Tag Archives: blue morpho butterfly

Enlightening Morpho butterfly

Apparently, the Morpho butterfly (or blue morpho butterfly) could inspire more balanced lighting, from an October 12, 2023 news item on phys.org,

As you watch Morpho butterflies wobble in flight, shimmering in vivid blue color, you’re witnessing an uncommon form of structural color that researchers are only beginning to use in lighting technologies such as optical diffusers. Furthermore, imparting a self-cleaning capability to such diffusers would minimize soiling and staining and maximize practical utility.

Now, in a study recently published in Advanced Optical Materials, researchers at Osaka University have developed a water-repelling nanostructured light diffuser that surpasses the functionality of other common diffusers. This work might help solve common lighting dilemmas in modern technologies.

Caption: Design and diffused light for the anisotropic (left) and isotropic (right) Morpho-type diffusers. It has high optical functionalities and anti-fouling properties, which until now have not been realized in one device. Credit: K.Yamashita, A.Saito

An October 12, 2023 Osaka University press release (also on EurekAlert), which originated the news item, sheds some light on the subject (sorry! I couldn’t resist),

Standard lighting can eventually become tiring because it’s unevenly illuminating. Thus, many display technologies use optical diffusers to make the light output more uniform. However, conventional optical diffusers reduce the light output, don’t work well for all emitted colors, or require special effort to clean. Morpho butterflies are an inspiration for improved optical diffusers. Their randomly arranged multilayer architecture enables structural color: in this case, selective reflection of blue light over a ≥±40° angle from the direction of illumination. The goal of the present work is to use this inspiration from nature to design a simplified optical diffuser that has both high transmittance and wide angular spread, works for a range of colors without dispersion, cleans by a simple water rinse, and can be shaped with standard nanofabrication tools.

“We create two-dimensional nanopatterns—in common transparent polydimethylsiloxane elastomer—of binary height yet random width, and the two surfaces have different structural scales,” explains Kazuma Yamashita, lead author of the study. “Thus, we report an effective optical diffuser for short- and long-wavelength light.”

The researchers tailored the patterns of the diffuser surfaces to optimize the performance for blue and red light, and their self-cleaning properties. The experimentally measured light transmittance was >93% over the entire visible light spectrum, and the light diffusion was substantial and could be controlled into anisotropic shape: 78° in the x-direction and 16° in the y-direction (similar to values calculated by simulations). Furthermore, the surfaces both strongly repelled water in contact angle and self-cleaning experiments.

“Applying protective cover glass layers on either side of the optical diffuser largely maintains the optical properties, yet protects against scratching,” says Akira Saito, senior author. “The glass minimizes the need for careful handling, and indicates our technology’s utility to daylight-harvesting windows.”

This work emphasizes that studying the natural world can provide insights for improved everyday devices; in this case, lighting technologies for visual displays. The fact that the diffuser consists of a cheap material that essentially cleans itself and can be easily shaped with common tools might inspire other researchers to apply the results of this work to electronics and many other fields.

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

Development of a High-Performance, Anti-Fouling Optical Diffuser Inspired by Morpho Butterfly’s Nanostructure by Kazuma Yamashita, Kana Taniguchi, Takuma Hattori, Yuji Kuwahara, Akira Saito. Advanced Opticla Materials DOI: https://doi.org/10.1002/adom.202301086 First published: 26 July 2023

This paper is open access.

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?

Structural colo(u)r from transparent 3D printed nanostructures

Caption: Light hits the 3-D printed nanostructures from below. After it is transmitted through, the viewer sees only green light — the remaining colors are redirected. Credit: Thomas Auzinger [downloaded from http://visualcomputing.ist.ac.at/publications/2018/StructCol/]

An August 17, 2018 news item on ScienceDaily announces the work illustrated by the image above,

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and certain color effects are impossible to achieve. The natural world, however, also exhibits structural coloration, where the microstructure of an object causes various colors to appear. Peacock feathers, for instance, are pigmented brown, but — because of long hollows within the feathers — reflect the gorgeous, iridescent blues and greens we see and admire. Recent advances in technology have made it practical to fabricate the kind of nanostructures that result in structural coloration, and computer scientists from the Institute of Science and Technology Austria (IST Austria) and the King Abdullah University of Science and Technology (KAUST) have now created a computational tool that automatically creates 3D-print templates for nanostructures that correspond to user-defined colors. Their work demonstrates the great potential for structural coloring in industry, and opens up possibilities for non-experts to create their own designs. This project will be presented at this year’s top computer graphics conference, SIGGRAPH 2018, by first author and IST Austria postdoc Thomas Auzinger. This is one of five IST Austria presentations at the conference this year.

SIGGRAPH 2018, now ended, was mentioned in my Aug. 9, 2018 posting.but since this presentation is accompanied by a paper, it rates its own posting. For one more excuse, there’s my fascination with structural colour.

An August 17, 2018 Institute of Science and Technology Austria press release (also on EurekAlert), which originated the news item, delves into the work,

The changing colors of a chameleon and the iridescent blues and greens of the morpho butterfly, among many others in nature, are the result of structural coloration, where nanostructures cause interference effects in light, resulting in a variety of colors when viewed macroscopically. Structural coloration has certain advantages over coloring with pigments (where particular wavelengths are absorbed), but until recently, the limits of technology meant fabricating such nanostructures required highly specialized methods. New “direct laser writing” set-ups, however, cost about as much as a high-quality industrial 3D printer, and allow for printing at the scale of hundreds of nanometers (hundred to thousand time thinner than a human hair), opening up possibilities for scientists to experiment with structural coloration.

