Tag Archives: geckos

Gecko-like toes needed for climbing robots

Caption: The spotted belly of a Tokay gecko used by UC Berkeley biologists to understand how the animal’s five sticky toes help it climb on many types of surface. Credit: Yi Song

Those are fabulous toes. Geckos and the fine hairs on their toes have been of great interest to researchers looking to increase qualities of adhesion for all kinds of purposes including for robots that climb. The latest foray into the research suggests that it’s not just the fine hairs found on gecko toes that are important.

A May 8, 2020 news item on ScienceDaily makes the proclamation,

Robots with toes? Experiments suggest that climbing robots could benefit from having flexible, hairy toes, like those of geckos, that can adjust quickly to accommodate shifting weight and slippery surfaces.

Biologists from the University of California, Berkeley, and Nanjing University of Aeronautics and Astronautics observed geckos running horizontally along walls to learn how they use their five toes to compensate for different types of surfaces without slowing down.

Close-up look at the toe pads of a Tokay gecko. They have about 15,000 hairs per foot, each of which has split ends that maximize contact with the surface and support the animal’s weight by interacting with surface molecules via van der Waals forces. (Photo by Yi Song)

You can find that image and more embedded in the May 8, 2020 University of California at Berkeley news release (also on EurekAlert) by Robert Sanders. The news release delves further into the work

“The research helped answer a fundamental question: Why have many toes?” said Robert Full, UC Berkeley professor of integrative biology.

As his previous research showed, geckos’ toes can stick to the smoothest surfaces through the use of intermolecular forces, and uncurl and peel in milliseconds. Their toes have up to 15,000 hairs per foot, and each hair has “an awful case of split ends, with as many as a thousand nano-sized tips that allow close surface contact,” he said.

These discoveries have spawned research on new types of adhesives that use intermolecular forces, or van der Waals forces, to stick almost anywhere, even underwater.

One puzzle, he said, is that gecko toes only stick in one direction. They grab when pulled in one direction, but release when peeled in the opposite direction. Yet, geckos move agilely in any orientation.

To determine how geckos have learned to deal with shifting forces as they move on different surfaces, Yi Song, a UC Berkeley visiting student from Nanjing, China, ran geckos sideways along a vertical wall while making high-speed video recordings to show the orientation of their toes. The sideways movement allowed him to distinguish downward gravity from forward running forces to best test the idea of toe compensation.

Using a technique called frustrated total internal reflection, Song, also measured the area of contact of each toe. The technique made the toes light up when they touched a surface.

To the researcher’s surprise, geckos ran sideways just as fast as they climbed upward, easily and quickly realigning their toes against gravity. The toes of the front and hind top feet during sideways wall-running shifted upward and acted just like toes of the front feet during climbing.

To further explore the value of adjustable toes, researchers added slippery patches and strips, as well as irregular surfaces. To deal with these hazards, geckos took advantage of having multiple, soft toes. The redundancy allowed toes that still had contact with the surface to reorient and distribute the load, while the softness let them conform to rough surfaces.

“Toes allowed agile locomotion by distributing control among multiple, compliant, redundant structures that mitigate the risks of moving on challenging terrain,” Full said. “Distributed control shows how biological adhesion can be deployed more effectively and offers design ideas for new robot feet, novel grippers and unique manipulators.”

The team, which also includes Zhendong Dai and Zhouyi Wang of the College of Mechanical and Electrical Engineering at Nanjing University of Aeronautics and Astronautics, published its findings this week in the journal Proceedings of the Royal Society B.

Here’s a link to and a citation for the paper,

Role of multiple, adjustable toes in distributed control shown by sideways wall-running in geckos by Yi Song, Zhendong Dai, Zhouyi Wang, and Robert J. Full. Proceedings of the Royal Society B; Biological Sciences 29 April 2020 Volume 287Issue 1926 DOI: https://doi.org/10.1098/rspb.2020.0123 Published [online]:06 May 2020

This paper is open access.

Gecko lets go!

After all these years of writing about geckos and their adhesive properties it seems that geckos sometimes slip or let go, theoretically. (BTW, there’s a Canadian connection’ one of  the researchers is at the University of Calgary in the province of Alberta.) From a July 19, 2017 Cornell University news release (also on EurekAlert),

Geckos climb vertically up trees, walls and even windows, thanks to pads on the digits of their feet that employ a huge number of tiny bristles and hooks.

Scientists have long marveled at the gecko’s adhesive capabilities, which have been described as 100 times more than what is needed to support their body weight or run quickly up a surface.

But a new theoretical study examines for the first time the limits of geckos’ gripping ability in natural contexts. The study, recently published in the Journal of the Royal Society Interface, reports there are circumstances – such as when geckos fear for their lives, leap into the air and are forced to grab on to a leaf below – when they need every bit of that fabled adhesive ability, and sometimes it’s not enough.

“Geckos are notoriously described as having incredible ability to adhere to a surface,” said Karl Niklas, professor of plant evolution at Cornell University and a co-author of the paper. The study’s lead authors, Timothy Higham at the University of California, Riverside, and Anthony Russell at the University of Calgary, Canada, both zoologists, brought Niklas into the project for his expertise on plant biomechanics.

“The paper shows that [adhesive capability] might be exaggerated, because geckos experience falls and a necessity to grip a surface like a leaf that requires a much more tenacious adhesion force; the paper shows that in some cases the adhesive ability can be exceeded,” Niklas said.

In the theoretical study, the researchers developed computer models to understand if there are common-place instances when the geckos’ ability to hold on to surfaces might be challenged, such as when canopy-dwelling geckos are being chased by a predator and are forced to leap from a tree, hoping to land on a leaf below. The researchers incorporated ecological observations, adhesive force measurements, and body size and shape measurements of museum specimens to conduct simulations. They also considered the biomechanics of the leaves, the size of the leaves and the angles on the surface that geckos might land on to determine impact forces. Calculations were also based on worst-case scenarios, where a gecko reaches a maximum speed when it is no longer accelerating, called “terminal settling velocity.”

“Leaves are cantilevered like diving boards and they go through harmonic motion [when struck], so you have to calculate the initial deflection and orientation, and then consider how does that leaf rebound and can the gecko still stay attached,” Niklas said.

The final result showed that in some cases geckos don’t have enough adhesion to save themselves, he added.

Higham and Russell are planning to travel to French Guiana to do empirical adhesive force studies on living geckos in native forests.

The basic research helps people better understand how geckos stick to surfaces, and has the potential for future applications that mimic such biological mechanisms.

