Category Archives: biomimcry

A snout weevil at the end of the rainbow

I’ve never heard of a snout weevil before but it seems to be a marvelous creature,

Caption: Left: A photograph of the ‘rainbow’ weevil, with the rainbow-colored spots on its thorax and elytra (wing casings). Right: A microscope image of the rim of a single rainbow spot, showing the different colors of individual scales. Credit: Dr Bodo D Wilts

From a Sept. 11, 2018 news item on Nanowerk,

Researchers from Yale [University]-NUS College and the University of Fribourg in Switzerland have discovered a novel colour-generation mechanism in nature, which if harnessed, has the potential to create cosmetics and paints with purer and more vivid hues, screen displays that project the same true image when viewed from any angle, and even reduce the signal loss in optical fibres.

Yale-NUS College Assistant Professor of Science (Life Science) Vinodkumar Saranathan led the study with Dr Bodo D Wilts from the Adolphe Merkle Institute at the University of Fribourg. Dr Saranathan examined the rainbow-coloured patterns in the elytra (wing casings) of a snout weevil from the Philippines, Pachyrrhynchus congestus pavonius, using high-energy X-rays, while Dr Wilts performed detailed scanning electron microscopy and optical modelling.

They discovered that to produce the rainbow palette of colours, the weevil utilised a colour-generation mechanism that is so far found only in squid, cuttlefish, and octopuses, which are renowned for their colour-shifting camouflage.

A Sept. 11, 2018 Yale-NUS College news release (also on EurekAlert), which originated the news item, offers more on the weevil and on the research,

P. c. pavonius, or the “Rainbow” Weevil, is distinctive for its rainbow-coloured spots on its thorax and elytra (see attached image). These spots are made up of nearly-circular scales arranged in concentric rings of different hues, ranging from blue in the centre to red at the outside, just like a rainbow. While many insects have the ability to produce one or two colours, it is rare that a single insect can produce such a vast spectrum of colours. Researchers are interested to figure out the mechanism behind the natural formation of these colour-generating structures, as current technology is unable to synthesise structures of this size.

“The ultimate aim of research in this field is to figure out how the weevil self-assembles these structures, because with our current technology we are unable to do so,” Dr Saranathan said. “The ability to produce these structures, which are able to provide a high colour fidelity regardless of the angle you view it from, will have applications in any industry which deals with colour production. We can use these structures in cosmetics and other pigmentations to ensure high-fidelity hues, or in digital displays in your phone or tablet which will allow you to view it from any angle and see the same true image without any colour distortion. We can even use them to make reflective cladding for optical fibres to minimise signal loss during transmission.”

Dr Saranathan and Dr Wilts examined these scales to determine that the scales were composed of a three-dimensional crystalline structure made from chitin (the main ingredient in insect exoskeletons). They discovered that the vibrant rainbow colours on this weevil’s scales are determined by two factors: the size of the crystal structure which makes up each scale, as well as the volume of chitin used to make up the crystal structure. Larger scales have a larger crystalline structure and use a larger volume of chitin to reflect red light; smaller scales have a smaller crystalline structure and use a smaller volume of chitin to reflect blue light. According to Dr Saranathan, who previously examined over 100 species of insects and spiders and catalogued their colour-generation mechanisms, this ability to simultaneously control both size and volume factors to fine-tune the colour produced has never before been shown in insects, and given its complexity, is quite remarkable. “It is different from the usual strategy employed by nature to produce various different hues on the same animal, where the chitin structures are of fixed size and volume, and different colours are generated by orienting the structure at different angles, which reflects different wavelengths of light,” Dr Saranathan explained.

The research was partly supported though the National Centre of Competence in Research “Bio-Inspired Materials” and the Ambizione program of the Swiss National Science Foundation (SNSF) to Dr Wilts, and partly through a UK Royal Society Newton Fellowship, a Linacre College EPA Cephalosporin Junior Research Fellowship, and Yale-NUS College funds to Dr Saranathan. Dr Saranathan is currently part of a research team led by Yale-NUS College Associate Professor of Science Antonia Monteiro, which has recently been awarded a separate Competitive Research Programme (CRP) grant by Singapore’s National Research Foundation (NRF) to examine the genetic basis of the colour-generation mechanism in butterflies. Dr Saranathan and Dr Monteiro are both also from the Department of Biological Sciences at the National University of Singapore (NUS) Faculty of Science. In addition, Dr Saranathan is affiliated with the NUS Nanoscience and Nanotechnology Initiative.

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

Literal Elytral Rainbow: Tunable Structural Colors Using Single Diamond Biophotonic Crystals in Pachyrrhynchus congestus Weevils by Bodo D. Wilts, Vinodkumar Saranathan. Samll https://doi.org/10.1002/smll.201802328 First published: 15 August 2018

This paper is behind a paywall.

Iridescent giant clams could point the way to safety, climatologically speaking

Giant clams in Palau (Cynthia Barnett)

These don’t look like any clams I’ve ever seen but that is the point of Cynthia Barnett’s absorbing Sept. 10, 2018 article for The Atlantic (Note: A link has been removed),

Snorkeling amid the tree-tangled rock islands of Ngermid Bay in the western Pacific nation of Palau, Alison Sweeney lingers at a plunging coral ledge, photographing every giant clam she sees along a 50-meter transect. In Palau, as in few other places in the world, this means she is going to be underwater for a skin-wrinkling long time.

At least the clams are making it easy for Sweeney, a biophysicist at the University of Pennsylvania. The animals plump from their shells like painted lips, shimmering in blues, purples, greens, golds, and even electric browns. The largest are a foot across and radiate from the sea floor, but most are the smallest of the giant clams, five-inch Tridacna crocea, living higher up on the reef. Their fleshy Technicolor smiles beam in all directions from the corals and rocks of Ngermid Bay.