So far, scientists have primarily experimented with nanostructures that they had observed in nature, or with simple, regular nanostructural designs (e.g. row after row of pillars). Thomas Auzinger and Bernd Bickel of IST Austria, together with Wolfgang Heidrich of KAUST, however, took an innovative new approach that differs in several key ways. First, they solve the inverse design task: the user enters the color they want to replicate, and then the computer creates a nanostructure pattern that gives that color, rather than attempting to reproduce structures found in nature. Moreover, “our design tool is completely automatic,” says Thomas Auzinger. “No extra effort is required on the part of the user.”

Second, the nanostructures in the template do not follow a particular pattern or have a regular structure; they appear to be randomly composed—a radical break from previous methods, but one with many advantages. “When looking at the template produced by the computer I cannot tell by the structure alone, if I see a pattern for blue or red or green,” explains Auzinger. “But that means the computer is finding solutions that we, as humans, could not. This free-form structure is extremely powerful: it allows for greater flexibility and opens up possibilities for additional coloring effects.” For instance, their design tool can be used to print a square that appears red from one angle, and blue from another (known as directional coloring).

Finally, previous efforts have also stumbled when it came to actual fabrication: the designs were often impossible to print. The new design tool, however, guarantees that the user will end up with a printable template, which makes it extremely useful for the future development of structural coloration in industry. “The design tool can be used to prototype new colors and other tools, as well as to find interesting structures that could be produced industrially,” adds Auzinger. Initial tests of the design tool have already yielded successful results. “It’s amazing to see something composed entirely of clear materials appear colored, simply because of structures invisible to the human eye,” says Bernd Bickel, professor at IST Austria, “we’re eager to experiment with additional materials, to expand the range of effects we can achieve.”

“It’s particularly exciting to witness the growing role of computational tools in fabrication,” concludes Auzinger, “and even more exciting to see the expansion of ‘computer graphics’ to encompass physical as well as virtual images.”

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

Computational Design of Nanostructural Color for Additive Manufacturing by Thomas Auzinger, Wolfgang Heidrich, and Bernd Bickel. ACM Trans. Graph. 37, 4, Article 159 (August 2018). 16 pages. doi.org/10.1145/3197517.3201376

This appears to be open access.

There is also a project page bearing the same title as the paper, Computational Design of Nanostructural Color for Additive Manufacturing.

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.

Noniridescent photonics inspired by tarantulas

Last year, I was quite taken with a structural colour story centering on tarantulas which was featured in my Dec. 7, 2015 posting.

Cobalt Blue Tarantula [downloaded from http://www.tarantulaguide.com/tarantula-pictures/cobalt-blue-tarantula-4/]

Cobalt Blue Tarantula [downloaded from http://www.tarantulaguide.com/tarantula-pictures/cobalt-blue-tarantula-4/]

On Oct. 17, 2016 I was delighted to receive an email with the latest work from the same team who this time around crowdfunded resources to complete their research. Before moving on to the paper, here’s more from the team’s crowdfunder on Experiment was titled “The Development of Non-iridescent Structurally Colored Material Inspired by Tarantula Hairs,”

Many vibrant colors in nature are produced by nanostructures rather than pigments. But their application is limited by iridescence – changing hue and brightness with viewing angles. This project aims to mimic the nanostructures that tarantulas use to produce bright, non-iridescent blue colors to inspire next-generation, energy efficient, wide-angle color displays. Moreover, one day non-iridescent structural colorants may replace costly and toxic pigments and dyes.

What is the context of this research?

We recently discovered that some tarantulas produce vivid blue colors using unique nanostructures not found in other blue organisms like birds and Morpho butterflies. We described a number of different nanostructures that help explain how blue color evolved at least eight times within tarantulas. These colors are also remarkably non-iridescent so that they stay bright blue even at wide viewing angles, unlike the “flashy” structural colors seen in many birds and butterflies. We hypothesize that although the hue is produced by multilayer nanostructure, it is the hierarchical morphology of the hairs controls iridescence. We would like to validate our results from preliminary optical simulations by making nano-3D printed physical prototypes with and without key features of the tarantula hairs.

What is the significance of this project?

While iridescence can make a flashy signal to a mating bird or butterfly, it isn’t so useful in optical technology. This limits the application of structural colors in human contexts, even though they can be more vibrant and resist fading better than traditional pigment-based colors. For example, despite being energy efficient and viewable in direct sunlight, this butterfly-inspired color display, that utilizes principles of structural colors, has never made it into the mainstream because iridescence limits its viewing angle. We believe this limitation could be overcome using tarantula-inspired nanostructures that could be mass-produced in an economically viable way through top-down approaches. Those nanostructures may even be used to replace pigments and dyes someday!

What are the goals of the project?