Here’s a link to and a citation for the paper,

Leaping lizards landing on leaves: escape-induced jumps in the rainforest canopy challenge the adhesive limits of geckos by Timothy E. Higham, Anthony P. Russell, Karl J. Niklas. Journal of the Royal Society Interface June 2017 Volume 14, issue 131 DOI: 10.1098/rsif.2017.0156 Published 28 June 2017

I think the authors had some fun with that title. In any event, the paper is behind a paywall.

Cambridge University researchers tell us why Spiderman can’t exist while Stanford University proves otherwise

A team of zoology researchers at Cambridge University (UK) find themselves in the unenviable position of having their peer-reviewed study used as a source of unintentional humour. I gather zoologists (Cambridge) and engineers (Stanford) don’t have much opportunity to share information.

A Jan. 18, 2016 news item on ScienceDaily announces the Cambridge research findings,

Latest research reveals why geckos are the largest animals able to scale smooth vertical walls — even larger climbers would require unmanageably large sticky footpads. Scientists estimate that a human would need adhesive pads covering 40% of their body surface in order to walk up a wall like Spiderman, and believe their insights have implications for the feasibility of large-scale, gecko-like adhesives.

A Jan. 18, 2016 Cambridge University press release (also on EurekAlert), which originated the news item, describes the research and the thinking that led to the researchers’ conclusions,

Dr David Labonte and his colleagues in the University of Cambridge’s Department of Zoology found that tiny mites use approximately 200 times less of their total body area for adhesive pads than geckos, nature’s largest adhesion-based climbers. And humans? We’d need about 40% of our total body surface, or roughly 80% of our front, to be covered in sticky footpads if we wanted to do a convincing Spiderman impression.

Once an animal is big enough to need a substantial fraction of its body surface to be covered in sticky footpads, the necessary morphological changes would make the evolution of this trait impractical, suggests Labonte.

“If a human, for example, wanted to walk up a wall the way a gecko does, we’d need impractically large sticky feet – our shoes would need to be a European size 145 or a US size 114,” says Walter Federle, senior author also from Cambridge’s Department of Zoology.

The researchers say that these insights into the size limits of sticky footpads could have profound implications for developing large-scale bio-inspired adhesives, which are currently only effective on very small areas.

“As animals increase in size, the amount of body surface area per volume decreases – an ant has a lot of surface area and very little volume, and a blue whale is mostly volume with not much surface area” explains Labonte.

“This poses a problem for larger climbing species because, when they are bigger and heavier, they need more sticking power to be able to adhere to vertical or inverted surfaces, but they have comparatively less body surface available to cover with sticky footpads. This implies that there is a size limit to sticky footpads as an evolutionary solution to climbing – and that turns out to be about the size of a gecko.”

Larger animals have evolved alternative strategies to help them climb, such as claws and toes to grip with.

The researchers compared the weight and footpad size of 225 climbing animal species including insects, frogs, spiders, lizards and even a mammal.

“We compared animals covering more than seven orders of magnitude in weight, which is roughly the same as comparing a cockroach to the weight of Big Ben, for example,” says Labonte.

These investigations also gave the researchers greater insights into how the size of adhesive footpads is influenced and constrained by the animals’ evolutionary history.

“We were looking at vastly different animals – a spider and a gecko are about as different as a human is to an ant- but if you look at their feet, they have remarkably similar footpads,” says Labonte.

“Adhesive pads of climbing animals are a prime example of convergent evolution – where multiple species have independently, through very different evolutionary histories, arrived at the same solution to a problem. When this happens, it’s a clear sign that it must be a very good solution.”

The researchers believe we can learn from these evolutionary solutions in the development of large-scale manmade adhesives.

“Our study emphasises the importance of scaling for animal adhesion, and scaling is also essential for improving the performance of adhesives over much larger areas. There is a lot of interesting work still to do looking into the strategies that animals have developed in order to maintain the ability to scale smooth walls, which would likely also have very useful applications in the development of large-scale, powerful yet controllable adhesives,” says Labonte.

There is one other possible solution to the problem of how to stick when you’re a large animal, and that’s to make your sticky footpads even stickier.

“We noticed that within closely related species pad size was not increasing fast enough to match body size, probably a result of evolutionary constraints. Yet these animals can still stick to walls,” says Christofer Clemente, a co-author from the University of the Sunshine Coast [Australia].

“Within frogs, we found that they have switched to this second option of making pads stickier rather than bigger. It’s remarkable that we see two different evolutionary solutions to the problem of getting big and sticking to walls,” says Clemente.

“Across all species the problem is solved by evolving relatively bigger pads, but this does not seem possible within closely related species, probably since there is not enough morphological diversity to allow it. Instead, within these closely related groups, pads get stickier. This is a great example of evolutionary constraint and innovation.”

A researcher at Stanford University (US) took strong exception to the Cambridge team’s conclusions , from a Jan. 28, 2016 article by Michael Grothaus for Fast Company (Note: A link has been removed),

It seems the dreams of the web-slinger’s fans were crushed forever—that is until a rival university swooped in and saved the day. A team of engineers working with mechanical engineering graduate student Elliot Hawkes at Stanford University have announced [in 2014] that they’ve invented a device called “gecko gloves” that proves the Cambridge researchers wrong.

Hawkes has created a video outlining the nature of his dispute with Cambridge University and US tv talk show host, Stephen Colbert who featured the Cambridge University research in one of his monologues,

To be fair to Hawkes, he does prove his point. A Nov. 21, 2014 Stanford University report by Bjorn Carey describes Hawke’s ingenious ‘sticky pads,

Each handheld gecko pad is covered with 24 adhesive tiles, and each of these is covered with sawtooth-shape polymer structures each 100 micrometers long (about the width of a human hair).

The pads are connected to special degressive springs, which become less stiff the further they are stretched. This characteristic means that when the springs are pulled upon, they apply an identical force to each adhesive tile and cause the sawtooth-like structures to flatten.

“When the pad first touches the surface, only the tips touch, so it’s not sticky,” said co-author Eric Eason, a graduate student in applied physics. “But when the load is applied, and the wedges turn over and come into contact with the surface, that creates the adhesion force.”

As with actual geckos, the adhesives can be “turned” on and off. Simply release the load tension, and the pad loses its stickiness. “It can attach and detach with very little wasted energy,” Eason said.

The ability of the device to scale up controllable adhesion to support large loads makes it attractive for several applications beyond human climbing, said Mark Cutkosky, the Fletcher Jones Chair in the School of Engineering and senior author on the paper.

