as a toughened impact shield. We found it uses phononic mechanisms — structures that selectively filter stress waves. This enables the shrimp to preserve its striking ability over multiple impacts and prevent soft tissue damage.”

An expert on bio-inspired materials, Espinosa is the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship and a professor of mechanical engineering at Northwestern’s McCormick School of Engineering, where he directs the Institute for Cellular Engineering Technologies. Espinosa led the study in partnership with M. Abi Ghanem of the Institute of Light and Matter, a joint research unit between Claude-Bernard-Lyon-I University and the Center for National Scientific Research in France.

A devastating blow

Living in shallow, tropical waters, mantis shrimp are armed with one hammer-like dactyl club on each side of its body. These clubs store energy in elastic, spring-like structures, which are held in place by latch-like tendons. When the latch is released, the stored energy, too, is released — propelling the club forward with explosive force.

With a single blow, mantis shrimp can slaughter prey or defend their territory from interloping competitors. As the punch rips through surrounding water, it creates a low-pressure zone behind it, causing a bubble to form.

“When the mantis shrimp strikes, the impact generates pressure waves onto its target,” Espinosa said. “It also creates bubbles, which rapidly collapse to produce shockwaves in the megahertz range. The collapse of these bubbles releases intense bursts of energy, which travel through the shrimp’s club. This secondary shockwave effect, along with the initial impact force, makes the mantis shrimp’s strike even more devastating.”

Protective patterns

Surprisingly, this force does not damage the shrimp’s delicate nerves and tissues, which are encased within its armor. 

To investigate this phenomenon, Espinosa and colleagues used two advanced techniques to examine the mantis shrimp’s armor in fine detail. First, they applied transient grating spectroscopy, a laser-based method that analyzes how stress waves propagate through materials. Second, they employed picosecond laser ultrasonics, which provide further insights into the armor’s microstructure.

Their experiments revealed two distinct regions — each engineered for a specific function — within the mantis shrimp’s club. The impact region, responsible for delivering crushing blows, consists of mineralized fibers arranged in a herringbone pattern, giving it resistance to failure. Beneath this layer, the periodic region features twisted, corkscrew-like fiber bundles. These bundles form a Bouligand structure, a layered arrangement, in which each layer is progressively rotated relative to its neighbors.

While the herringbone pattern reinforces the club against fractures, the corkscrew arrangement governs how stress waves travel through the structure. This intricate design acts as a phononic shield, selectively filtering high-frequency stress waves to prevent damaging vibrations from propagating back into the shrimp’s arm and body.

“The periodic region plays a crucial role in selectively filtering out high-frequency shear waves, which are particularly damaging to biological tissues” Espinosa said. “This effectively shields the shrimp from damaging stress waves caused by the direct impact and bubble collapse.”

In this study, the researchers analyzed 2D simulations of wave behavior. Espinosa said 3D simulations are needed to fully understand the club’s complex structure.

“Future research should focus on more complex 3D simulations to fully capture how the club’s structure interacts with shockwaves,” Espinosa said. “Additionally, designing aquatic experiments with state-of-the-art instrumentation would allow us to investigate how phononic properties function in submerged conditions.”

The study, “Does the mantis shrimp pack a phononic shield?” was supported by the Air Force Office of Scientific Research, the Office of Naval Research and the National Science Foundation.

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Journal

Science

DOI

10.1126/science.adq7100 

Article Title

Does the mantis shrimp pack a phononic shield?

Article Publication Date

7-Feb-2025

 

Taco-shaped arthropod from Royal Ontario Museum’s Burgess Shale fossils gives new insights into the history of the first mandibulates

Exceptional fossils show how mandibulates were trapping prey in marine ecosystems 500 million years ago

TODAY'S MANTIS SHRIMP

ROYAL ONTARIO MUSEUM

 

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RESEARCHERS BELIEVE ODARAIA COULD HAVE SWUM UPSIDE DOWN TO GATHER FOOD AMONG ITS MANY SPINES ALONG ITS LEGS.

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CREDIT: ILLUSTRATED BY DANIELLE DUFAULT. COURTESY ROYAL ONTARIO MUSEUM

A new study, led by palaeontologists at the Royal Ontario Museum (ROM) is helping resolve the evolution and ecology of Odaraia, a taco-shaped marine animal that lived during the Cambrian period. Fossils collected by ROM reveal Odaraia had mandibles. Palaeontologists are finally able to place it as belonging to the mandibulates, ending its long enigmatic classification among the arthropods since it was first discovered in the Burgess Shale over 100 years ago and revealing more about early evolution and diversification. The study The Cambrian Odaraia alata and the colonization of nektonic suspension-feeding niches by early mandibulates was published in the journal Proceedings B.

The study authors were able to identify a pair of large appendages with grasping jagged edges near its mouth, clearly indicative of mandibles which are one of the key and distinctive features of the mandibulate group of animals. This suggests that Odaraia was one of the earliest known members of this group. The researchers made another stunning discovery, a detailed analysis of its more than 30 pairs of legs, found an intricate system of small and large spines. According to the authors, these spines could intertwine, capturing smaller prey as though a fishing net, suggesting how some of these first mandibulates left the sea floor and explored the water column, setting the seeds for their future ecological success.

