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Australian peacock spiders, photonic nanostructures, and making money

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Researcher Bor-Kai Hsiung’s work has graced this blog before but the topic was tarantulas and their structural colour. This time, it’s all about Australian peacock spiders and their structural colour according to a December 22, 2017 news item on ScienceDaily,

Even if you are arachnophobic, you probably have seen pictures or videos of Australian peacock spiders (Maratus spp.). These tiny spiders are only 1-5 mm long but are famous for their flamboyant courtship displays featuring diverse and intricate body colorations, patterns, and movements.

The spiders extremely large anterior median eyes have excellent color vision and combine with their bright colors to make peacock spiders cute enough to cure most people of their arachnophobia. But these displays aren’t just pretty to look at, they also inspire new ways for humans to produce color in technology.

One species of peacock spider — the rainbow peacock spider (Maratus robinsoni) is particularly neat, because it showcases an intense rainbow iridescent signal in males’ courtship displays to the females. This is the first known instance in nature of males using an entire rainbow of colors to entice females. Dr. Bor-Kai Hsiung led an international team of researchers from the US (UAkron, Cal Tech, UC San Diego, UNL [University of Nebraska-Lincoln]), Belgium (Ghent University), Netherlands (UGroningen), and Australia to discover how rainbow peacock spiders produce this unique multi-color iridescent signal.

A December 22, 2017 Ghent University (Belgium) press release on Alpha Galileo, which originated the news item, provides more technical detail,

Using a diverse array of research techniques, including light and electron microscopy, hyperspectral imaging, imaging scatterometry, nano 3D printing and optical modeling, the team found the origin of this intense rainbow iridescence emerged from specialized abdominal scales of the spiders. These scales have an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface.

The interaction between the surface nano-diffraction grating and the microscopic curvature of the scales enables separation and isolation of light into its component wavelengths at finer angles and smaller distances than are possible with current manmade engineering technologies.

Inspiration from these super iridescent scales can be used to overcome current limitations in spectral manipulation, and to further reduce the size of optical spectrometers for applications where fine-scale spectral resolution is required in a very small package, notably instruments on space missions, or wearable chemical detection systems. And it could have a wide array of implications to fields ranging from life sciences and biotechnologies to material sciences and engineering.

Here’s a video of an Australian rainbow peacock spider,

Here’s more from the YouTube description published on April 13, 2017 by Peacockspiderman,

Scenes of Maratus robinsoni, a spider Peter Robinson discovered and David Hill and I named it after him in 2012. You can read our description on pages 36-41 in Peckhamia 103.2, which can be downloaded from the Peckhamia website http://peckhamia.com/peckhamia_number…. This is one of the two smallest species of peacock spider (2.5 mm long) and the only spider we know of in which colour changes occur every time it moves, this video was created to document this. Music: ‘Be Still’ by Johannes Bornlöf licensed through my MCN ‘Brave Bison’ from ‘Epidemic Sound’ For licensing inquiries please contact Brave Bison licensing@bravebison.io

The University of California at San Diego also published a December 22, 2017 news release about this work, which covers some of the same ground while providing a few new tidbits of information,

Brightly colored Australian peacock spiders (Maratus spp.) captivate even the most arachnophobic viewers with their flamboyant courtship displays featuring diverse and intricate body colorations, patterns, and movements – all packed into miniature bodies measuring less than five millimeters in size for many species. However, these displays are not just pretty to look at. They also inspire new ways for humans to produce color in technology.

One species of peacock spider – the rainbow peacock spider (Maratus robinsoni) – is particularly impressive, because it showcases an intense rainbow iridescent signal in males’ courtship displays to females. This is the first known instance in nature of males using an entire rainbow of colors to entice females to mate. But how do males make their rainbows? A new study published in Nature Communications looked to answer that question.

Figuring out the answers was inherently interdisciplinary so Bor-Kai Hsiung, a postdoctoral scholar at Scripps Institution of Oceanography at the University of California San Diego, assembled an international team that included biologists, physicists and engineers. Starting while he was a Ph.D. student at The University of Akron under the mentorship of Todd Blackledge and Matthew Shawkey, the team included researchers from UA, Scripps Oceanography, California Institute of Technology, and University of Nebraska-Lincoln, the University of Ghent in Belgium, University of Groningen in Netherlands, and Australia to discover how rainbow peacock spiders produce this unique iridescent signal.

The team investigated the spider’s photonic structures using techniques that included light and electron microscopy, hyperspectral imaging, imaging scatterometry and optical modeling to generate hypotheses about how the spider’s scale generate such intense rainbows. The team then used cutting-edge nano 3D printing to fabricate different prototypes to test and validate their hypotheses. In the end, they found that the intense rainbow iridescence emerged from specialized abdominal scales on the spiders. These scales combine an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface. It is the interaction between the surface nano-diffraction grating and the microscopic curvature of the scales that enables separation and isolation of light into its component wavelengths at finer angles and smaller distances than are possible with current engineering technologies.