“Some of the applications we’re thinking of involve manufacturing robots that lift large glass panels or liquid-crystal displays,” Cutkosky said. “We’re also working on a project with NASA’s Jet Propulsion Laboratory to apply these to the robotic arms of spacecraft that could gently latch on to orbital space debris, such as fuel tanks and solar panels, and move it to an orbital graveyard or pitch it toward Earth to burn up.”

Previous work on synthetic and gecko adhesives showed that adhesive strength decreased as the size increased. In contrast, the engineers have shown that the special springs in their device make it possible to maintain the same adhesive strength at all sizes from a square millimeter to the size of a human hand.

The current version of the device can support about 200 pounds, Hawkes said, but, theoretically, increasing its size by 10 times would allow it to carry almost 2,000 pounds.

Here’s a link to and a citation for the Stanford paper,

Human climbing with efficiently scaled gecko-inspired dry adhesives by Elliot W. Hawkes, Eric V. Eason, David L. Christensen, Mark R. Cutkosky. Jurnal of the Royal Society Interface DOI: 10.1098/rsif.2014.0675 Published 19 November 2014

This paper is open access.

To be fair to the Cambridge researchers, It’s stretching it a bit to say that Hawke’s gecko gloves allow someone to be like Spiderman. That’s a very careful, slow climb achieved in a relatively short period of time. Can the human body remain suspended that way for more than a few minutes? How big do your sticky pads have to be if you’re going to have the same wall-climbing ease of movement and staying power of either a gecko or Spiderman?

Here’s a link to and a citation for the Cambridge paper,

Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing by David Labonte, Christofer J. Clemente, Alex Dittrich, Chi-Yun Kuo, Alfred J. Crosby, Duncan J. Irschick, and Walter Federle. PNAS doi: 10.1073/pnas.1519459113

This paper is behind a paywall but there is an open access preprint version, which may differ from the PNAS version, available,

Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing by David Labonte, Christofer J Clemente, Alex Dittrich, Chi-Yun Kuo, Alfred J Crosby, Duncan J Irschick, Walter Federle. bioRxiv
doi: http://dx.doi.org/10.1101/033845

I hope that if the Cambridge researchers respond, they will be witty rather than huffy. Finally, there’s this gecko image (which I love) from the Cambridge researchers,

 Caption: This image shows a gecko and ant. Credit: Image courtesy of A Hackmann and D Labonte

Caption: This image shows a gecko and ant. Credit: Image courtesy of A Hackmann and D Labonte

Commercializing nanotechnology: Peter Thiel’s Breakout Labs and Argonne National Laboratories

Breakout Labs

I last wrote about entrepreneur Peter Thiel’s Breakout Labs project in an Oct. 26, 2011 posting announcing its inception. An Oct. 6, 2015 Breakout Labs news release (received in my email) highlights a funding announcement for four startups of which at least three are nanotechnology-enabled,

Breakout Labs, a program of Peter Thiel’s philanthropic organization, the Thiel Foundation, announced today that four new companies advancing scientific discoveries in biomedical, chemical engineering, and nanotechnology have been selected for funding.

“We’re always hearing about bold new scientific research that promises to transform the world, but far too often the latest discoveries are left withering in a lab,” said Lindy Fishburne, Executive Director of Breakout Labs. “Our mission is to help a new type of scientist-entrepreneur navigate the startup ecosystem and build lasting companies that can make audacious scientific discoveries meaningful to everyday life. The four new companies joining the Breakout Labs portfolio – nanoGriptech, Maxterial, C2Sense, and CyteGen – embody that spirit and we’re excited to be working with them to help make their vision a reality.”

The future of adhesives: inspired by geckos

Inspired by the gecko’s ability to scuttle up walls and across ceilings due to their millions of micro/nano foot-hairs,nanoGriptech (http://nanogriptech.com/), based in Pittsburgh, Pa., is developing a new kind of microfiber adhesive material that is strong, lightweight, and reusable without requiring glues or producing harmful residues. Currently being tested by the U.S. military, NASA, and top global brands, nanoGriptech’s flagship product Setex™ is the first adhesive product of its kind that is not only strong and durable, but can also be manufactured at low cost, and at scale.

“We envision a future filled with no-leak biohazard enclosures, ergonomic and inexpensive car seats, extremely durable aerospace adhesives, comfortable prosthetic liners, high performance athletic wear, and widely available nanotechnology-enabled products manufactured less expensively — all thanks to the grippy little gecko,” said Roi Ben-Itzhak, CFO and VP of Business Development for nanoGriptech.

A sense of smell for the digital world

Despite the U.S. Department of Agriculture’s recent goals to drastically reduce food waste, most consumers don’t realize the global problem created by 1.3 billion metric tons of food wasted each year — clogging landfills and releasing unsustainable levels of methane gas into the atmosphere. Using technology developed at MIT’s Swager lab, Cambridge, Ma.-based C2Sense(http://www.c2sense.com/) is developing inexpensive, lightweight hand-held sensors based on carbon nanotubes which can detect fruit ripeness and meat, fish and poultry freshness. Smaller than a half of a business card, these sensors can be developed at very low cost, require very little power to operate, and can be easily integrated into most agricultural supply chains, including food storage packaging, to ensure that food is picked, stored, shipped, and sold at optimal freshness.

“Our mission is to bring a sense of smell to the digital world. With our technology, that package of steaks in your refrigerator will tell you when it’s about to go bad, recommend some recipe options and help build out your shopping list,” said Jan Schnorr, Chief Technology Officer of C2Sense.

Amazing metals that completely repel water

MaxterialTM, Inc. develops amazing materials that resist a variety of detrimental environmental effects through technology that emulates similar strategies found in nature, such as the self-cleaning lotus leaf and antifouling properties of crabs. By modifying the surface shape or texture of a metal, through a method that is very affordable and easy to introduce into the existing manufacturing process, Maxterial introduces a microlayer of air pockets that reduce contact surface area. The underlying material can be chemically the same as ever, retaining inherent properties like thermal and electrical conductivity. But through Maxterial’s technology, the metallic surface also becomes inherently water repellant. This property introduces the superhydrophobic maxterial as a potential solution to a myriad of problems, such as corrosion, biofouling, and ice formation. Maxterial is currently focused on developing durable hygienic and eco-friendly anti-corrosion coatings for metallic surfaces.

“Our process has the potential to create metallic objects that retain their amazing properties for the lifetime of the object – this isn’t an aftermarket coating that can wear or chip off,” said Mehdi Kargar, Co-founder and CEO of Maxterial, Inc. “We are working towards a day when shipping equipment can withstand harsh arctic environments, offshore structures can resist corrosion, and electronics can be fully submersible and continue working as good as new.”

