Blood-powered toes give salamanders an arboreal edge
Washington State University
image:
Still frame image showing the hindfoot of a live Wandering Salamander (Aneides vagrans) from a ventral perspective just before the salamander takes a step forward. This image shows the large digital blood sinuses and the points at which they connect near the distal-most joint.
view moreCredit: Photo by William P. Goldenberg
PULLMAN, Wash. — Wandering salamanders are known for gliding high through the canopies of coastal redwood forests, but how the small amphibians stick their landing and take-off with ease remains something of a mystery.
A new study in the Journal of Morphology reveals the answer may have a lot to do with a surprising mechanism: blood-powered toes. The Washington State University-led research team discovered that wandering salamanders (Aneides vagrans) can rapidly fill, trap, and drain the blood in their toe tips to optimize attachment, detachment and general locomotion through their arboreal environment.
The research not only uncovers a previously unknown physiological mechanism in salamanders but also has implications for bioinspired designed. Insights into salamander toe mechanics could ultimately inform the development of adhesives, prosthetics, and even robotic appendages.
“Gecko-inspired adhesives already allow surfaces to be reused without losing stickiness,” said Christian Brown, lead author of the study and an integrative physiology and neuroscience postdoctoral researcher at WSU. “Understanding salamander toes could lead to similar breakthroughs in attachment technologies.”
Discovery sparked by a documentary shoot
Salamanders of the Aneides genus have long puzzled scientists with their square-shaped toe tips and bright red blood “lakes” that can be seen just beneath their translucent skin. Historically, these features were thought to aid oxygenation, but no evidence supported that claim.
Brown’s interest in the topic traces back to an unexpected observation during the filming of the documentary, “The Americas,” which airs on Feb. 23 on NBC and Peacock. While assisting on set as the resident salamander expert, Brown had the opportunity to observe through the production team’s high-powered camera lenses how the amphibians move around.
He noticed something strange. Blood was rushing into the small creatures’ translucent toe tips moments before they took a step. Brown and camera assistant William Goldenberg repeatedly observed the phenomenon. “We looked at each other like, ‘Did you see that?’” Brown said.
Though the producers moved on, Brown’s curiosity didn’t. After the shoot, he reached out to Goldenberg and asked if he was interested in using his film equipment to investigate what they had observed in a scientific and repeatable way.
Through high-resolution video trials and corroborating analysis in WSU’s Franceschi Microscopy & Imaging Center, Brown, Goldenberg and colleagues at WSU and Gonzaga University uncovered that wandering salamanders can finely control and regulate blood flow to each side of their toe tips.
This allows them to adjust pressure asymmetrically, improving grip on irregular surfaces like tree bark. Surprisingly, the blood rushing in before “toe off” appears to help salamanders detach rather than attach. By slightly inflating the toe tip, the salamanders reduce the surface area in contact with the surface they are on, minimizing the energy required to let go. This dexterity is crucial for navigating the uneven and slippery surfaces of the redwood canopy—and for sticking safe landings when parachuting between branches.
“If you’re climbing a redwood and have 18 toes gripping bark, being able to detach efficiently without damaging your toe tips makes a huge difference,” Brown said.
The implications of the research could extend beyond Aneides vagrans. Similar vascularized structures are found in other salamander species, including aquatic ones, suggesting a universal mechanism for toe stiffness regulation that may serve different purposes depending on the salamander’s environment. Moving forward, Brown and colleagues plan to expand the research to look at how the mechanism works in other salamander species and habitats.
“This could redefine our understanding of how salamanders move across diverse habitats,” Brown said.
Salamanderoncamera 
A Wandering Salamander (Aneides vagrans) clings to a camera lens with a single forelimb after leaping onto the lens during scientific investigation of their jumping, parachuting, and gliding behaviors.
Credit
Photo by Christian Brown
Wanderingsalamander2 
A Wandering Salamander (Aneides vagrans) stands/clings to a horizontal/vertical surface while a camera and high-powered lens capture the blood activity within the toes.
Credit
Photo by Christian Brown
Journal
Journal of Morphology
Article Title
Vascular and Osteological Morphology of Expanded Digit Tips Suggests Specialization in the Wandering Salamander (Aneides vagrans)
Walk like a … gecko? Animal footpads inspire a polymer that sticks to ice
American Chemical Society
A solution to injuries from slips and falls may be found underfoot — literally. The footpads of geckos have hydrophilic (water-loving) mechanisms that allow the little animals to easily move over moist, slick surfaces. Researchers in ACS Applied Materials & Interfaces report using silicone rubber enhanced with zirconia nanoparticles to create a gecko-inspired slip-resistant polymer. They say the material, which sticks to ice, could be incorporated into shoe soles to reduce injuries in humans.
Slips and falls account for more than 38 million injuries and 684,000 deaths every year, according to the World Health Organization. And nearly half of these incidents happen on ice. Current anti-slip shoe soles rely on materials such as natural rubber that repel the layer of liquid water that sits atop pavement on a rainy day. On frozen walkways, however, shoe soles with these materials can cause ice to melt because of pressure from the wearer, creating the slippery surface the shoes are supposed to protect against.