… Some of the corals are bleached from the conditions in Ngermid Bay, where naturally high temperatures and acidity mirror the expected effects of climate change on the global oceans. (Ngermid Bay is more commonly known as “Nikko Bay,” but traditional leaders and government officials are working to revive the indigenous name of Ngermid.)

Even those clams living on bleached corals are pulsing color, like wildflowers in a white-hot desert. Sweeney’s ponytail flows out behind her as she nears them with her camera. They startle back into their fluted shells. Like bashful fairytale creatures cursed with irresistible beauty, they cannot help but draw attention with their sparkly glow.

Barnett makes them seem magical and perhaps they are (Note: A link has been removed),

It’s the glow that drew Sweeney’s attention to giant clams, and to Palau, a tiny republic of more than 300 islands between the Philippines and Guam. Its sun-laden waters are home to seven of the world’s dozen giant-clam species, from the storied Tridacna gigas—which can weigh an estimated 550 pounds and measure over four feet across—to the elegantly fluted Tridacna squamosa. Sweeney first came to the archipelago in 2009, while working on animal iridescence as a post-doctoral fellow at the University of California at Santa Barbara. Whether shimmering from a blue morpho butterfly’s wings or a squid’s skin, iridescence is almost always associated with a visual signal—one used to attract mates or confuse predators. Giant clams’ luminosity is not such a signal. So, what is it?

In the years since, Sweeney and her colleagues have discovered that the clams’ iridescence is essentially the outer glow of a solar transformer—optimized over millions of years to run on sunlight and algal biofuel. Giant clams reach their cartoonish proportions thanks to an exceptional ability to grow their own photosynthetic algae in vertical farms spread throughout their flesh. Sweeney and other scientists think this evolved expertise may shed light on alternative fuel technologies and other industrial solutions for a warming world.

Barnett goes on to describe Palau’s relationship to the clams and the clams’ environment,

Palau’s islands have been inhabited for at least 3,400 years, and from the start, giant clams were a staple of diet, daily life, and even deity. Many of the islands’ oldest-surviving tools are crafted of thick giant-clam shell: arched-blade adzes, fishhooks, gougers, heavy taro-root pounders. Giant-clam shell makes up more than three-fourths of some of the oldest shell middens in Palau, a percentage that decreases through the centuries. Archaeologists suggest that the earliest islanders depleted the giant clams that crowded the crystalline shallows, then may have self-corrected. Ancient Palauan conservation law, known as bul, prohibited fishing during critical spawning periods, or when a species showed signs of over-harvesting.

Before the Christianity that now dominates Palauan religion sailed in on eighteenth-century mission ships, the culture’s creation lore began with a giant clam called to life in an empty sea. The clam grew bigger and bigger until it sired Latmikaik, the mother of human children, who birthed them with the help of storms and ocean currents.

The legend evokes giant clams in their larval phase, moving with the currents for their first two weeks of life. Before they can settle, the swimming larvae must find and ingest one or two photosynthetic alga, which later multiply, becoming self-replicating fuel cells. After the larvae down the alga and develop a wee shell and a foot, they kick around like undersea farmers, looking for a sunny spot for their crop. When they’ve chosen a well-lit home in a shallow lagoon or reef, they affix to the rock, their shell gaping to the sky. After the sun hits and photosynthesis begins, the microalgae will multiply to millions, or in the case of T. gigas, billions, and clam and algae will live in symbiosis for life.

Giant clam is a beloved staple in Palau and many other Pacific islands, prepared raw with lemon, simmered into coconut soup, baked into a savory pancake, or sliced and sautéed in a dozen other ways. But luxury demand for their ivory-like shells and their adductor muscle, which is coveted as high-end sashimi and an alleged aphrodisiac, has driven T. gigas extinct in China, Taiwan, and other parts of their native habitat. Some of the toughest marine-protection laws in the world, along with giant-clam aquaculture pioneered here, have helped Palau’s wild clams survive. The Palau Mariculture Demonstration Center raises hundreds of thousands of giant clams a year, supplying local clam farmers who sell to restaurants and the aquarium trade and keeping pressure off the wild population. But as other nations have wiped out their clams, Palau’s 230,000-square-mile ocean territory is an increasing target of illegal foreign fishers.

Barnett delves into how the country of Palau is responding to the voracious appetite for the giant clams and other marine life,

Palau, drawing on its ancient conservation tradition of bul, is fighting back. In 2015, President Tommy Remengesau Jr. signed into law the Palau National Marine Sanctuary Act, which prohibits fishing in 80 percent of Palau’s Exclusive Economic Zone and creates a domestic fishing area in the remaining 20 percent, set aside for local fishers selling to local markets. In 2016, the nation received a $6.6 million grant from Japan to launch a major renovation of the Palau Mariculture Demonstration Center. Now under construction at the waterfront on the southern tip of Malakal Island, the new facility will amp up clam-aquaculture research and increase giant-clam production five-fold, to more than a million seedlings a year.

Last year, Palau amended its immigration policy to require that all visitors sign a pledge to behave in an ecologically responsible manner. The pledge, stamped into passports by an immigration officer who watches you sign, is written to the island’s children:

Children of Palau, I take this pledge, as your guest, to preserve and protect your beautiful and unique island home. I vow to tread lightly, act kindly and explore mindfully. I shall not take what is not given. I shall not harm what does not harm me. The only footprints I shall leave are those that will wash away.

The pledge is winning hearts and public-relations awards. But Palau’s existential challenge is still the collective “we,” the world’s rising carbon emissions and the resulting upturns in global temperatures, sea levels, and destructive storms.