New approaches to combat aging

CyteGen (http://cytegen.com/) wants to dramatically increase the human healthspan, tackle neurodegenerative diseases, and reverse age-related decline. What makes this possible now is new discovery tools backed by the dream team of interdisciplinary experts the company has assembled. CyteGen’s approach is unusually collaborative, tapping into the resources and expertise of world-renowned researchers across eight major universities to focus different strengths and perspectives to achieve the company’s goals. By approaching aging from a holistic, systematic point of view, rather than focusing solely on discrete definitions of disease, they have developed a new way to think about aging, and to develop treatments that can help people live longer, healthier lives.

“There is an assumption that aging necessarily brings the kind of physical and mental decline that results in Parkinson’s, Alzheimer’s, and other diseases. Evidence indicates otherwise, which is what spurred us to launch CyteGen,” said George Ugras, Co-Founder and President of CyteGen.

To date, Breakout Labs has invested in more than two dozen companies at the forefront of science, helping radical technologies get beyond common hurdles faced by early stage companies, and advance research and development to market much more quickly. Portfolio companies have raised more than six times the amount of capital invested in the program by the Thiel Foundation, and represent six Series A valuations ranging from $10 million to $60 million as well as one acquisition.

You can see the original Oct. 6, 2015 Breakout Labs news release here or in this Oct. 7, 2015 news item on Azonano.

Argonne National Labs and Nano Design Works (NDW) and the Argonne Collaborative Center for Energy Storage Science (ACCESS)

The US Department of Energy’s Argonne National Laboratory’s Oct. 6, 2015 press release by Greg Cunningham announced two initiatives meant to speed commercialization of nanotechnology-enabled products for the energy storage and other sectors,

Few technologies hold more potential to positively transform our society than energy storage and nanotechnology. Advances in energy storage research will revolutionize the way the world generates and stores energy, democratizing the delivery of electricity. Grid-level storage can help reduce carbon emissions through the increased adoption of renewable energy and use of electric vehicles while helping bring electricity to developing parts of the world. Nanotechnology has already transformed the electronics industry and is bringing a new set of powerful tools and materials to developers who are changing everything from the way energy is generated, stored and transported to how medicines are delivered and the way chemicals are produced through novel catalytic nanomaterials.

Recognizing the power of these technologies and seeking to accelerate their impact, the U.S. Department of Energy’s Argonne National Laboratory has created two new collaborative centers that provide an innovative pathway for business and industry to access Argonne’s unparalleled scientific resources to address the nation’s energy and national security needs. These centers will help speed discoveries to market to ensure U.S. industry maintains a lead in this global technology race.

“This is an exciting time for us, because we believe this new approach to interacting with business can be a real game changer in two areas of research that are of great importance to Argonne and the world,” said Argonne Director Peter B. Littlewood. “We recognize that delivering to market our breakthrough science in energy storage and nanotechnology can help ensure our work brings the maximum benefit to society.”

Nano Design Works (NDW) and the Argonne Collaborative Center for Energy Storage Science (ACCESS) will provide central points of contact for companies — ranging from large industrial entities to smaller businesses and startups, as well as government agencies — to benefit from Argonne’s world-class expertise, scientific tools and facilities.

NDW and ACCESS represent a new way to collaborate at Argonne, providing a single point of contact for businesses to assemble tailored interdisciplinary teams to address their most challenging R&D questions. The centers will also provide a pathway to Argonne’s fundamental research that is poised for development into practical products. The chance to build on existing scientific discovery is a unique opportunity for businesses in the nano and energy storage fields.

The center directors, Andreas Roelofs of NDW and Jeff Chamberlain of ACCESS, have both created startups in their careers and understand the value that collaboration with a national laboratory can bring to a company trying to innovate in technologically challenging fields of science. While the new centers will work with all sizes of companies, a strong emphasis will be placed on helping small businesses and startups, which are drivers of job creation and receive a large portion of the risk capital in this country.

“For a startup like mine to have the ability to tap the resources of a place like Argonne would have been immensely helpful,” said Roelofs. “We”ve seen the power of that sort of access, and we want to make it available to the companies that need it to drive truly transformative technologies to market.”

Chamberlain said his experience as an energy storage researcher and entrepreneur led him to look for innovative approaches to leveraging the best aspects of private industry and public science. The national laboratory system has a long history of breakthrough science that has worked its way to market, but shortening that journey from basic research to product has become a growing point of emphasis for the national laboratories over the past couple of decades. The idea behind ACCESS and NDW is to make that collaboration even easier and more powerful.

“Where ACCESS and NDW will differ from the conventional approach is through creating an efficient way for a business to build a customized, multi-disciplinary team that can address anything from small technical questions to broad challenges that require massive resources,” Chamberlain said. “That might mean assembling a team with chemists, physicists, computer scientists, materials engineers, imaging experts, or mechanical and electrical engineers; the list goes on and on. It’s that ability to tap the full spectrum of cross-cutting expertise at Argonne that will really make the difference.”

Chamberlain is deeply familiar with the potential of energy storage as a transformational technology, having led the formation of Argonne’s Joint Center for Energy Storage Research (JCESR). The center’s years-long quest to discover technologies beyond lithium-ion batteries has solidified the laboratory’s reputation as one of the key global players in battery research. ACCESS will tap Argonne’s full battery expertise, which extends well beyond JCESR and is dedicated to fulfilling the promise of energy storage.

Energy storage research has profound implications for energy security and national security. Chamberlain points out that approximately 1.3 billion people across the globe do not have access to electricity, with another billion having only sporadic access. Energy storage, coupled with renewable generation like solar, could solve that problem and eliminate the need to build out massive power grids. Batteries also have the potential to create a more secure, stable grid for countries with existing power systems and help fight global climate disruption through adoption of renewable energy and electric vehicles.

Argonne researchers are pursuing hundreds of projects in nanoscience, but some of the more notable include research into targeted drugs that affect only cancerous cells; magnetic nanofibers that can be used to create more powerful and efficient electric motors and generators; and highly efficient water filtration systems that can dramatically reduce the energy requirements for desalination or cleanup of oil spills. Other researchers are working with nanoparticles that create a super-lubricated state and other very-low friction coatings.

“When you think that 30 percent of a car engine’s power is sacrificed to frictional loss, you start to get an idea of the potential of these technologies,” Roelofs said. “But it’s not just about the ideas already at Argonne that can be brought to market, it’s also about the challenges for businesses that need Argonne-level resources. I”m convinced there are many startups out there working on transformational ideas that can greatly benefit from the help of a place Argonne to bring those ideas to fruition. That is what has me excited about ACCESS and NDW.”