“The head shield of Odaraia envelops practically half of its body including its legs, almost as if it were encased in a tube. Previous researchers had suggested this shape would have allowed Odaraia to gather its prey, but the capturing mechanism had eluded us, until now,” says Alejandro Izquierdo-López, lead author, who was based at ROM during this work as a PhD student at the University of Toronto. “Odaraia had been beautifully described in the 1980s, but given the limited number of fossils at that time and its bizarre shape, two important questions had remained unanswered: is it really a mandibulate? And what was it feeding on?”

At almost 20 cm in size, the authors explain that early mandibulates like Odaraia were part of a community of large animals that could have been able to migrate from the marine bottom-dwelling ecosystems characteristic of the Cambrian period to the upper layers of the water column. These types of communities could have enriched the water column and facilitated a transition towards more complex ecosystems.

Cambrian fossils record the major divergence of animal groups originating over 500 million years ago. This period saw the evolution of innumerable innovations, such as eyes, legs or shells, and the first diversification of many animal groups, including the mandibulates, one of the major groups of arthropods (animals with jointed limbs).

Mandibulates are an example of evolutionary success, representing over half of all current species on Earth. Today, mandibulates are everywhere: from sea-dwelling crabs to centipedes lurking in the undergrowth or bees flying across meadows, but their beginnings were more humble. During the Cambrian period, the first mandibulates were marine animals, most bearing distinct head shields or carapaces.

“The Burgess Shale has been a treasure trove of paleontological information,” says Jean-Bernard Caron, Richard Ivey Curator at the Royal Ontario Museum, and co-author of the study. “Thanks to the work we have been doing at the ROM on amazing fossil animals such as Tokummia and Waptia, we already know a substantial amount about the early evolution of mandibulates. However, some other species had remained quite enigmatic, like Odaraia.”

The Royal Ontario Museum holds the largest collections of Cambrian fossils from the world-renowned Burgess Shale of British Columbia. Burgess Shale fossils are exceptional, as they preserve structures, animals and ecosystems that under normal conditions would have decayed and completely disappeared from the fossil record. Mandibulates, though, are generally rare in the fossil record. Most fossils preserve only the hard parts of animals, such as skeletons or the mineralized cuticles of the well-known trilobites, structures that mandibulates lack.

For over forty years Odaraia has been one of the most iconic animals of the Burgess Shale, with its distinctive taco-shaped carapace, its large head and eyes, and a tail that resembles a submarine's keel. The public can view specimens of Odaraia on display at the Willner Madge Gallery, Dawn of Life at the Royal Ontario Museum.

Photos of Odaraia fossil, ROMIP 60746.

CREDIT

Photo by Jean-Bernard Caron, Royal Ontario Museum.

Fossil of Odaraia ROMIP 952413_1.

CREDIT

Jean-Bernard Caron, Royal Ontario Museum

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JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2024.0622 

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

The Cambrian Odaraia alata and the colonization of nektonic suspension-feeding niches by early mandibulates

ARTICLE PUBLICATION DATE

23-Jul-2024

 

Seeing the unseen: How butterflies can help scientists detect cancer

Peer-Reviewed Publication

UNIVERSITY OF ILLINOIS GRAINGER COLLEGE OF ENGINEERING

 

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ARTISTIC DEPICTION OF A BUTTERFLY ABOVE THE BIOINSPIRED IMAGING SENSOR

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CREDIT: THE GRAINGER COLLEGE OF ENGINEERING AT UNIVERSITY OF ILLINOIS URBANA-CHAMPAIGN

There are many creatures on our planet with more advanced senses than humans. Turtles can sense Earth’s magnetic field. Mantis shrimp can detect polarized light. Elephants can hear much lower frequencies than humans can. Butterflies can perceive a broader range of colors, including ultraviolet (UV) light.

Inspired by the enhanced visual system of the Papilio xuthus butterfly, a team of researchers have developed an imaging sensor capable of “seeing” into the UV range inaccessible to human eyes. The design of the sensor uses stacked photodiodes and perovskite nanocrystals (PNCs) capable of imaging different wavelengths in the UV range. Using the spectral signatures of biomedical markers, such as amino acids, this new imaging technology is even capable of differentiating between cancer cells and normal cells with 99% confidence.

This new research, led by University of Illinois Urbana-Champaign electrical and computer engineering professor Viktor Gruev and bioengineering professor Shuming Nie, was recently published in the journal Science Advances.

Small Variations

“We've taken inspiration from the visual system of butterflies, who are able to perceive multiple regions in the UV spectrum, and designed a camera that replicates that functionality,” Gruev says. “We did this by using novel perovskite nanocrystals, combined with silicon imaging technology, and this new camera technology can detect multiple UV regions.”