We have designed five models that vary in complexity, incorporating successively more details of real tarantula hairs. We would like to fabricate those five designs by 3D nano-printing, so that we can test our hypothesis experimentally and determine which features produce blue and which remove iridescence. We’ll start making those designs as soon as we reach our goal and the project is fully funded. Once these designs are made, we will compare the angle-dependency of the colors produced by each design through angle-resolved reflectance spectrometry. We’ll also compare them visually through photography by taking series of shots from different angles similar to Fig. S4. Through those steps, we’ll be able to identify how each feature of the complex nanostructure contributes to color.

Budget
Ultra-high resolution (nano-scale) 3D printing
$6,000
To fund nano 3D printing completely
$1,700

This project has been designed using Biomimicry Thinking, and is a follow-up to our published, well-received tarantula research. In order to test our hypothesis, we are planning to use Photonic Professional GT by nanoscribe to fabricate tarantula hair-inspired prototypes by 3D printing nanostructures within millimeter sized swatches. To be able to 3D print nanostructures across these relatively large-sized swatches is critical to the success of our project. Currently, there’s no widely-accessible technology out there that meets our needs other than Photonic Professional GT. However, the estimated cost just for 3D printing those nanostructures alone is $20,000. So far, we have successfully raised and allocated $13,000 of research funds through conventional means, but we are still $7,000 short. Initial trial of our most complex prototype was a success. Therefore, we’re here, seeking your help. Please help us make this nano fabrication happen, and make this project a success! Thank you!

The researchers managed to raise $7, 708.00 in total, making this paper possible,

Tarantula-Inspired Noniridescent Photonics with Long-Range Order by Bor-Kai Hsiung, Radwanul Hasan Siddique, Lijia Jiang, Ying Liu, Yongfeng Lu, Matthew D. Shawkey, and Todd A. Blackledge. Advanced Materials DOI: 10.1002/adom.201600599 Version of Record online: 11 OCT 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall but I did manage to get my hands on a copy. So here are a few highlights from the paper,

Pigment-based colorants are used for applications ranging from textiles to packaging to cosmetics.[1] However, structural-based alternatives can be more vibrant, durable, and eco-friendly relative to pigmentary colors.[2] Moreover, optical nanostructures are highly tunable, they can achieve a full color gamut by slight alterations to spacing.[3] However, light interference and/or diffraction from most photonic structures results in iridescence,[4] which limits their broader applications. Iridescent colors that change hue when viewed from different directions are useful for niche markets, such as security and anticounterfeiting, {emphasis mine} [5] but are not desirable for most applications, such as paints, coatings, electronic displays, and apparels. Hence, fabricating a photonic structure that minimizes iridescence is a key step to unlocking the potential applications of structural colors.

Noniridescent structural colors in nature are produced by coherent scattering of light by quasi-ordered, amorphous photonic structures (i.e., photonic glass),[6–10] or photonic polycrystals [9,11–14] that possess only short-range order. Iridescence is thought to be a fundamental component of photonic structures with long-range order, such as multilayers.[4] However, the complexity of short-range order photonic structures prohibits their design and fabrication using top-down approaches while bottom-up synthesis using colloidal suspension[15,16] or self-assembly[17–20] lack the tight controls over the spatial and temporal scales needed for industrial mass production. Photonic structures with long-range order are easier to model mathematically. Hence, long-range order photonic structures are intrinsically suitable for top-down fabrication, where precise feature placement and scalability can be guaranteed.

Recently, we found blue color produced by multilayer interference on specialized hairs from two species of blue tarantulas (Poecilotheria metallica (Figure 1a,b) and Lampropelma violaceopes) that was largely angle independent.[21] We hypothesize that the iridescent effects of the multilayer are reduced by hierarchical structuring of the hairs. Specifically, the hairs have: (1) high degrees of rotational symmetry, (2) hierarchy—with subcylindrical multilayers surrounding a larger, overarching multilayer cylinder, and (3) nanoscale surface grooves. Because all of these structures co-occur on the tarantulas, it is impossible to decouple them simply by observing nature. Here, we use optical simulation and nano-3D rapid prototyping to demonstrate that introducing design features seen in these tarantulas onto a multilayer photonic structure nearly eliminates iridescence. As far as we are aware, this is the first known example of a noniridescent structural color produced by a photonic structure with both short and long-range order. This opens up an array of new possibilities for photonic structure design and fabrication to produce noniridescent structural colors and is a key first step to achieving economically viable solutions for mass production of noniridescent structural color.  … (p. 1 PDF)

There is a Canadian security and anti-counterfeiting company (Nanotech Security Corp.), inspired by the Morpho butterfly and its iridescent blue, which got its start in Bozena Kaminska’s laboratory at Simon Fraser University (Vancouver, Canada).

Getting back to the paper, after a few twists and turns, they conclude with this,

This approach of producing noniridescent structural colors using photonic structures with long-range order (i.e., modified multilayer) has, to our knowledge, not been explored previously. Our findings reaffirm the value of using nature and the biomimetic process as a tool for innovation and our approach also may help to overcome the current inability of colloidal self-assembly to achieve pure noniridescent structural red due to single-particle scattering and/or multiple scattering.[25] As a result, our research provides a new and easy way for designing structural colorants with customizable hues (see Figure S6, Supporting Information, as one of the potential examples) and iridescent effects to satisfy the needs of different applications. While nano-3D printing of these nanostructures is not viable for mass production, it does identify the key features that are necessary for top-down fabrication. With promising nanofabrication techniques, such as preform drawing[26]—a generally scalable methodology that has been demonstrated for fabricating particles with complex internal architectures and continuously tunable diameters down to nanometer scale[27] – it is possible to mass produce these “designer structural colorants” in an economically viable manner. Our discovery of how to produce noniridescent structural colors using long-range order may therefore lead to a more sustainable future that does not rely upon toxic and wasteful synthetic pigments and dyes. (p. 5)

I’m glad to have gotten caught up with the work. Thank you, Bor-Kai Hsiung.