For more information on ACCESS, see: access.anl.gov

For more information on NDW, see: nanoworks.anl.gov

You can read more about the announcement in an Oct. 6, 2015 article by Greg Watry for R&D magazine featuring an interview with Andreas Roelofs.

How geckos self-clean, even in dusty environments

An Australian research team claims a world first with regard to ‘gecko research’ according to a March 16, 2015* news item on ScienceDaily,

In a world first, a research team including James Cook University [JCU] scientists has discovered how geckos manage to stay clean, even in dusty deserts.

The process, described in Interface, a journal of the Royal Society, may also turn out to have important human applications.

JCU’s Professor Lin Schwarzkopf said the group found that tiny droplets of water on geckos, for instance from condensing dew, come into contact with hundreds of thousands of extremely small hair-like spines that cover the animals’ bodies.

A March 16, 2015 JCU press release (also on EurekAlert), which originated the news item, provides more detail,

“If you have seen how drops of water roll off a car after it is waxed, or off a couch that’s had protective spray used on it, you’ve seen the process happening,” she said. “The wax and spray make the surface very bumpy at micro and nano levels, and the water droplets remain as little balls, which roll easily and come off with gravity or even a slight wind.”

The geckos’ hair-like spines trap pockets of air and work on the same principle, but have an even more dramatic effect. Through a scanning electron microscope, tiny water droplets can be seen rolling into each other and jumping like popcorn off the skin of the animal as they merge and release energy.

Scientists were aware that hydrophobic surfaces repelled water, and that the rolling droplets helped clean the surfaces of leaves and insects, but this is the first time it has been documented in a vertebrate animal. Box-patterned geckos live in semi-arid habitats, with little rain but may have dew forming on them when the temperature drops overnight.

Professor Schwarzkopf said the process may help geckos keep clean, as the water can carry small particles of dust and dirt away from their body. “They tend to live in dry environments where they can’t depend on it raining, and this keeps process them clean,” she said.

She said there were possible applications for marine-based electronics that have to shed water quickly in use and for possible “superhydrophobic” clothing that would not get wet or dirty and would never need washing.

I’ve been reading about self-cleaning products for years now. (sigh) Where are they? Despite this momentary lapse into sighing and wailing, I am much encouraged that scientists are still trying to figure out how to create self-cleaning products.

Here’s a link to and a citation for the paper,

Removal mechanisms of dew via self-propulsion off the gecko skin by Gregory S. Watson, Lin Schwarzkopf, Bronwen W. Cribb, Sverre Myhra, Marty Gellender, and Jolanta A. Watson.
Interface, April 2015, Volume: 12 Issue: 105 DOI: 10.1098/rsif.2014.1396 Published 11 March 2015

This paper is open access.

*’2014′ corrected to ‘2015’ on Feb. 28, 2017.

Fish that suck and why they matter

That headline is misleading, these fish (remoras) surprised scientists when research challenged longheld beliefs that they used suction to cling to various surfaces  From a Feb. 12, 2015 news item on ScienceDaily,

How does the hitchhiking, flat-headed remora fish attach to surfaces so securely yet release so easily? Suction was thought to be the easy answer, but Brooke Flammang, a biologist at the New Jersey Institute of Technology (NJIT), has proved this long-held conclusion to be only partly true.

Here’s an image of a remora clinging to a glass or plexiglass (?) wall,

Remoras stick to fast-moving sea creatures, but are also content to cling to aquarium tank walls. Courtesy: NJIT

Remoras stick to fast-moving sea creatures, but are also content to cling to aquarium tank walls. Courtesy: NJIT

A Feb. 12, 2015 NJIT press release (also on EurekAlert), which originated the news item, describes this research in the field of biomimicry,

Researchers have long studied animals like tree frogs, geckos, and spiders for their adhesive abilities, but what makes remoras unique in this group is they combine three key elements: the ability to securely fasten themselves for long periods of time; attach to different types of surfaces; release quickly without harming the surface.

Understanding the mechanics of this process could help researchers and engineers create or improve designs for any number of devices that need to stick well but then release quickly without harming the host, such as tags for tracking endangered species or bandages that really don’t hurt when you pull them off.

Using footage captured by GoPro cameras at SeaWorld’s Discovery Cove in Orlando, Flammang and NJIT researchers found that the adhesive disc on the remora’s head used to attach to sharks, rays and other pelagic hosts is actually a complex mechanism that includes a modified fin structure with teeny spikes (called lamellar spinules) that generate friction to adhere to the host. Remora head anatomy also differs from other fish in having unusually-structured blood vessels that may be the secret to how they maintain adhesion for hours at a time.

What intrigued Flammang, who studies the locomotion of fishes, integrating sensory biology, physiology, fluid dynamics, and bio-inspired robotics, is how remoras can alter the position and shape of the plates within the disc to change their position or quickly let go. She was able to observe the minute movements of remora disc components through the underwater footage provided by marine videographers.

“Remoras attach to other organisms for a variety of reasons: To find food, get protection, and find mates. Because the animals they attach to are powerful swimmers, they need a durable attachment that won’t be compromised by the host organism’s swimming, bending body. The adhesive disc the remora evolved from dorsal fin elements acts as a specialized suction cup that can bend and won’t slip,” Flammang said.

“We are applying the biomechanics of this mechanism to a robotic prototype that will be able to adhere to both rough and smooth surfaces through a variety of challenging conditions, both in water and air,” she said.

Flammang presented her research at the Society for Integrative and Comparative Biology’s annual conference in January.

“We have a lot to learn from the natural world. Being able to examine these animals up close can be very valuable to bioengineering. We are proud to support this important work,” added SeaWorld Parks & Entertainment’s Vice President of Research and Science, Dr. Judy St. Leger.

“In my lab at NJIT, we study the morphology of remoras, how they use muscular and vascular control to manipulate the disc for attachment on different surfaces, and the hydrodynamics of their approach, attachment, and release from a surface,” Flammang said. “Live remoras swim in our flow tank – a treadmill for fish – and we capture muscle activity recordings and high speed video of the fish swimming and attaching, as well as and the fluid moving around the fish and the attachment location.”

More broadly, she examines the way organisms interact with marine and aquatic environments and drive the evolutionary selection of morphology and function. She seeks to understand, for example, how different fish fins may give an advantage to certain species in a given habitat.

The two remoras (Echeneis naucrates) at SeaWorld’s Discovery Cove were valuable candidates for this study because they often attach themselves to a large acrylic panel that divides their dock-themed habitat from the park’s Grand Reef, a nearly 1million gallon tropical environment. Aquarists at Discovery Cove donned scuba gear to capture the underwater footage using a GoPro camera steadied with a suction cup arm to get the shots needed by the research team. Flammang and her colleagues then used mathematical algorithms to visualize motion that is not detected by the human eye.