UV light is electromagnetic radiation with wavelengths shorter than that of visible light (but longer than x-rays). We are most familiar with UV radiation from the sun and the dangers it poses to human health. UV light is categorized into three different regions—UVA, UVB and UVC— based on different wavelength ranges. Because humans cannot see UV light, it is challenging to capture UV information, especially discerning the small differences between each region.

Butterflies, however, can see these small variations in the UV spectrum, like humans can see shades of blue and green. Gruev notes, “It is intriguing to me how they are able to see those small variations. UV light is incredibly difficult to capture, it just gets absorbed by everything, and butterflies have managed to do it extremely well.”

The Imitation Game

Humans have trichromatic vision with three photoreceptors, where every color perceived can be made from a combination of red, green and blue. Butterflies, however, have compound eyes, with six (or more) photoreceptor classes with distinct spectral sensitivities. In particular, the Papilio xuthus, a yellow, Asian swallowtail butterfly, has not only blue, green and red, but also violet, ultraviolet and broadband receptors. Further, butterflies have fluorescent pigments that allow them to convert UV light into visible light which can then be easily sensed by their photoreceptors. This allows them to perceive a broader range of colors and details in their environment.

Beyond the increased number of photoreceptors, butterflies also exhibit a unique tiered structure in their photoreceptors. To replicate the UV sensing mechanism of the Papilio xuthus butterfly, the UIUC team has emulated the process by combining a thin layer of PNCs with a tiered array of silicon photodiodes.

PNCs are a class of semiconductor nanocrystals that display unique properties similar to that of quantum dots—changing the size and composition of the particle changes the absorption and emission properties of the material. In the last few years, PNCs have emerged as an interesting material for different sensing applications, such as solar cells and LEDs. PNCs are extremely good at detecting UV (and even lower) wavelengths that traditional silicon detectors are not. In the new imaging sensor, the PNC layer is able to absorb UV photons and re-emit light in the visible (green) spectrum which is then detected by the tiered silicon photodiodes. Processing of these signals allows for mapping and identification of UV signatures.

Healthcare and Beyond

There are various biomedical markers present in cancerous tissues at higher concentrations than in healthy tissues—amino acids (building blocks of proteins), proteins, and enzymes. When excited with UV light, these markers light up and fluoresce in the UV and part of the visible spectrum, in a process called autofluorescence. “Imaging in the UV region has been limited and I would say that has been the biggest roadblock for making scientific progress,” explains Nie. “Now we have come up with this technology where we can image UV light with high sensitivity and can also distinguish small wavelength differences.”

Because cancer and healthy cells have different concentrations of markers and therefore different spectral signatures, the two classes of cells can be differentiated based on their fluorescence in the UV spectrum. The team evaluated their imaging device on its ability to discriminate cancer-related markers and found that is capable of differentiating between cancer and healthy cells with 99% confidence.

Gruev, Nie and their collaborative research team envision being able to use this sensor during surgery. One of the biggest challenges is knowing how much tissue to remove to ensure clear margins and such a sensor can help facilitate the decision-making process when a surgeon is removing a cancerous tumor.

“This new imaging technology is enabling us to differentiate cancerous versus healthy cells and is opening up new and exciting applications beyond just health,” Nie says. There are many other species besides butterflies capable of seeing in the UV, and having a way to detect that light will provide interesting opportunities for biologists to learn more about these species, such as their hunting and mating habits. Bringing the sensor underwater can help bring a greater understanding of that environment as well. While a lot of UV is absorbed by water, there is still enough that makes it through to have an impact and there are many animals underwater that also see and use UV light.  

***

Viktor Gruev is also an affiliate of Beckman Institute for Advanced Science and Technology, the department of bioengineering and the Carle Illinois College of Medicine at UIUC.

Shuming Nie is also an affiliate of Beckman Institute for Advanced Science and Technology, and the department of electrical and computer engineering.

Other contributors to this work include Cheng Chen (department of electrical and computer engineering at UIUC), Ziwen Wang (department of bioengineering at UIUC), Jiajing Wu (College of Engineering and Applied Sciences at Nanjing University, China and School of Chemistry and Chemical Engineering at Yangzhou University, China), Zhengtao Deng (College of Engineering and Applied Sciences at Nanjing University, China), Tao Zhang (College of Engineering and Applied Sciences at Nanjing University, China), Zhongmin Zhu (department of electrical and computer engineering at UIUC), Yifei Jin (department of electrical and computer engineering at UIUC), Benjamin Lew (department of electrical and computer engineering at UIUC), Indrajit Srivastava (department of electrical and computer engineering at UIUC) and Zuodong Liang (department of electrical and computer engineering at UIUC).

This research was funded by the U.S. Air Force Office of Scientific Research, Office of Naval Research, the National Science Foundation, the National Institute of Health, and the University of Illinois Institutional Funds.

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JOURNAL

Science Advances

DOI

10.1126/sciadv.adk3860 

ARTICLE PUBLICATION DATE

3-Nov-2023