F. Umiich Sengebau, Palau’s Minister for Natural Resources, Environment, and Tourism, grew up on Koror and is full of giant-clam proverbs, wisdom and legends from his youth. He tells me a story I also heard from an elder in the state of Airai: that in old times, giant clams were known as “stormy-weather food,” the fresh staple that was easy to collect and have on hand when it was too stormy to go out fishing.

As Palau faces the storms of climate change, Sengebau sees giant clams becoming another sort of stormy-weather food, serving as a secure source of protein; a fishing livelihood; a glowing icon for tourists; and now, an inspiration for alternative energy and other low-carbon technologies. “In the old days, clams saved us,” Sengebau tells me. “I think there’s a lot of power in that, a great power and meaning in the history of clams as food, and now clams as science.”

I highly recommend Barnett’s article, which is one article in a larger series, from a November 6, 2017 The Atlantic press release,

The Atlantic is expanding the global footprint of its science writing today with a multi-year series to investigate life in all of its multitudes. The series, “Life Up Close,” created with support from Howard Hughes Medical Institute’s Department of Science Education (HHMI), begins today at TheAtlantic.com. In the first piece for the project, “The Zombie Diseases of Climate Change,” The Atlantic’s Robinson Meyer travels to Greenland to report on the potentially dangerous microbes emerging from thawing Arctic permafrost.

The project is ambitious in both scope and geographic reach, and will explore how life is adapting to our changing planet. Journalists will travel the globe to examine these changes as they happen to microbes, plants, and animals in oceans, grasslands, forests, deserts, and the icy poles. The Atlantic will question where humans should look for life next: from the Martian subsurface, to Europa’s oceans, to the atmosphere of nearby stars and beyond. “Life Up Close” will feature at least twenty reported pieces continuing through 2018.

“The Atlantic has been around for 160 years, but that’s a mere pinpoint in history when it comes to questions of life and where it started, and where we’re going,” said Ross Andersen, The Atlantic’s senior editor who oversees science, tech, and health. “The questions that this project will set out to tackle are critical; and this support will allow us to cover new territory in new and more ambitious ways.”

About The Atlantic:
Founded in 1857 and today one of the fastest growing media platforms in the industry, The Atlantic has throughout its history championed the power of big ideas and continues to shape global debate across print, digital, events, and video platforms. With its award-winning digital presence TheAtlantic.com and CityLab.com on cities around the world, The Atlantic is a multimedia forum on the most critical issues of our times—from politics, business, urban affairs, and the economy, to technology, arts, and culture. The Atlantic is celebrating its 160th anniversary this year. Bob Cohn is president of The Atlantic and Jeffrey Goldberg is editor in chief.

About the Howard Hughes Medical Institute (HHMI) Department of Science Education:
HHMI is the leading private nonprofit supporter of scientific research and science education in the United States. The Department of Science Education’s BioInteractive division produces free, high quality educational media for science educators and millions of students around the globe, its HHMI Tangled Bank Studios unit crafts powerful stories of scientific discovery for television and big screens, and its grants program aims to transform science education in universities and colleges. For more information, visit www.hhmi.org.

Getting back to the giant clams, sometimes all you can do is marvel, eh?

A solar, self-charging supercapacitor for wearable technology

Ravinder Dahiya, Carlos García Núñez, and their colleagues at the University of Glasgow (Scotland) strike again (see my May 10, 2017 posting for their first ‘solar-powered graphene skin’ research announcement). Last time it was all about robots and prosthetics, this time they’ve focused on wearable technology according to a July 18, 2018 news item on phys.org,

A new form of solar-powered supercapacitor could help make future wearable technologies lighter and more energy-efficient, scientists say.

In a paper published in the journal Nano Energy, researchers from the University of Glasgow’s Bendable Electronics and Sensing Technologies (BEST) group describe how they have developed a promising new type of graphene supercapacitor, which could be used in the next generation of wearable health sensors.

A July 18, 2018 University of Glasgow press release, which originated the news item, explains further,

Currently, wearable systems generally rely on relatively heavy, inflexible batteries, which can be uncomfortable for long-term users. The BEST team, led by Professor Ravinder Dahiya, have built on their previous success in developing flexible sensors by developing a supercapacitor which could power health sensors capable of conforming to wearer’s bodies, offering more comfort and a more consistent contact with skin to better collect health data.

Their new supercapacitor uses layers of flexible, three-dimensional porous foam formed from graphene and silver to produce a device capable of storing and releasing around three times more power than any similar flexible supercapacitor. The team demonstrated the durability of the supercapacitor, showing that it provided power consistently across 25,000 charging and discharging cycles.

They have also found a way to charge the system by integrating it with flexible solar powered skin already developed by the BEST group, effectively creating an entirely self-charging system, as well as a pH sensor which uses wearer’s sweat to monitor their health.

Professor Dahiya said: “We’re very pleased by the progress this new form of solar-powered supercapacitor represents. A flexible, wearable health monitoring system which only requires exposure to sunlight to charge has a lot of obvious commercial appeal, but the underlying technology has a great deal of additional potential.

“This research could take the wearable systems for health monitoring to remote parts of the world where solar power is often the most reliable source of energy, and it could also increase the efficiency of hybrid electric vehicles. We’re already looking at further integrating the technology into flexible synthetic skin which we’re developing for use in advanced prosthetics.” [emphasis mine]

In addition to the team’s work on robots, prosthetics, and graphene ‘skin’ mentioned in the May 10, 2017 posting the team is working on a synthetic ‘brainy’ skin for which they have just received £1.5m funding from the Engineering and Physical Science Research Council (EPSRC).