There doesn’t seem to be a published paper for this work.

Legos, geckos (van der Waals force), and single-atom sheets at the University of Kansas (US)

A Nov. 25, 2014 news item on Nanowerk describes the achievement,

Physicists at the University of Kansas have fabricated an innovative substance from two different atomic sheets that interlock much like Lego toy bricks. The researchers said the new material — made of a layer of graphene and a layer of tungsten disulfide — could be used in solar cells and flexible electronics. …

Hsin-Ying Chiu, assistant professor of physics and astronomy, and graduate student Matt Bellus fabricated the new material using “layer-by-layer assembly” as a versatile bottom-up nanofabrication technique. Then, Jiaqi He, a visiting student from China, and Nardeep Kumar, a graduate student who now has moved to Intel Corp., investigated how electrons move between the two layers through ultrafast laser spectroscopy in KU’s Ultrafast Laser Lab, supervised by Hui Zhao, associate professor of physics and astronomy.

“To build artificial materials with synergistic functionality has been a long journey of discovery,” Chiu said. “A new class of materials, made of the layered materials, has attracted extensive attention ever since the rapid development of graphene technology. One of the most promising aspects of this research is the potential to devise next-generation materials via atomic layer-level control over its electronic structure.”

A Nov. 25, 2014 University of Kansas news release (also on EurekAlert), which originated the news item, describes the problems and the new technique in more detail,

According to the researchers, the approach is to design synergistic materials by combining two single-atom thick sheets, for example, acting as a photovoltaic cell as well as a light-emitting diode, converting energy between electricity and radiation. However, combining layers of atomically thin material is a thorny task that has flummoxed researchers for years.

“A big challenge of this approach is that, most materials don’t connect together because of their different atomic arrangements at the interface — the arrangement of the atoms cannot follow the two different sets of rules at the same time,” Chiu said. “This is like playing with Legos of different sizes made by different manufacturers. As a consequence, new materials can only be made from materials with very similar atomic arrangements, which often have similar properties, too. Even then, arrangement of atoms at the interface is irregular, which often results in poor qualities.”

Layered materials such as those developed by the KU researchers provide a solution for this problem. Unlike conventional materials formed by atoms that are strongly bound in all directions, the new material features two layers where each atomic sheet is composed of atoms bound strongly with their neighbors — but the two atomic sheets are themselves only weakly linked to each other by the so-called van der Waals force, the same attractive phenomenon between molecules that allows geckos to stick to walls and ceilings.

“There exist about 100 different types of layered crystals — graphite is a well-known example,” Bellus said. “Because of the weak interlayer connection, one can choose any two types of atomic sheets and put one on top of the other without any problem. It’s like playing Legos with a flat bottom. There is no restriction. This approach can potentially product a large number of new materials with combined novel properties and transform the material science.”

Chiu and Bellus created the new carbon and tungsten disulfide material with the aim of developing novel materials for efficient solar cells. The single sheet of carbon atoms, known as graphene, excels at moving electrons around, while a single-layer of tungsten disulfide atoms is good at absorbing sunlight and converting it to electricity. By combining the two, this innovative material can potentially perform both tasks well.

The team used scotch tape to lift a single layer of tungsten disulfide atoms from a crystal and apply it to a silicon substrate. Next, they used the same procedure to remove a single layer of carbon atoms from a graphite crystal. With a microscope, they precisely laid the graphene on top of the tungsten disulfide layer. To remove any glue between the two atomic layers that are unintentionally introduced during the process, the material was heated at about 500 degrees Fahrenheit for a half-hour. This allowed the force between the two layers to squeeze out the glue, resulting in a sample of two atomically thin layers with a clean interface.

Doctoral students He and Kumar tested the new material in KU’s Ultrafast Laser Lab. The researchers used a laser pulse to excite the tungsten disulfide layer.

“We found that nearly 100 percent of the electrons that absorbed the energy from the laser pulse move from tungsten disulfide to graphene within one picosecond, or one-millionth of one-millionth second,” Zhao said. “This proves that the new material indeed combines the good properties of each component layer.”

The research groups led by Chiu and Zhao are trying to apply this Lego approach to other materials. For example, by combining two materials that absorb light of different colors, they can make materials that react to diverse parts of the solar spectrum.

Here’s a link to and a citation for the paper,

Electron transfer and coupling in graphene–​tungsten disulfide van der Waals heterostructures by Jiaqi He, Nardeep Kumar, Matthew Z. Bellus,     Hsin-Ying Chiu, Dawei He, Yongsheng Wang, & Hui Zhao. Nature Communications 5, Article number: 5622 doi:10.1038/ncomms6622 Published 25 November 2014

This paper is behind a paywall but there is a few preview available through ReadCube Access.

Climb like a gecko (in DARPA’s [US Defense Advanced Research Projects Agency] Z-Man program)

I’m not entirely certain why DARPA (US Defense Advanced Research Projects Agency) has now issued a news release (h/t June 5, 2014 news item on Nanowerk) about this achievement (a human climbing like a Gecko) which seems to have first occurred in 2012 but perhaps they want to emphasize that this particular demonstration occurred on a glass wall. In any event, I’m happy to get more news about DARPA’s Z-Man program. From the June 5, 2014 DARPA news release,

DARPA’s Z-Man program has demonstrated the first known human climbing of a glass wall using climbing devices inspired by geckos. The historic ascent involved a 218-pound climber ascending and descending 25 feet of glass, while also carrying an additional 50-pound load in one trial, with no climbing equipment other than a pair of hand-held, gecko-inspired paddles. [emphasis mine] The novel polymer microstructure technology used in those paddles was developed for DARPA by Draper Laboratory of Cambridge, Mass. [Massachusetts]

Historically, gaining the high ground has always been an operational advantage for warfighters, but the climbing instruments on which they’re frequently forced to rely—tools such as ropes and ladders—have not advanced significantly for millennia. Not only can the use of such tools be overt and labor intensive, they also only allow for sequential climbing whereby the first climber often takes on the highest risk.

DARPA created the Z-Man program to overcome these limitations and deliver maximum safety and flexibility for maneuver and rapid response to warfighters operating in tight urban environments. The goal of the program is to develop biologically inspired climbing aids to enable warfighters carrying a full combat load to scale vertical walls constructed from typical building materials.