Nanotech Security Corp. stock declining but Cantor Fitzgerald Canada analyst Ralph Garcea gives the stock a buy rating

Linda Rogers has written a Feb. 29, 2016 article about a Vancouver-based company rather perturbingly titled ‘What’s Propelling Nanotech Security Corp to Decline So Much?‘ for Small Cap Wired,

The stock of Nanotech Security Corp (CVE:NTS) is a huge mover today! The stock is down 3.23% or $0.04 after the news [Nanotech Security announced its first quarter fiscal 2016 results in a Feb. 29, 2016 news release], hitting $1.2 per share. … The move comes after 7 months negative chart setup for the $68.48M company. It was reported on Feb, 29 [2016] by Barchart.com. We have $1.06 PT which if reached, will make CVE:NTS worth $8.22 million less.

The Feb. 29, 2016 Nanotech Security news release (summary version) highlights the good news first,

  • Revenue of $1.5 million consistent with the same period last year.  Security Features contributed revenues of $569,000 largely from development contracts and Surveillance delivered $940,000.
  • Gross margin improved to 50% up from 34% in the same period last year.  The improvement reflects the increased mix of higher margin Security Features revenue.
  • Renewed a $1.0 million banknote security feature development contract. The Company successfully renewed the third and final phase of a banknote development contract with a top ten issuing authority to develop a unique Optically Variable Device (“OVD”) security feature for incorporation into future banknotes.  The final phase is expected to generate revenues of approximately $1.0 million.
  • Signed new $3.0 million KolourOptik banknote development contract. The Company signed a new three phase development contract to use the KolourOptik™ nanotechnology to develop a unique OVD security features with another G8 country for incorporation into future banknotes.
  • Strategic meetings with large international banknote issuing authority.  The Company continues to work with a large international banknote issuing authority to deliver a significant volume of colour shifting Optical Thin Film (“OTF”), and partner with our KolourOptik™ technology.  Management continues to devote a significant amount of time and resources in advancing these opportunities.
  • Signed a Memorandum of Understanding (“MOU”) with Hueck Folien, a European manufacturer to supply OTF to the banknote market.  The MOU contemplates an operational agreement to collaborate in the volume production of a colour shifting OTF security feature.  The OTF product is anticipated to initially be used in banknotes as threads and then expand into other markets in the future.

Doug Blakeway, Nanotech’s Chairman and CEO commented, “These two development contracts are material achievements.  Issuing authorities are paying us – something not common in the industry – to design unique banknote security features with our OTF and KolourOptik™ technologies.”  He further added, “Nanotech’s team has scaled the Hueck Folien production facility to where we believe together we can provide the initial volumes demanded by a top-ten issuing authority.  Our relationship with Hueck Folien continues to funnel security feature opportunities to Nanotech.”

The company’s sadder news can be found in their seven-page Feb. 29, 2016 news release (PDF). Their net earnings for the final quarter of 2015 and 2014 were both losses but in 2014 their loss was (931,271) and in 2015 it was (1,746,335). Still, the company’s gross profit from revenue for the same time periods was 50% in 2015 as opposed to 34% in 2014 despite slightly less revenue in 2015.

Assuming I’ve read this information correctly, Nanotech Security does seem to be in a fragile situation but that can change. After all, IBM was in serious trouble for a number of years during the 1990s when there was even talk the company might go bankrupt. As far as I’m aware, IBM is no longer in imminent danger of disappearing from the scene. *ETA March 9, 2016: It seems I used the wrong example if Robert X. Cringley’s March 9, 2016 article ‘What’s happening at IBM? (It’s dying)‘ for Beta News is to be believed.)* Getting back to my point, companies do go through cycles and it can be difficult to determine exactly what’s happening at some of the earlier stages.

Certainly, Cantor Fitzgerald Canada analyst Ralph Garcea has an optimistic view of Nanotech Security’s prospects according to a March 1, 2016 article by Nick Waddell for cantech letter,

Nanotech Security (TSXV:NTS) offers a better and more secure solution in multiple market segments that together are worth billions of dollars per year, says Cantor Fitzgerald Canada analyst Ralph Garcea.

This morning [March 1, 2016], Garcea initiated coverage of Nanotech with a “Buy” rating and a one-year price target of $2.50, implying a return of 110 per cent at the time of publication.

Garcea notes that Nanotech has already created solutions for the consumer electronics, brand identification and currency segments. He points out that one of the company’s biggest differentiators is that its solution can be embedded onto almost any material. This is important, he says, because it means that security can be embedded into places it previously could not go, such as directly onto a pharmaceutical pill.

Shares of Nanotech Security closed today [March 1, 2016] up 2.5 per cent to $1.22.