Brainy skin

A July 3, 2018 University of Glasgow press release discusses the proposed work in more detail,

A robotic hand covered in ‘brainy skin’ that mimics the human sense of touch is being developed by scientists.

University of Glasgow’s Professor Ravinder Dahiya has plans to develop ultra-flexible, synthetic Brainy Skin that ‘thinks for itself’.

The super-flexible, hypersensitive skin may one day be used to make more responsive prosthetics for amputees, or to build robots with a sense of touch.

Brainy Skin reacts like human skin, which has its own neurons that respond immediately to touch rather than having to relay the whole message to the brain.

This electronic ‘thinking skin’ is made from silicon based printed neural transistors and graphene – an ultra-thin form of carbon that is only an atom thick, but stronger than steel.

The new version is more powerful, less cumbersome and would work better than earlier prototypes, also developed by Professor Dahiya and his Bendable Electronics and Sensing Technologies (BEST) team at the University’s School of Engineering.

His futuristic research, called neuPRINTSKIN (Neuromorphic Printed Tactile Skin), has just received another £1.5m funding from the Engineering and Physical Science Research Council (EPSRC).

Professor Dahiya said: “Human skin is an incredibly complex system capable of detecting pressure, temperature and texture through an array of neural sensors that carry signals from the skin to the brain.

“Inspired by real skin, this project will harness the technological advances in electronic engineering to mimic some features of human skin, such as softness, bendability and now, also sense of touch. This skin will not just mimic the morphology of the skin but also its functionality.

“Brainy Skin is critical for the autonomy of robots and for a safe human-robot interaction to meet emerging societal needs such as helping the elderly.”

Synthetic ‘Brainy Skin’ with sense of touch gets £1.5m funding. Photo of Professor Ravinder Dahiya

This latest advance means tactile data is gathered over large areas by the synthetic skin’s computing system rather than sent to the brain for interpretation.

With additional EPSRC funding, which extends Professor Dahiya’s fellowship by another three years, he plans to introduce tactile skin with neuron-like processing. This breakthrough in the tactile sensing research will lead to the first neuromorphic tactile skin, or ‘brainy skin.’

To achieve this, Professor Dahiya will add a new neural layer to the e-skin that he has already developed using printing silicon nanowires.

Professor Dahiya added: “By adding a neural layer underneath the current tactile skin, neuPRINTSKIN will add significant new perspective to the e-skin research, and trigger transformations in several areas such as robotics, prosthetics, artificial intelligence, wearable systems, next-generation computing, and flexible and printed electronics.”

The Engineering and Physical Sciences Research Council (EPSRC) is part of UK Research and Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.

EPSRC is the main funding body for engineering and physical sciences research in the UK. By investing in research and postgraduate training, the EPSRC is building the knowledge and skills base needed to address the scientific and technological challenges facing the nation.

Its portfolio covers a vast range of fields from healthcare technologies to structural engineering, manufacturing to mathematics, advanced materials to chemistry. The research funded by EPSRC has impact across all sectors. It provides a platform for future UK prosperity by contributing to a healthy, connected, resilient, productive nation.

It’s fascinating to note how these pieces of research fit together for wearable technology and health monitoring and creating more responsive robot ‘skin’ and, possibly, prosthetic devices that would allow someone to feel again.

The latest research paper

Getting back the solar-charging supercapacitors mentioned in the opening, here’s a link to and a citation for the team’s latest research paper,

Flexible self-charging supercapacitor based on graphene-Ag-3D graphene foam electrodes by Libu Manjakka, Carlos García Núñez, Wenting Dang, Ravinder Dahiya. Nano Energy Volume 51, September 2018, Pages 604-612 DOI: https://doi.org/10.1016/j.nanoen.2018.06.072

This paper is open access.

Moths with sound absorption stealth technology

The cabbage tree emperor moth (Thomas Neil) [downloaded from https://www.cbc.ca/radio/quirks/nov-17-2018-greenland-asteroid-impact-short-people-in-the-rain-forest-reef-islands-and-sea-level-and-more-1.4906857/how-moths-evolved-a-kind-of-stealth-jet-technology-to-sneak-past-bats-1.4906866]

I don’t think I’ve ever seen a more gorgeous moth and it seems a perfect way to enter 2019, from a November 16, 2018 news item on CBC (Canadian Broadcasting Corporation),

A species of silk moth has evolved special sound absorbing scales on its wings to absorb the sonar pulses from hunting bats. This is analogous to the special coatings on stealth aircraft that allow them to be nearly invisible to radar.

“It’s a battle out there every night, insects flying for their lives trying to avoid becoming a bat’s next dinner,” said Dr. Marc Holderied, the senior author on the paper and an associate professor in the School of Biological Sciences at the University of Bristol.

“If you manage to absorb some of these sound energies, it would make you look smaller and let you be detectable over a shorter distance because echoe isn’t strong enough outside the detection bubble.”

Many moths have ears that warn them when a bat is nearby. But not the big and juicy cabbage tree emperor moths which would ordinarily make the perfect meal for bats.

The researchers prepared a brief animated feature illustrating the research,

Prior to publication of the study, the scientists made a presentation at the Acoustical Society of America’s 176th Meeting, held in conjunction with the Canadian Acoustical Association’s 2018 Acoustics Week, Nov. 5-9 at the Victoria Conference Centre in Victoria, Canada according to a November 7, 2018 University of Bristol press release (also on EurekAlert but submitted by the Acoustical Society of America on November 6, 2018),

Moths are a mainstay food source for bats, which use echolocation (biological sonar) to hunt their prey. Scientists such as Thomas Neil, from the University of Bristol in the U.K., are studying how moths have evolved passive defenses over millions of years to resist their primary predators.