“The gecko is one of the champion climbers in the Animal Kingdom, so it was natural for DARPA to look to it for inspiration in overcoming some of the maneuver challenges that U.S. forces face in urban environments,” said Dr. Matt Goodman, the DARPA program manager for Z-Man. “Like many of the capabilities that the Department of Defense pursues, we saw with vertical climbing that nature had long since evolved the means to efficiently achieve it. The challenge to our performer team was to understand the biology and physics in play when geckos climb and then reverse-engineer those dynamics into an artificial system for use by humans.”

Geckos can climb on a wide variety of surfaces, including smooth surfaces like glass, with adhesive pressures of 15-30 pounds per square inch for each limb, meaning that a gecko can hang its entire body by one toe. The anatomy of a gecko toe consists of a microscopic hierarchical structure composed of stalk-like setae (100 microns in length, 2 microns in radius). From individual setae, a bundle of hundreds of terminal tips called spatulae (approximately 200 nanometers in diameter at their widest) branch out and contact the climbing surface.

A gecko is able to climb on glass by using physical bond interactions—specifically van der Waals intermolecular forces—between the spatulae and a surface to adhere reversibly, resulting in easy attachment and removal of the gecko’s toes from the surface. The van der Waals mechanism implied that it is the size and shape of the spatulae tips that affect adhesive performance, not specific surface chemistry. This suggested that there were design principles and physical models derived from nature that might enable scientists to fabricate an adhesive inspired by gecko toes.

Humans, of course, have much more weight to carry than a gecko. One of the initial challenges in developing a device to support human climbing was the issue of scaling: a typical Tokay gecko weighs 200 grams, while an average human male weighs 75 kilograms. To enable dynamic climbing like a gecko at this larger scale required that the engineers create climbing paddles capable of balancing sufficient adhesive forces in both the shear (parallel to the vertical surface) and normal (perpendicular to the vertical surface) directions. That feature is necessary for a climber to remain adhered on a surface without falling off while in the act of attaching and detaching the paddles with each movement.

The Draper Laboratory team was also challenged to create novel micro- and nanofabrication technologies to produce the high-aspect-ratio microstructures found in the gecko toe. In the process of achieving that capability, the Z-Man performers transformed the fundamental design and development of reversible adhesives for potential biomedical, industrial, and consumer applications.

The first human climbing demonstration occurred in February 2012 and tests of the technology are ongoing. [emphasis mine]

I’m guessing that glass is difficult to photograph because the image which accompanies the DARPA news release doesn’t highlight the achievement in quite the way one would expect,

During testing, an operator climbed 25 feet vertically on a glass surface using no climbing equipment other than a pair of hand-held, gecko-inspired paddles. The climber wore, but did not require, the use of a safety belay. Image: DARPA

During testing, an operator climbed 25 feet vertically on a glass surface using no climbing equipment other than a pair of hand-held, gecko-inspired paddles. The climber wore, but did not require, the use of a safety belay. Image: DARPA

I last wrote about Z-man in an April 3, 2012 posting highlighting some DARPA-funded work being done at the University of Massachusetts at Amherst while also mentioning work being done in other labs not associated (to my knowledge) with DARPA.

I was not successful in my attempts to find a video highlighting this ‘glass wall’ achievement but I did find this episode of Science Friction, where the host, Rusty Ward, does a very nice job of describing the technology (van der Waals forces, the nanostructures allowing spiders and geckos to climb all sorts of surfaces, etc.) along with some pop culture references (Spider-Man),

This runs for approximately 5 mins. 30 secs., a bit longer than usual for a video embedded here.

One last note, for anyone curious the laboratory referenced in the news release, you can find more here at the (Charles Stark) Draper Laboratory Wikipedia entry.

Staying stuck when it’s wet; learning from the geckos

Researchers from the University of Akron have published another study on geckos and their ‘stickability’ in watery environments. Last mentioned here in my Aug. 10, 2012 posting, doctoral candidate Alyssa Stark  and her colleagues were then testing the geckos by placing them on wetted glass plate surfaces and also by immersing them on water-filled tubs with glass bottom,

Next, the trio sprayed the glass plate with a mist of water and retested the lizards, but this time the animals had problems holding tight: the attachment force varied each time they took a step. The droplets were interfering with the lizards’ attachment mechanism, but it wasn’t clear how. And when the team immersed the geckos in a bath of room temperature water with a smooth glass bottom, the animals were completely unable to anchor themselves to the smooth surface. ‘The toes are superhydrophobic [water repellent]’, explains Stark, who could see a silvery bubble of air around their toes, but they were unable to displace the water surrounding their feet to make the tight van der Waals contacts that usually keep the geckos in place.

Then, the team tested the lizard’s adhesive forces on the dry surface when their feet had been soaking for 90 min and found that the lizards could barely hold on, detaching when they were pulled with a force roughly equalling their own weight. ‘That might be the sliding behaviour that we see when the geckos climb vertically up misted glass’, says Stark. So, geckos climbing on wet surfaces with damp feet are constantly on the verge of slipping and Stark adds that when the soggy lizards were faced with the misted and immersed horizontal surfaces, they slipped as soon as the rig started pulling.

In this latest research, from the Ap. 1, 2013 news release issued by the University of Akron on EurekAlert, Stark and her colleagues announce they’ve discovered the conditions under which geckos can adhere to wet surfaces,

Principal investigator Stark and her fellow UA researchers Ila Badge, Nicholas Wucinich, Timothy Sullivan, Peter Niewiarowski and Ali Dhinojwala study the adhesive qualities of gecko pads, which have tiny, clingy hairs that stick like Velcro to dry surfaces. In a 2012 study, the team discovered that geckos lose their grip on wet glass. This finding led the scientists to explore how the lizards function in their natural environments.

The scientists studied the clinging power of six geckos, which they outfitted with harnesses and tugged upon gently as the lizards clung to surfaces in wet and dry conditions. The researchers found that the effect of water on adhesive strength correlates with wettability, or the ability of a liquid to maintain contact with a solid surface. On glass, which has high wettability, a film of water forms between the surface and the gecko’s foot, decreasing adhesion. Conversely, on surfaces with low wettability, such as waxy leaves on tropical plants, the areas in contact with the gecko’s toes remain dry and adhesion, firm. [emphasis mine]

“The geckos stuck just as well under water as they did on a dry surface, as long as the surface was hydrophobic,” Stark explains. “We believe this is how geckos stick to wet leaves and tree trunks in their natural environment.”

For interested parties, this is where the paper can be found,

The discovery, “Surface Wettability Plays a Significant Role in Gecko Adhesion Underwater,” was published April 1, 2013 by the Proceedings of the National Academy of Sciences. The study has implications for the design of a synthetic gecko-inspired adhesive.