I have written about Nanotech Security frequently and believe the most recent is a Dec. 29, 2015 posting. For those unfamiliar with the company’s technology, it’s based on the structures found on the blue morpho butterfly. The holes in the butterfly’s wings lend it certain optical properties which the company mimics for its anti-counterfeiting technology.

One final comment, I am not endorsing the company or any of the analysis of the company’s financial situation and prospects.

Vancouver (Canada) -based NanoTech Security and its tireless self-promotion

First featured here in a January 17, 2011 posting about proposed anti-counterfeiting measures based on the structures present on the Blue Morpho butterfly’s wings, NanoTech Security is the subject of a profile in the Vancouver (Canada) Sun’s Dec. 28, 2015 Technology article by Randy Shore.

They’ve managed to get themselves into the newspaper without having any kind of real news, research or business, to share. As is so often the case, timing is everything. This is a low news period (between Christmas and New Year) and the folks at NanoTech Security got lucky with a reporter who doesn’t know much about the company or the technology. When you add in low public awareness about the company and its products (you couldn’t do this with a company specializing in a well established technology, e.g., smartphones), there’s an opportunity.

Getting back to Shore’s Dec. 28, 2015 Technology article in the Vancouver Sun,

Landrock [Clint Landrock], the chief technology officer at Burnaby-based [Burnaby is a municipality in what’s known as Metro Vancouver] Nanotech Security Corp., has spun off his SFU [Simon Fraser University] research to found the firm, which is developing nano-optics for the global battle against counterfeiters.

Colour-shifting holographic images, used as counterfeit protection on many banknotes, use technology that has been around for more than 35 years and they are increasingly easy to reproduce. Talented hobbyists can duplicate simple holographic features and organized criminals with deeper pockets can reproduce more sophisticated features with the right equipment.

Nanotech Security hopes to take a quantum leap ahead of forgers.

The detail and colour reproduction possible in Nanotech’s KolourOptick are dramatically better than the holographic images used on banknotes.

“We can improve a lot on those, by making the image a lot brighter, have a lot more detail and make it easy to view,” said Landrock. “When you try to fake that, it’s much more difficult to do and when you see a fake it looks fake.”

“Right now, the fake holograms often look better than the real thing,” he said.

Tiny structuresWhat [sic] Landrock found on the wings of the Blue Morpho was a lattice of tiny treelike structures that interact with light, selecting certain wavelengths to create a bright blue hue without pigments.

This ‘origins’ story includes a business mastermind, Doug Blakeway, and the researcher (Bozena Kaminska) under whose supervision Landrock did his work. Blakeway provides a somewhat puzzling quote for Shore’s story,

“I love nanotechnology, but I really have not seen a commercialization of it that can make you money in the near term, [emphasis mine]” said Blakeway. “When this was initially presented to me by Bozena and Clint, I immediately saw their vision and they were only after one application — creating anti-counterfeiting features for banknotes.”

The three formed a private company and licensed the patents from SFU, which receives a three per cent royalty on sales of the technology created under its roof. …

I am perplexed by Blakeway’s ” … I really have not seen a commercialization of it that can make you money in the near term” comment. There are many nanotechnology-enabled products on the market ranging from coatings for superhydrophobic waterproofing products to carbon fibre-enhanced golf clubs to nanoscale chips for computers and components for phones to athletic materials impregnated with silver nanoparticles for their antibacterial properties (clothes you don’t have to wash as often) to cosmetics and beauty products, e.g., nano sunscreens, and there are more.

NanoTech Security’s recently released some information about their financial status. They must feel encouraged by their gains and other business developments (from a Dec. 17, 2015 NanoTech Security news release),

Nanotech Security Corp. (TSXV: NTS) (OTCQX: NTSFF), (“Nanotech” or the “Company”) today released its financial results for the fourth quarter and year ended September 30, 2015.

Strategic Highlights from 2015

Revenue increased to $5.2 million a 131% increase over 2014. Security Features contributed revenues of $3.1 million.
Gross margin improved to 43% up from 34% in the same period last year. The improvement reflects the increased mix of higher margin Security Features revenue.
Signed two banknote security feature development contracts. The contracts are with top ten issuing authorities to develop unique optically-variable security features for incorporation into future banknotes.
Strategic meetings with large international banknote issuing authority. The Company has been approached by a large international banknote issuing authority to deliver a large volume of Optical Thin Film (“OTF”), and partner with our KolourOptik™ technology. Management continues to devote a significant amount of time and resources in advancing these opportunities.
Private Placement. The Company completed a non-brokered private placement financing of $2.6 million in equity units at $1.00 each.
Signed an amending agreement related to the 2014 Fortress Optical purchase agreement. The amendment provides that 1.5 million of the 3.0 million shares held in escrow, pending certain sales milestones were released from escrow and the remaining 1.5 million shares were returned to the treasury. The overall effect of the amendment resulted in a gain of $1.5 million and cancellation of 1.5 million shares.
Demonstrated KolourOptik™ security feature on metal coins. The Company successfully applied nanotechnology images to metal coins in a production environment at an issuing mint.
Granted five new patents expanding the growing IP portfolio. Three patents relate to the Company’s next generation nanotechnology authentication features, and two provide increased protection for OTF.