Previous studies of gecko feet have led to new ideas for developing more effective anti-slip polymers. Those works found that their footpad’s stickiness comes from hydrophilic capillary-enhanced adhesion: The force of water being drawn into narrow grooves in the footpad creates suction that helps the lizard navigate slippery surfaces. Vipin Richhariya, Ashis Tripathy, Md Julker Nine and colleagues aimed to develop a polymer with capillary-enhanced adhesion that works on rainy sidewalks and frozen surfaces.
The researchers started with silicone rubber polymer and added zirconia nanoparticles to make the material attract water molecules. After they rolled the composite material into a thin film, they hardened it with heat and laser-etched a grooved pattern onto the film’s surface that exposed the hydrophilic zirconia nanoparticles. When the film encountered water molecules atop ice, it stuck to the slippery surface because the polymer mimicked the capillary action of slip-resistant gecko footpads. They tested five versions of the patterned nanocomposite material with different proportions of zirconia nanoparticles by weight: 1%, 3%, 5%, 7%, and 9%.
Using infrared spectroscopy and simulated friction tests, the researchers found that the most slip-resistant nanocomposites contained 3% and 5% zirconia nanoparticles by weight. In addition to a nature-inspired anti-slip shoe sole, the team says this technology could be used in medical innovations, such as electronic skin and artificial skin, where polymers interact with a layer of fluid between two different surfaces.
The authors acknowledge funding from the Foundation for Science and Technology, Portugal.
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The American Chemical Society (ACS) is a nonprofit organization founded in 1876 and chartered by the U.S. Congress. ACS is committed to improving all lives through the transforming power of chemistry. Its mission is to advance scientific knowledge, empower a global community and champion scientific integrity, and its vision is a world built on science. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, e-books and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.
Registered journalists can subscribe to the ACS journalist news portal on EurekAlert! to access embargoed and public science press releases. For media inquiries, contact newsroom@acs.org.
Note: ACS does not conduct research but publishes and publicizes peer-reviewed scientific studies.
A solution to injuries from slips and falls may be found underfoot — literally. The footpads of geckos have hydrophilic (water-loving) mechanisms that allow the little animals to easily move over moist, slick surfaces. Researchers in ACS Applied Materials & Interfaces report using silicone rubber enhanced with zirconia nanoparticles to create a gecko-inspired slip-resistant polymer. They say the material, which sticks to ice, could be incorporated into shoe soles to reduce injuries in humans.
Slips and falls account for more than 38 million injuries and 684,000 deaths every year, according to the World Health Organization. And nearly half of these incidents happen on ice. Current anti-slip shoe soles rely on materials such as natural rubber that repel the layer of liquid water that sits atop pavement on a rainy day. On frozen walkways, however, shoe soles with these materials can cause ice to melt because of pressure from the wearer, creating the slippery surface the shoes are supposed to protect against.
Previous studies of gecko feet have led to new ideas for developing more effective anti-slip polymers. Those works found that their footpad’s stickiness comes from hydrophilic capillary-enhanced adhesion: The force of water being drawn into narrow grooves in the footpad creates suction that helps the lizard navigate slippery surfaces. Vipin Richhariya, Ashis Tripathy, Md Julker Nine and colleagues aimed to develop a polymer with capillary-enhanced adhesion that works on rainy sidewalks and frozen surfaces.
The researchers started with silicone rubber polymer and added zirconia nanoparticles to make the material attract water molecules. After they rolled the composite material into a thin film, they hardened it with heat and laser-etched a grooved pattern onto the film’s surface that exposed the hydrophilic zirconia nanoparticles. When the film encountered water molecules atop ice, it stuck to the slippery surface because the polymer mimicked the capillary action of slip-resistant gecko footpads. They tested five versions of the patterned nanocomposite material with different proportions of zirconia nanoparticles by weight: 1%, 3%, 5%, 7%, and 9%.
Using infrared spectroscopy and simulated friction tests, the researchers found that the most slip-resistant nanocomposites contained 3% and 5% zirconia nanoparticles by weight. In addition to a nature-inspired anti-slip shoe sole, the team says this technology could be used in medical innovations, such as electronic skin and artificial skin, where polymers interact with a layer of fluid between two different surfaces.
The authors acknowledge funding from the Foundation for Science and Technology, Portugal.
###
The American Chemical Society (ACS) is a nonprofit organization founded in 1876 and chartered by the U.S. Congress. ACS is committed to improving all lives through the transforming power of chemistry. Its mission is to advance scientific knowledge, empower a global community and champion scientific integrity, and its vision is a world built on science. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, e-books and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.
Registered journalists can subscribe to the ACS journalist news portal on EurekAlert! to access embargoed and public science press releases. For media inquiries, contact newsroom@acs.org.
Note: ACS does not conduct research but publishes and publicizes peer-reviewed scientific studies.
Journal
ACS Applied Materials & Interfaces
ACS Applied Materials & Interfaces
DOI
Article Title
“Capillary-Enhanced Biomimetic Adhesion on Icy Surfaces for High-Performance Antislip Shoe-Soles”
“Capillary-Enhanced Biomimetic Adhesion on Icy Surfaces for High-Performance Antislip Shoe-Soles”
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