Here’s an image of a gecko (from the University of Akron’s webpage with their Ap. 1, 2013 news release),

Courtesy University of Akron [downloaded from http://www.uakron.edu/im/online-newsroom/news_details.dot?newsId=ec9fd559-e4af-487f-a9cc-2ea5f5c9612d&pageTitle=Top%20Story%20Headline&crumbTitle=Geckos%20keep%20firm%20grip%20in%20wet%20natural%20habitat]

Courtesy University of Akron [downloaded from http://www.uakron.edu/im/online-newsroom/news_details.dot?newsId=ec9fd559-e4af-487f-a9cc-2ea5f5c9612d&pageTitle=Top%20Story%20Headline&crumbTitle=Geckos%20keep%20firm%20grip%20in%20wet%20natural%20habitat]


Not mentioned in this news release, one of the relevant applications for this work would be getting bandages and dressings  to adhere to wet surfaces.

How do you make a harness for a gecko?

It’s the first question (how do you make a harness for a gecko?) I had on reading the latest research about geckos and their ability to adhere to various surfaces, dry and wet. From the Aug. 9,2012 news item on Nanowerk,

But first they had to find out how well their geckos clung onto glass with dry feet. Fitting a tiny harness around the lizard’s pelvis and gently lowering the animal onto a plate of smooth glass, Stark [Alyssa Stark] and Sullivan [Timothy Sullivan] allowed the animal to become well attached before connecting the harness to a tiny motor and gently pull the lizard until it came unstuck. [emphasis mine] The geckos hung on tenaciously, and only came unstuck at forces of around 20N, which is about 20 times their own body weight. ‘The gecko attachment system is over-designed’, says Stark.

Here’s more about the research and the geckos (from the news item),

Geckos are remarkable little creatures, clinging to almost any dry surface, and Alyssa Stark, from the University of Akron, USA, explains that they appear to be equally happy scampering through tropical rainforest canopies as they are in urban settings. ‘A lot of work is done on geckos that looks at the very small adhesive structures on their toes to really understand how the system works at the most basic level’, says Stark. She adds that the animals grip surfaces with microscopic hairs on the soles of their feet that make close enough contact to be attracted to the surface by the minute van der Waals forces between atoms. However, she and her colleagues Timothy Sullivan and Peter Niewiarowski were curious about how the lizards cope on surfaces in their natural habitat.

Explaining that previous studies had focused on the reptiles clinging to artificial dry surfaces, Stark says ‘We know they are in tropical environments that probably have a lot of rain and it’s not like the geckos fall out of the trees when it’s wet’. Yet, the animals do seem to have trouble getting a grip on smooth wet surfaces, sliding down wet vertical glass after a several steps even though minute patches of the animal’s adhesive structures do not slip under humid conditions on moist glass. The team decided to find out how Tokay geckos with wet feet cope on wet and dry surfaces, and publish their discovery that geckos struggle to remain attached as their feet get wetter in The Journal of Experimental Biology (“The effect of surface water and wetting on gecko adhesion” [behind a paywall]).

According to the news item, Tokay geclos were used for this study. These are neither small, nor amiable geckos according to the webpage devoted to Tokay Geckos on the anapsid.org website,

Description
Native to SE Asia, these relatively large (12″) geckos are pale gray with bluish spots when they have been in the dark, darkening to dark gray with reddish spots in the light. Like most geckos, tokays are oviparous insectivores.

Young are 2-3″ at hatching. Eggs are laid in rocky crevices or under the eaves of houses. The 2-3 eggs, laid several times a year, are sticky and adhere to surfaces. In captivity, they may be laid on the glass sides of their terraria. Incubation time for the eggs ranges from 2-6 months for the oviparous Gekko species.

Tokays have the specialized lamellae on the pads of their toes which enable them to walk on vertical surfaces, including ceilings. Contrary to popular misconception, these pads are not “sticky” but rather are composed of tiny, microscopic filaments which find equally tiny imperfections in surface – including glass.

Like many lizards, tokays can darken or lighten their ground and spot colors to better blend in with their background.

Personality
Despite the fact that they follow human habitation, finding human dwellings to be great places to find prey, Tokays are the least lovable of the geckos. They are known for their nasty temperament, cheerfully biting the hand that feeds, cleans or otherwise comes into anything resembling close proximity to them. Their bites are powerful–one might say they are the pit bulls of the gecko world…they hang on and let go only when it suits them. Equipped as they are with numerous sharp teeth, the bites can bleed profusely and, even barring subsequent infection, are annoying for days. Note that while I am a strong believer that almost any animal can be habituated to human contact, such contact can be stressful for many species, and geckos as a whole are known for their marked preference to be left alone.

That harness question gets a lot more interesting after you’ve read about the Tokay Geckos, yes? I found the parts about being “the least lovable of the geckos’ and being known for their nasty bites particularly interesting.

Kathryn Knight’s article about the study for the Journal of Experimental Biology (which originated the news item) offers details about the testing on wet surfaces  (but no more about the harnesses),

Next, the trio sprayed the glass plate with a mist of water and retested the lizards, but this time the animals had problems holding tight: the attachment force varied each time they took a step. The droplets were interfering with the lizards’ attachment mechanism, but it wasn’t clear how. And when the team immersed the geckos in a bath of room temperature water with a smooth glass bottom, the animals were completely unable to anchor themselves to the smooth surface. ‘The toes are superhydrophobic [water repellent]’, explains Stark, who could see a silvery bubble of air around their toes, but they were unable to displace the water surrounding their feet to make the tight van der Waals contacts that usually keep the geckos in place.

Then, the team tested the lizard’s adhesive forces on the dry surface when their feet had been soaking for 90 min and found that the lizards could barely hold on, detaching when they were pulled with a force roughly equalling their own weight. ‘That might be the sliding behaviour that we see when the geckos climb vertically up misted glass’, says Stark. So, geckos climbing on wet surfaces with damp feet are constantly on the verge of slipping and Stark adds that when the soggy lizards were faced with the misted and immersed horizontal surfaces, they slipped as soon as the rig started pulling.

Therefore geckos can walk on wet surfaces, so long as their feet are reasonably dry. However, as soon as their feet get wet, they are barely able to hang on and the team is keen to understand how long it takes geckos to recover from a drenching.

Given the number of studies using geckos, I wonder if there are specialists devoted to creating gecko harnesses. In any case, one certainly can appreciate that the practice of science can sometimes be a blood sport. I think the question being asked is intriguing and it’s the first time I’ve seen any study of the gecko’s adhesive qualities being tested on wet surfaces.