I’m curious as to how much of their revenue is derived from sales as opposed to research funding and just how much money does a 43% increase in gross margins represent? (Or, perhaps I just need to get better at reading news about *companies* and their finances.) In any event, signing two contracts and gaining interest in applying the technology to metal coins must have been exciting.

This story goes to show that if you understand news cycles, have a little luck and/or know someone, and have a relatively unknown technology or product, it’s possible to get media coverage.

*’company’s’ corrected to ‘companies’.

Business in Vancouver discovers nanotechnology

There’ve been two articles in the Vancouver (Canada) newspaper, Business in Vancouver by Tyler Orton about a Simon Fraser University spin-off (start up) company, Nanotech Security. I first mentioned the not-yet-named company in a January 17, 2011 posting about proposed anti-counterfeiting measures based on the structures present on the Blue Morpho butterfly’s wings.

Orton’s Feb. 24, 2015 piece for Business in Vancouver provides an update on the company and on some of the business issues associated with a new technology and the strategy being used to introduce it,

Colour-shifting optical film has been the industry standard for banknote security since the 1990s. Depending on the angle of view, colours change on security features printed on bills in a way that the average person can recognize.

Because the nanotechnology has yet to be fully commercialized, the optical film side of the business is growing the most.

… increased demand for the optical film products prompted Nanotech to add a second shift at its Quebec cellulose facility, which was acquired – along with the legacy business – from North Vancouver’s Fortress Paper (TSX:FTP) in August.

Fortress Paper CEO Chad Wasilenkoff said when discussions began over the sale of Fortress Optical Features (FOF) he was immediately drawn to Nanotech’s butterfly technology.

“Getting a brand-new security feature that has not been used anywhere before … [banks] are just not willing to take a chance on new things in general when it comes to banknotes,” he told Business in Vancouver.

“It will take a little while to come to fruition, but we think putting these two entities [Nanotech and FOF] together will definitely fast-track that.”

Counterfeiting hit its most recent peak in 2004, when 470 fake notes per million were detected across the country, according to a 2011 Bank of Canada (BoC) study.

Wasilenkoff, whose company operates another banknote security firm in Switzerland, said he was happy with the return on investment after Fortress bought the BoC assets for  $750,000 and sold them to Nanotech three years later for $17.5 million.

“We were able to find a solution that was really synergistic for both companies,” he said, adding that Fortress will receive preferential treatment on new security features Nanotech develops.

LeRoux [Nanotech chief development officer Igi LeRoux] added that acquiring the legacy business was necessary if the nanotechnology was to be taken seriously in an industry that greets upstart companies with skepticism.

“[Now] We have an established network, we have an established market base, we have an existing product and – most importantly – we have an existing reputation in the industry.”

Orton’s Aug. 28, 2015 piece for Business in Vancouver builds on his Feb. work (Note: Links have been removed),

Banknotes implanted with nanotechnology, bills printed with pinhead-sized images at maximum resolution or even coins that can store of data.

… it’s not the kind of out-there concepts that only exists in the mind of the CEO of Nanotech Security [Doug Blakeway].

The Burnaby-based banknote security firm has been working non-stop to get these anti-counterfeiting measures onto the streets as quickly as possible and is preparing to ramp up production and sales of its technology after securing $2.6 million in its latest round of fundraising that closed Wednesday (August 26 [2015]).

Blakeway said the plan is to converge the nanotechnology and the optical film technology soon. It’s a measure he said is necessary to introduce the nanotechnology to issuing authorities that may be skeptical about the new product.

It probably won’t be until November before Nanotech discloses which countries are using its technology. Issuing authorities, Blakeway said, are reluctant to reveal exactly what measures they’re taking to fight counterfeiting.

“You can talk about the top 10 issuing authorities or the G8 issuing authorities,” he said.

But Nanotech isn’t stopping only at imprinting bills with the microscopic holes.

Mints began asking last year if it could transfer its technology onto coins in a stamping operation without any extra cost, save for the dye they use.

Moving forward, the coins will be able to store data through an image that’s carried through light waves.

I trust someone will notify the US government about this proposed nanotechnology-enabled coinage. There have been concerns about Canadian coinage in the past as noted in a May 7, 2007 article in thestar.com by Ted Bridis (Associated Press),

An odd-looking Canadian coin with a bright red flower was the culprit behind the U.S. Defence Department’s false espionage warning earlier this year, the Associated Press has learned.

The odd-looking – but harmless – “poppy coin” was so unfamiliar to suspicious U.S. Army contractors travelling in Canada that they filed confidential espionage accounts about them. The worried contractors described the coins as “anomalous” and “filled with something man-made that looked like nano-technology,” according to once-classified U.S. government reports and e-mails obtained by the AP.

The silver-coloured 25-cent piece features the red image of a poppy – Canada’s flower of remembrance – inlaid over a maple leaf. The unorthodox quarter is identical to the coins pictured and described as suspicious in the contractors’ accounts.

The supposed nano-technology actually was a conventional protective coating the Royal Canadian Mint applied to prevent the poppy’s red color from rubbing off. The mint produced nearly 30 million such quarters in 2004 commemorating Canada’s 117,000 war dead.

“It did not appear to be electronic (analog) in nature or have a power source,” wrote one U.S. contractor, who discovered the coin in the cup holder of a rental car. “Under high power microscope, it appeared to be complex consisting of several layers of clear, but different material, with a wire like mesh suspended on top.”