While some moths have evolved ears that detect the ultrasonic calls of bats, many types of moths remain deaf. In those moths, Neil has found that the insects developed types of “stealth coating” that serve as acoustic camouflage to evade hungry bats.

Neil will describe his work during the Acoustical Society of America’s 176th Meeting, held in conjunction with the Canadian Acoustical Association’s 2018 Acoustics Week, Nov. 5-9 at the Victoria Conference Centre in Victoria, Canada.

In his presentation, Neil will focus on how fur on a moth’s thorax and wing joints provide acoustic stealth by reducing the echoes of these body parts from bat calls.

“Thoracic fur provides substantial acoustic stealth at all ecologically relevant ultrasonic frequencies,” said Neil, a researcher at Bristol University. “The thorax fur of moths acts as a lightweight porous sound absorber, facilitating acoustic camouflage and offering a significant survival advantage against bats.” Removing the fur from the moth’s thorax increased its detection risk by as much as 38 percent.

Neil used acoustic tomography to quantify echo strength in the spatial and frequency domains of two deaf moth species that are subject to bat predation and two butterfly species that are not.

In comparing the effects of removing thorax fur from insects that serve as food for bats to those that don’t, Neil’s research team found that thoracic fur determines acoustic camouflage of moths but not butterflies.

“We found that the fur on moths was both thicker and denser than that of the butterflies, and these parameters seem to be linked with the absorptive performance of their respective furs,” Neil said. “The thorax fur of the moths was able to absorb up to 85 percent of the impinging sound energy. The maximum absorption we found in butterflies was just 20 percent.”

Neil’s research could contribute to the development of biomimetic materials for ultrathin sound absorbers and other noise-control devices.

“Moth fur is thin and lightweight,” said Neil, “and acts as a broadband and multidirectional ultrasound absorber that is on par with the performance of current porous sound-absorbing foams.”

Moth fur? This has changed my view of moths although I reserve the right to get cranky when local moths chew through my wool sweaters. Here’s a link to and a citation for the paper,

Biomechanics of a moth scale at ultrasonic frequencies by Zhiyuan Shen, Thomas R. Neil, Daniel Robert, Bruce W. Drinkwater, and Marc W. Holderied. PNAS [Proccedings of the National Academy of Sciences of the United States of America] November 27, 2018 115 (48) 12200-12205; published ahead of print November 12, 2018 https://doi.org/10.1073/pnas.1810025115

This paper is behind a paywall.

Unusually I’m going to include the paper’s abstract here,

The wings of moths and butterflies are densely covered in scales that exhibit intricate shapes and sculptured nanostructures. While certain butterfly scales create nanoscale photonic effects [emphasis mine], moth scales show different nanostructures suggesting different functionality. Here we investigate moth-scale vibrodynamics to understand their role in creating acoustic camouflage against bat echolocation, where scales on wings provide ultrasound absorber functionality. For this, individual scales can be considered as building blocks with adapted biomechanical properties at ultrasonic frequencies. The 3D nanostructure of a full Bunaea alcinoe moth forewing scale was characterized using confocal microscopy. Structurally, this scale is double layered and endowed with different perforation rates on the upper and lower laminae, which are interconnected by trabeculae pillars. From these observations a parameterized model of the scale’s nanostructure was formed and its effective elastic stiffness matrix extracted. Macroscale numerical modeling of scale vibrodynamics showed close qualitative and quantitative agreement with scanning laser Doppler vibrometry measurement of this scale’s oscillations, suggesting that the governing biomechanics have been captured accurately. Importantly, this scale of B. alcinoe exhibits its first three resonances in the typical echolocation frequency range of bats, suggesting it has evolved as a resonant absorber. Damping coefficients of the moth-scale resonator and ultrasonic absorption of a scaled wing were estimated using numerical modeling. The calculated absorption coefficient of 0.50 agrees with the published maximum acoustic effect of wing scaling. Understanding scale vibroacoustic behavior helps create macroscopic structures with the capacity for broadband acoustic camouflage.

Those nanoscale photonic effects caused by butterfly scales are something I’d usually describe as optical effects due to the nanoscale structures on some butterfly wings, notably those of the Blue Morpho butterfly. In fact there’s a whole field of study on what’s known as structural colo(u)r. Strictly speaking I’m not sure you could describe the nanostructures on Glasswing butterflies as an example of structure colour since those structures make that butterfly’s wings transparent but they are definitely an optical effect. For the curious, you can use ‘blue morpho butterfly’, ‘glasswing butterfly’ or ‘structural colo(u)r’ to search for more on this blog or pursue bigger fish with an internet search.

New semiconductor material from pigment produced by fungi?

Chlorociboria Aeruginascens fungus on a tree log. (Image: Oregon State University)

Apparently the pigment derived from the fungi you see in the above picture is used by visual artists and, perhaps soon, will be used by electronics manufacturers. From a June 5, 2018 news item on Nanowerk,

Researchers at Oregon State University are looking at a highly durable organic pigment, used by humans in artwork for hundreds of years, as a promising possibility as a semiconductor material.

Findings suggest it could become a sustainable, low-cost, easily fabricated alternative to silicon in electronic or optoelectronic applications where the high-performance capabilities of silicon aren’t required.

Optoelectronics is technology working with the combined use of light and electronics, such as solar cells, and the pigment being studied is xylindein.

A June 5, 2018 Oregon State University news release by Steve Lundeberg, which originated the news item, expands on the theme,

“Xylindein is pretty, but can it also be useful? How much can we squeeze out of it?” said Oregon State University [OSU] physicist Oksana Ostroverkhova. “It functions as an electronic material but not a great one, but there’s optimism we can make it better.”