“Who knew that such a small critter would create such an intense iridescence using extremely sophisticated mechanisms that will inspire optical engineers,” said Dimitri Deheyn, Hsuing’s advisor at Scripps Oceanography and a coauthor of the study.

For Hsiung, the finding wasn’t quite so unexpected.

“One of the main questions that I wanted to address in my Ph.D. dissertation was ‘how does nature modulate iridescence?’ From a biomimicry perspective, to fully understand and address a question, one has to take extremes from both ends into consideration. I purposefully chose to study these tiny spiders with intense iridescence after having investigated the non-iridescent blue tarantulas,” said Hsiung.

The mechanism behind these tiny rainbows may inspire new color technology, but would not have been discovered without research combining basic natural history with physics and engineering, the researchers said.

“Nanoscale 3D printing allowed us to experimentally validate our models, which was really exciting,” said Shawkey. “We hope that these techniques will become common in the future.”

“As an engineer, what I found fascinating about these spider structural colors is how these long evolved complex structures can still outperform human engineering,” said Radwanul Hasan Siddique, a postdoctoral scholar at Caltech and study coauthor. “Even with high-end fabrication techniques, we could not replicate the exact structures. I wonder how the spiders assemble these fancy structural patterns in the first place!”

Inspiration from these super iridescent spider scales can be used to overcome current limitations in spectral manipulation, and to reduce the size of optical spectrometers for applications where fine-scale spectral resolution is required in a very small package, notably instruments on space missions, or wearable chemical detection systems.

In the end, peacock spiders don’t just produce nature’s smallest rainbows.They could also have implications for a wide array of fields ranging from life sciences and biotechnologies to material sciences and engineering.

Before citing the paper and providing a link, here’s a story by Robert F. Service for Science magazine about attempts to capitalize on ‘spider technology’, in this case spider silk,

The hype over spider silk has been building since 1710. That was the year François Xavier Bon de Saint Hilaire, president of the Royal Society of Sciences in Montpellier, France, wrote to his colleagues, “You will be surpriz’d to hear, that Spiders make a Silk, as beautiful, strong and glossy, as common Silk.” Modern pitches boast that spider silk is five times stronger than steel yet more flexible than rubber. If it could be made into ropes, a macroscale web would be able to snare a jetliner.

The key word is “if.” Researchers first cloned a spider silk gene in 1990, in hopes of incorporating it into other organisms to produce the silk. (Spiders can’t be farmed like silkworms because they are territorial and cannibalistic.) Today, Escherichia coli bacteria, yeasts, plants, silkworms, and even goats have been genetically engineered to churn out spider silk proteins, though the proteins are often shorter and simpler than the spiders’ own. Companies have managed to spin those proteins into enough high-strength thread to produce a few prototype garments, including a running shoe by Adidas and a lightweight parka by The North Face. But so far, companies have struggled to mass produce these supersilks.

Some executives say that may finally be about to change. One Emeryville, California-based startup, Bolt Threads, says it has perfected growing spider silk proteins in yeast and is poised to turn out tons of spider silk thread per year. In Lansing, Michigan, Kraig Biocraft Laboratories says it needs only to finalize negotiations with silkworm farms in Vietnam to produce mass quantities of a combination spider/silkworm silk, which the U.S. Army is now testing for ballistics protection. …

I encourage you to read Service’s article in its entirety if the commercialization prospects for spider silk interest you as it includes gems such as this,

Spider silk proteins are already making their retail debut—but in cosmetics and medical devices, not high-strength fibers. AMSilk grows spider silk proteins in E. coli and dries the purified protein into powders or mixes it into gels, for use as additives for personal care products, such as moisture-retaining skin lotions. The silk proteins supposedly help the lotions form a very smooth, but breathable, layer over the skin. Römer says the company now sells tons of its purified silk protein ingredients every year.

…

Finally, here’s a citation for and a link to the paper about Australian peacock spiders and nanophotonics,

Rainbow peacock spiders inspire miniature super-iridescent optics by Bor-Kai Hsiung, Radwanul Hasan Siddique, Doekele G. Stavenga, Jürgen C. Otto, Michael C. Allen, Ying Liu, Yong-Feng Lu, Dimitri D. Deheyn, Matthew D. Shawkey, & Todd A. Blackledge. Nature Communications 8, Article number: 2278 (2017) doi:10.1038/s41467-017-02451-x Published online: 22 December 2017

This paper is open access.