The confidential accounts led to a sensational warning from the Defence Security Service, an agency of the Defence Department, that mysterious coins with radio frequency transmitters were found planted on U.S. contractors with classified security clearances on at least three separate occasions between October 2005 and January 2006 as the contractors travelled through Canada.

It seems those army contractors were prescient about nanotechnology-enabled coins. As for the potential to use these coins for spying, I leave that speculation to those who know more about the technology.

Tiny gold Archimedes’ spirals and identity theft prevention

There’s more than one way to prevent identity theft and counterfeit currency (there’s more about an approach pioneered in Canada at the end of this post). Scientists at Vanderbilt University and at Pacific Northwest National Laboratory have developed a new technology to achieve those ends, according to a June 3, 2015 news item on Azonano,

Take gold spirals about the size of a dime…and shrink them down about six million times. The result is the world’s smallest continuous spirals: “nano-spirals” with unique optical properties that would be almost impossible to counterfeit if they were added to identity cards, currency and other important objects.

Students and faculty at Vanderbilt University fabricated these tiny Archimedes’ spirals and then used ultrafast lasers at Vanderbilt and the Pacific Northwest National Laboratory in Richland, Washington, to characterize their optical properties. The results are reported in a paper published online by the Journal of Nanophotonics on May 21 [2015].

A June 2, 2015 Vanderbilt University news release, which originated the news item, describes how the research was approached,

“They are certainly smaller than any of the spirals we’ve found reported in the scientific literature,” said Roderick Davidson II, the Vanderbilt doctoral student who figured out how to study their optical behavior. The spirals were designed and made at Vanderbilt by another doctoral student, Jed Ziegler, now at the Naval Research Laboratory.

Most other investigators who have studied the remarkable properties of microscopic spirals have done so by arranging discrete nanoparticles in a spiral pattern: similar to spirals drawn with a series of dots of ink on a piece of paper. By contrast, the new nano-spirals have solid arms and are much smaller: A square array with 100 nano-spirals on a side is less than a hundredth of a millimeter wide.

When these spirals are shrunk to sizes smaller than the wavelength of visible light, they develop unusual optical properties. For example, when they are illuminated with infrared laser light, they emit visible blue light. A number of crystals produce this effect, called frequency doubling or harmonic generation, to various degrees. The strongest frequency doubler previously known is the synthetic crystal beta barium borate, but the nano-spirals produce four times more blue light per unit volume.

When infrared laser light strikes the tiny spirals, it is absorbed by electrons in the gold arms. The arms are so thin that the electrons are forced to move along the spiral. Electrons that are driven toward the center absorb enough energy so that some of them emit blue light at double the frequency of the incoming infrared light.

“This is similar to what happens with a violin string when it is bowed vigorously,” said Stevenson Professor of Physics Richard Haglund, who directed the research. “If you bow a violin string very lightly it produces a single tone. But, if you bow it vigorously, it also begins producing higher harmonics, or overtones. The electrons at the center of the spirals are driven pretty vigorously by the laser’s electric field. The blue light is exactly an octave higher than the infrared – the second harmonic.”

The nano-spirals also have a distinctive response to polarized laser light. Linearly polarized light, like that produced by a Polaroid filter, vibrates in a single plane. When struck by such a light beam, the amount of blue light the nano-spirals emit varies as the angle of the plane of polarization is rotated through 360 degrees.

The effect is even more dramatic when circularly polarized laser light is used. In circularly polarized light, the polarization plane rotates either clockwise or counterclockwise. When left-handed nano-spirals are illuminated with clockwise polarized light, the amount of blue light produced is maximized because the polarization pushes the electrons toward the center of the spiral. Counterclockwise polarized light, on the other hand, produces a minimal amount of blue light because the polarization tends to push the electrons outward so that the waves from all around the nano-spiral interfere destructively.

The news release goes on to explain how the properties of these gold nanospirals can be applied to identity theft protection and anti-counterfeiting measures,

The combination of the unique characteristics of their frequency doubling and response to polarized light provide the nano-spirals with a unique, customizable signature that would be extremely difficult to counterfeit, the researchers said.

So far, Davidson has experimented with small arrays of gold nano-spirals on a glass substrate made using scanning electron-beam lithography. Silver and platinum nano-spirals could be made in the same way. Because of the tiny quantities of metal actually used, they can be made inexpensively out of precious metals, which resist chemical degradation. They can also be made on plastic, paper and a number of other substrates.

“If nano-spirals were embedded in a credit card or identification card, they could be detected by a device comparable to a barcode reader,” said Haglund.

The frequency doubling effect is strong enough so that arrays that are too small to see with the naked eye can be detected easily. That means they could be placed in a secret location on a card, which would provide an additional barrier to counterfeiters.

The researchers also argue that coded nano-spiral arrays could be encapsulated and placed in explosives, chemicals and drugs – any substance that someone wants to track closely – and then detected using an optical readout device.

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

Eflcient forward second-harmonic generation from planar archimedean nanospirals by Roderick B. Davidson II,  Jed I. Ziegler,Guillermo Vargas, Sergey M. Avanesyan, Yu Gong, Wayne Hess, & Richard F. Haglund Jr. Nanophotonics. Volume 4, Issue 1, ISSN (Online) 2192-8614, DOI: 10.1515/nanoph-2015-0002, May 2015

This paper is open access.