Xylindien is secreted by two wood-eating fungi in the Chlorociboria genus. Any wood that’s infected by the fungi is stained a blue-green color, and artisans have prized xylindein-affected wood for centuries.

The pigment is so stable that decorative products made half a millennium ago still exhibit its distinctive hue. It holds up against prolonged exposure to heat, ultraviolet light and electrical stress.

“If we can learn the secret for why those fungi-produced pigments are so stable, we could solve a problem that exists with organic electronics,” Ostroverkhova said. “Also, many organic electronic materials are too expensive to produce, so we’re looking to do something inexpensively in an ecologically friendly way that’s good for the economy.”

With current fabrication techniques, xylindein tends to form non-uniform films with a porous, irregular, “rocky” structure.

“There’s a lot of performance variation,” she said. “You can tinker with it in the lab, but you can’t really make a technologically relevant device out of it on a large scale. But we found a way to make it more easily processed and to get a decent film quality.”

Ostroverkhova and collaborators in OSU’s colleges of Science and Forestry blended xylindein with a transparent, non-conductive polymer, poly(methyl methacrylate), abbreviated to PMMA and sometimes known as acrylic glass. They drop-cast solutions both of pristine xylindein and a xlyindein-PMMA blend onto electrodes on a glass substrate for testing.

They found the non-conducting polymer greatly improved the film structure without a detrimental effect on xylindein’s electrical properties. And the blended films actually showed better photosensitivity.

“Exactly why that happened, and its potential value in solar cells, is something we’ll be investigating in future research,” Ostroverkhova said. “We’ll also look into replacing the polymer with a natural product – something sustainable made from cellulose. We could grow the pigment from the cellulose and be able to make a device that’s all ready to go.

“Xylindein will never beat silicon, but for many applications, it doesn’t need to beat silicon,” she said. “It could work well for depositing onto large, flexible substrates, like for making wearable electronics.”

This research, whose findings were recently published in MRS Advances, represents the first use of a fungus-produced material in a thin-film electrical device.

“And there are a lot more of the materials,” Ostroverkhova said. “This is just first one we’ve explored. It could be the beginning of a whole new class of organic electronic materials.”

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

Fungi-Derived Pigments for Sustainable Organic (Opto)Electronics by Gregory Giesbers, Jonathan Van Schenck, Sarath Vega Gutierrez, Sara Robinson. MRS Advances https://doi.org/10.1557/adv.2018.446 Published online: 21 May 2018

This paper is behind a paywall.

Spider glue

Caption: An orb spider, glue-maker extraordinaire, at work on a web. Credit: The University of Akron

Scientists are taking inspiration from spiders in their quest to develop better adhesives. (Are they abandoning the gecko? Usually when scientists study adhesiveness, there’s talk of geckos. From a June 5, 2018 news item on ScienceDaily,

Ever wonder why paint peels off the wall during summer’s high humidity? It’s the same reason that bandages separate from skin when we bathe or swim.

Interfacial water, as it’s known, forms a slippery and non-adhesive layer between the glue and the surface to which it is meant to stick, interfering with the formation of adhesive bonds between the two.

Overcoming the effects of interfacial water is one of the challenges facing developers of commercial adhesives.

To find a solution, researchers at The University of Akron (UA) are looking to one of the strongest materials found in nature: spider silk.

The sticky glue that coats the silk threads of spider webs is a hydrogel, meaning it is full of water. One would think, then, that spiders would have difficulty catching prey, especially in humid conditions — but they do not. In fact, their sticky glue, which has been a subject of intensive research for years, is one of the most effective biological glues in all of nature.

A June 4, 2018 University of Akron news release (also on EurekAlert published on June 5, 2018), which originated the news item, provides more detail,

So how is spider glue able to stick in highly humid conditions?

That question was the subject of investigation by UA graduate students Saranshu Singla, Gaurav Amarpuri and Nishad Dhopatkar, who have been working with Dr. Ali Dhinojwala, interim dean of the College of Polymer Science and Polymer Engineering, and Dr. Todd Blackledge, professor of biology in the Integrated Bioscience program. Both professors are principal investigators in UA’s Biomimicry Research Innovation Center [BRIC], which specializes in emulating biological forms, processes, patterns and systems to solve technical challenges.

The team’s findings, which may provide the clue to developing stronger commercial adhesives, can be read in a paper recently published in the journal Nature Communications.

Singla and her colleagues set out to examine the secret behind the success of the common orb spider (Larinioides cornutus) glue and uncover how it overcomes the primary obstacle of achieving good adhesion in the humid conditions where water could be present between the glue and the target surface.

To investigate the processes involved, the team took orb spider glue, set it on sapphire substrate, then examined it using a combination of interface-sensitive spectroscopy and infrared spectroscopy.

Spider glue is made of three elements: two specialized glycoproteins, a collection of low molecular mass organic and inorganic compounds (LMMCs), and water. The LMMCs are hygroscopic (water-attracting), which keeps the glue soft and tacky to stick.

Singla and her team discovered that these glycoproteins act as primary binding agents to the surface. Glycoprotein-based glues have been identified in several other biological glues, such as fungi, algae, diatoms, sea stars, sticklebacks and English ivy.

But why doesn’t the water present in the spider glue interfere with the adhesive contact the way it does with most synthetic adhesives?

The LMMCs, the team concluded, perform a previously unknown function of sequestering interfacial water, preventing adhesive failure.

Singla and colleagues determined that it is the interaction of glycoproteins and LMMCs that governs the adhesive quality of the glue produced, with the respective proportions varying across species, thus optimizing adhesive strength to match the relative humidity of spider habitat.

“The hygroscopic compounds – known as water-absorbers – in spider glue play a previously unknown role in moving water away from the boundary, thereby preventing failure of spider glue at high humidity,” explained Singla.

The ability of the spider glue to overcome the problem of interfacial water by effectively absorbing it is the key finding of the research, and the one with perhaps the strongest prospect for commercial development.

“Imagine a paint that is guaranteed for life, come rain or shine,” Singla remarked.

All thanks to your friendly neighborhood spider glue.

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

Hygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions by Saranshu Singla, Gaurav Amarpuri, Nishad Dhopatkar, Todd A. Blackledge, & Ali Dhinojwala. Nature Communicationsvolume 9, Article number: 1890 (2018) Published 22 May 2018 DOI: https://doi.org/10.1038/s41467-018-04263-z

This paper is open access.

Regenerating dental enamel

For anyone who’s concerned about their dental enamel, this research might prove encouraging. From a June 1, 2018 news item on Nanowerk,

Researchers at Queen Mary University of London [UK][ have developed a new way to grow mineralised materials which could regenerate hard tissues such as dental enamel and bone.

Enamel, located on the outer part of our teeth, is the hardest tissue in the body and enables our teeth to function for a large part of our lifetime despite biting forces, exposure to acidic foods and drinks and extreme temperatures. This remarkable performance results from its highly organised structure.

However, unlike other tissues of the body, enamel cannot regenerate once it is lost, which can lead to pain and tooth loss. These problems affect more than 50 per cent of the world’s population and so finding ways to recreate enamel has long been a major need in dentistry.

A June 1, 2018 Queen Mary University of London press release, which originated the news item, provides more detail,

The study, published in Nature Communications, shows that this new approach can create materials with remarkable precision and order that look and behave like dental enamel.

The materials could be used for a wide variety of dental complications such as the prevention and treatment of tooth decay or tooth sensitivity – also known as dentin hypersensitivity.

Simple and versatile

Dr Sherif Elsharkawy, a dentist and first author of the study from Queen Mary’s School of Engineering and Materials Science, said: “This is exciting because the simplicity and versatility of the mineralisation platform opens up opportunities to treat and regenerate dental tissues. For example, we could develop acid resistant bandages that can infiltrate, mineralise, and shield exposed dentinal tubules of human teeth for the treatment of dentin hypersensitivity.”

The mechanism that has been developed is based on a specific protein material that is able to trigger and guide the growth of apatite nanocrystals at multiple scales – similarly to how these crystals grow when dental enamel develops in our body. This structural organisation is critical for the outstanding physical properties exhibited by natural dental enamel.

Lead author Professor Alvaro Mata, also from Queen Mary’s School of Engineering and Materials Science, said: “A major goal in materials science is to learn from nature to develop useful materials based on the precise control of molecular building-blocks. The key discovery has been the possibility to exploit disordered proteins to control and guide the process of mineralisation at multiple scales. Through this, we have developed a technique to easily grow synthetic materials that emulate such hierarchically organised architecture over large areas and with the capacity to tune their properties.”

Mimic other hard tissues

Enabling control of the mineralisation process opens the possibility to create materials with properties that mimic different hard tissues beyond enamel such as bone and dentin. As such, the work has the potential to be used in a variety of applications in regenerative medicine. In addition, the study also provides insights into the role of protein disorder in human physiology and pathology.

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

Protein disorder–order interplay to guide the growth of hierarchical mineralized structures by Sherif Elsharkawy, Maisoon Al-Jawad, Maria F. Pantano, Esther Tejeda-Montes, Khushbu Mehta, Hasan Jamal, Shweta Agarwal, Kseniya Shuturminska, Alistair Rice, Nadezda V. Tarakina, Rory M. Wilson, Andy J. Bushby, Matilde Alonso, Jose C. Rodriguez-Cabello, Ettore Barbieri, Armando del Río Hernández, Molly M. Stevens, Nicola M. Pugno, Paul Anderson, & Alvaro Mata. Nature Communicationsvolume 9, Article number: 2145 (2018) Published 01 June 2018 DOI: https://doi.org/10.1038/s41467-018-04319-0

This paper is open access.

One final comment, this work is at the ‘in vitro’ stage. More colloquially, this is being done in a petri dish or glass vial or some other container and it’s going to be a long time before there are going to be any human clinical trials, assuming the work gets that far.

Killing bacteria on contact with dragonfly-inspired nanocoating

Scientists in Singapore were inspired by dragonflies and cicadas according to a March 28, 2018 news item on Nanowerk (Note: A link has been removed),

Studies have shown that the wings of dragonflies and cicadas prevent bacterial growth due to their natural structure. The surfaces of their wings are covered in nanopillars making them look like a bed of nails. When bacteria come into contact with these surfaces, their cell membranes get ripped apart immediately and they are killed. This inspired researchers from the Institute of Bioengineering and Nanotechnology (IBN) of A*STAR to invent an anti-bacterial nano coating for disinfecting frequently touched surfaces such as door handles, tables and lift buttons.

This technology will prove particularly useful in creating bacteria-free surfaces in places like hospitals and clinics, where sterilization is important to help control the spread of infections. Their new research was recently published in the journal Small (“ZnO Nanopillar Coated Surfaces with Substrate-Dependent Superbactericidal Property”)

Image 1: Zinc oxide nanopillars that looked like a bed of nails can kill a broad range of germs when used as a coating on frequently-touched surfaces. Courtesy: A*STAR

A March 28, 2018 Agency for Science Technology and Research (A*STAR) press release, which originated the news item, describes the work further,

80% of common infections are spread by hands, according to the B.C. [province of Canada] Centre for Disease Control1. Disinfecting commonly touched surfaces helps to reduce the spread of harmful germs by our hands, but would require manual and repeated disinfection because germs grow rapidly. Current disinfectants may also contain chemicals like triclosan which are not recognized as safe and effective 2, and may lead to bacterial resistance and environmental contamination if used extensively.