The researchers have provided an image,

Scanning electron microscope image of an individual nano-spiral. (Haglund Lab / Vanderbilt)

Scanning electron microscope image of an individual nano-spiral. (Haglund Lab / Vanderbilt)

This works brings to mind Nanotech Security, a Vancouver (Canada) -based company that provides anti-counterfeiting measures derived from observations made of the Blue Morpho butterfly and the nanostructures on its wings. My latest post about the technology, a June 1, 2015 piece, describes the company’s latest patents and my earliest post, a Jan. 17, 2011 piece, features the first laboratory announcement about the butterfly, the work, and hopes for the technology.

Iridescent bird feathers inspire synthetic melanin for structural color/colour

I’m hoping one day they’ll be able to create textiles that rely on structure rather than pigment or dye for colour so my clothing will no longer fade with repeated washings and exposure to sunlight. There was one such textile, morphotex (named for the Blue Morpho butterfly, no longer produced by Japanese manufacturer Teijin but you can see a photo of the fabric which was fashioned into a dress by Australian designer Donna Sgro in my July 19, 2010 posting.

This particular project at the University of California at San Diego (UCSD), sadly, is not textile-oriented, but has resulted in a film according to a May 13, 2015 news item on ScienceDaily,

Inspired by the way iridescent bird feathers play with light, scientists have created thin films of material in a wide range of pure colors — from red to green — with hues determined by physical structure rather than pigments.

Structural color arises from the interaction of light with materials that have patterns on a minute scale, which bend and reflect light to amplify some wavelengths and dampen others. Melanosomes, tiny packets of melanin found in the feathers, skin and fur of many animals, can produce structural color when packed into solid layers, as they are in the feathers of some birds.

“We synthesized and assembled nanoparticles of a synthetic version of melanin to mimic the natural structures found in bird feathers,” said Nathan Gianneschi, a professor of chemistry and biochemistry at the University of California, San Diego. “We want to understand how nature uses materials like this, then to develop function that goes beyond what is possible in nature.”

A May 13, 2015 UCSD news release by Susan Brown (also on EurekAlert), which originated the news item, describes the inspiration and the work in more detail,

Gianneschi’s work focuses on nanoparticles that can sense and respond to the environment. He proposed the project after hearing Matthew Shawkey, a biology professor at the University of Akron, describe his work on the structural color in bird feathers at a conference. Gianneschi, Shawkey and colleagues at both universities report the fruits of the resulting collaboration in the journal ACS Nano, posted online May 12 [2015].

To mimic natural melanosomes, Yiwen Li, a postdoctoral fellow in Gianneschi’s lab, chemically linked a similar molecule, dopamine, into meshes. The linked, or polydopamine, balled up into spherical particles of near uniform size. Ming Xiao, a graduate student who works with Shawkey and polymer science professor Ali Dhinojwala at the University of Akron, dried different concentrations of the particles to form thin films of tightly packed polydopamine particles.

The films reflect pure colors of light; red, orange, yellow and green, with hue determined by the thickness of the polydopamine layer and how tightly the particles packed, which relates to their size, analysis by Shawkey’s group determined.

The colors are exceptionally uniform across the films, according to precise measurements by Dimitri Deheyn, a research scientist at UC San Diego’s Scripps Institution of Oceanography who studies how a wide variety of organisms use light and color to communicate. “This spatial mapping of spectra also tells you about color changes associated with changes in the size or depth of the particles,” Deheyn said.

The qualities of the material contribute to its potential application. Pure hue is a valuable trait in colorimetric sensors. And unlike pigment-based paints or dyes, structural color won’t fade. Polydopamine, like melanin, absorbs UV light, so coatings made from polydopamine could protect materials as well. Dopamine is also a biological molecule used to transmit information in our brains, for example, and therefore biodegradable.

“What has kept me fascinated for 15 years is the idea that one can generate colors across the rainbow through slight (nanometer scale) changes in structure,” said Shawkey whose interests range from the physical mechanisms that produce colors to how the structures grow in living organisms. “This idea of biomimicry can help solve practical problems but also enables us to test the mechanistic and developmental hypotheses we’ve proposed,” he said.

Natural melanosomes found in bird feathers vary in size and particularly shape, forming rods and spheres that can be solid or hollow. The next step is to vary the shapes of nanoparticles of polydopamine to mimic that variety to experimentally test how size and shape influence the particle’s interactions with light, and therefore the color of the material. Ultimately, the team hopes to generate a palette of biocompatible, structural color.

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

Bio-Inspired Structural Colors Produced via Self-Assembly of Synthetic Melanin Nanoparticles by Ming Xiao, Yiwen Li, Michael C. Allen, Dimitri D. Deheyn, Xiujun Yue, Jiuzhou Zhao, Nathan C. Gianneschi, Matthew D. Shawkey, and Ali Dhinojwala. ACS Nano, Article ASAP DOI: 10.1021/acsnano.5b01298 Publication Date (Web): May 4, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

For anyone who’d like to explore structural colour further, there’s this Feb. 7, 2013 posting which features excerpts from and a link to an excellent article by Cristina Luiggi for The Scientist.