“There is an urgent need for a better way to disinfect surfaces without causing bacterial resistance or harm to the environment. This will help us to prevent the transmission of infectious diseases from contact with surfaces,” said IBN Executive Director Professor Jackie Y. Ying.

To tackle this problem, a team of researchers led by IBN Group Leader Dr Yugen Zhang created a novel nano coating that can spontaneously kill bacteria upon contact. Inspired by studies on dragonflies and cicadas, the IBN scientists grew nanopilllars of zinc oxide, a compound known for its anti-bacterial and non-toxic properties. The zinc oxide nanopillars can kill a broad range of germs like E. coli and S. aureus that are commonly transmitted from surface contact.

Tests on ceramic, glass, titanium and zinc surfaces showed that the coating effectively killed up to 99.9% of germs found on the surfaces. As the bacteria are killed mechanically rather than chemically, the use of the nano coating would not contribute to environmental pollution. Also, the bacteria will not be able to develop resistance as they are completely destroyed when their cell walls are pierced by the nanopillars upon contact.

Further studies revealed that the nano coating demonstrated the best bacteria killing power when it is applied on zinc surfaces, compared with other surfaces. This is because the zinc oxide nanopillars catalyzed the release of superoxides (or reactive oxygen species), which could even kill nearby free floating bacteria that were not in direct contact with the surface. This super bacteria killing power from the combination of nanopillars and zinc broadens the scope of applications of the coating beyond hard surfaces.

Subsequently, the researchers studied the effect of placing a piece of zinc that had been coated with zinc oxide nanopillars into water containing E. coli. All the bacteria were killed, suggesting that this material could potentially be used for water purification.

Dr Zhang said, “Our nano coating is designed to disinfect surfaces in a novel yet practical way. This study demonstrated that our coating can effectively kill germs on different types of surfaces, and also in water. We were also able to achieve super bacteria killing power when the coating was used on zinc surfaces because of its dual mechanism of action. We hope to use this technology to create bacteria-free surfaces in a safe, inexpensive and effective manner, especially in places where germs tend to accumulate.”

IBN has recently received a grant from the National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Programme to further develop this coating technology in collaboration with Tan Tock Seng Hospital for commercial application over the next 5 years.

1 B.C. Centre for Disease Control

2 U.S. Food & Drug Administration

(I wasn’t expecting to see a reference to my home province [BC Centre for Disease Control].) Back to the usual, here’s a link to and a citation for the paper,

ZnO Nanopillar Coated Surfaces with Substrate‐Dependent Superbactericidal Property by Guangshun Yi, Yuan Yuan, Xiukai Li, Yugen Zhang. Small https://doi.org/10.1002/smll.201703159 First published: 22 February 2018

This paper is behind a paywall.

One final comment, this research reminds me of research into simulating shark skin because that too has bacteria-killing nanostructures. My latest about the sharkskin research is a Sept, 18, 2014 posting.

A gripping problem: tree frogs lead the way

Courtesy: University of Glasgow

At least once a year, there must be a frog posting here (ETA: July 31, 2018 at 1640 hours: unusually, this is my second ‘frog’ posting in one week; my July 26, 2018 posting concerns a very desperate frog, Romeo). Prior to Romeo, this March 15, 2018 news item on phys.org tickled my fancy,

Scientists researching how tree frogs climb have discovered that a unique combination of adhesion and grip gives them perfect technique.

The new research, led by the University of Glasgow and published today [March 15, 2018] in the Journal of Experimental Biology, could have implications for areas of science such as robotics, as well as the production of climbing equipment and even tyre manufacture.

A March 15, 2018 University of Glasgow press release, which originated the news item, provides a little more detail,

Researchers found that, using their fluid-filled adhesive toe pads, tree frogs are able to grip to surfaces to climb. When surfaces aren’t smooth enough to allow adhesion, researchers found that the frogs relied on their long limbs to grip around objects.

University of Glasgow scientists Iain Hill and Jon Barnes gave the tree frogs a series of narrow and wide cylinders to climb. The research team found that on the narrow cylinders the frogs used their grip and adhesion pads, allowing them to climb the obstacle at speed. Wider cylinders were too large for the frogs to grip, so they could only climb more slowly using their suction adhesive pads.

When the cylinders were coated in sandpaper, preventing adhesion, the frogs could only climb the narrow ones slowly, using their grip. They were not able to climb the wider cylinders covered in sandpaper as they couldn’t use their grip or adhesion.

Dr Barnes said: “I have worked on tree frog research for many years and I find them fascinating. Work on tree frogs has been of interest to industry and other areas of science in the past, since their climbing abilities can offer us insights into the most efficient way to climb and stick to surfaces.

“Climbing robots, for instance, need ways to stick, they could be based either on gecko climbing or tree frog climbing.  This research demonstrates how a good climbing robot would need to combine gripping and adhesion to climb more efficiently.”

The study, “The biomechanics of tree frogs climbing curved surfaces: a gripping problem” is published in the Journal ofExperimental Biology. The work was funded by the Royal Society, London and by grants from the National Natural Science Foundation of China and the Natural Science Foundation of Jiangsu Province.

Here’s a link to and a citation for the paper (I love the pun in the title),

The biomechanics of tree frogs climbing curved surfaces: a gripping problem by Iain D. C. Hill, Benzheng Dong, W. Jon. P. Barnes, Aihong Ji, Thomas Endlein. Journal of Experimental Biology 2018 : jeb.168179 doi: 10.1242/jeb.168179 Published 19 January 2018

This paper is behind a paywall.