As for Bor-Kai Hsiung’s other mentions here:

How tarantulas get blue (December 7, 2015 posting)

Noniridescent photonics inspired by tarantulas (October 19, 2016 posting)

More on the blue tarantula noniridescent photonics (December 28, 2016 posting)

Gold nanoparticle clusters: four new models

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This research is being done at the University of Nebraska-Lincoln (UNL) which seems to be on a publishing tear lately. From an April 27, 2015 news item on Nanowerk, here’s the latest,

They may deal in gold, atomic staples and electron volts rather than cement, support beams and kilowatt-hours, but chemists have drafted new nanoscale blueprints for low-energy structures capable of housing pharmaceuticals and oxygen atoms.

Led by UNL’s Xiao Cheng Zeng and former visiting professor Yi Gao, new research has revealed four atomic arrangements of a gold nanoparticle cluster. The arrangements exhibit much lower potential energy and greater stability than a standard-setting configuration reported last year by a Nobel Prize-winning team from Stanford University.

The modeling of these arrangements could inform the cluster’s use as a transporter of pharmaceutical drugs and as a catalyst for removing pollutants from vehicular emissions or other industrial byproducts, Zeng said.

An April 24, 2015 UNL news release (also on EurekAlert), which originated the news item, provides more technical details about the work,

Led by UNL’s Xiao Cheng Zeng and former visiting professor Yi Gao, new research has revealed four atomic arrangements of a gold nanoparticle cluster. The arrangements exhibit much lower potential energy and greater stability than a standard-setting configuration reported last year by a Nobel Prize-winning team from Stanford University.

The modeling of these arrangements could inform the cluster’s use as a transporter of pharmaceutical drugs and as a catalyst for removing pollutants from vehicular emissions or other industrial byproducts, Zeng said.

Zeng and his colleagues unveiled the arrangements for a molecule featuring 68 gold atoms and 32 pairs of bonded sulfur-hydrogen atoms. Sixteen of the gold atoms form the molecule’s core; the remainder bond with the sulfur and hydrogen to form a protective coating that stems from the core.

Differences in atomic arrangements can alter molecular energy and stability, with less potential energy making for a more stable molecule. The team calculates that one of the arrangements may represent the most stable possible structure in a molecule with its composition.

“Our group has helped lead the front on nano-gold research over the past 10 years,” said Zeng, an Ameritas University Professor of chemistry. “We’ve now found new coating structures of much lower energy, meaning they are closer to the reality than (previous) analyses. So the deciphering of this coating structure is major progress.”

…

The structure of the molecule’s gold core was previously detailed by the Stanford team. Building on this, Zeng and his colleagues used a computational framework dubbed “divide-and-protect” to configure potential arrangements of the remaining gold atoms and sulfur-hydrogen pairs surrounding the core.

The researchers already knew that the atomic coating features staple-shaped linkages of various lengths. They also knew the potential atomic composition of each short, medium and long staple — such as the fact that a short staple consists of two sulfur atoms bonded with one gold.

By combining this information with their knowledge of how many atoms reside outside the core, the team reduced the number of potential arrangements from millions to mere hundreds.

“We divided 32 into the short, middle and long (permutations),” said Zeng, who helped develop the divide-and-protect approach in 2008. “We lined up all those possible arrangements, and then we computed their energies to find the most stable ones.

“Without those rules, it’s like finding a needle in the Platte River. With them, it’s like finding a needle in the fountain outside the Nebraska Union. It’s still hard, but it’s much more manageable. You have a much narrower range.”

The researchers resorted to the computational approach because of the difficulty of capturing the structure via X-ray crystallography or single-particle transmission electron microscopy, two of the most common imaging methods at the atomic scale.

Knowing the nanoparticle’s most stable configurations, Zeng said, could allow biomedical engineers to identify appropriate binding sites for drugs used to treat cancer and other diseases. The findings could also optimize the use of gold nanoparticles in catalyzing the oxidation process that transforms dangerous carbon monoxide emissions into the less noxious carbon dioxide, he said.

Here’s an image illustrating the work,

This rendering shows the atomic arrangements of a gold nanocluster as reported in a new study led by UNL chemist Xiao Cheng Zeng. The cluster measures about 1.7 nanometers long -- roughly the same length that a human fingernail grows in two seconds. (Joel Brehm/Office of Research and Economic Development)

This rendering shows the atomic arrangements of a gold nanocluster as reported in a new study led by UNL chemist Xiao Cheng Zeng. The cluster measures about 1.7 nanometers long — roughly the same length that a human fingernail grows in two seconds. (Joel Brehm/Office of Research and Economic Development)

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

Unraveling structures of protection ligands on gold nanoparticle Au68(SH)32 by Wen Wu Xu, Yi Gao, and Xiao Cheng Zeng. Science Advances 24 Apr 2015: Vol. 1 no. 3 e1400211 DOI: 10.1126/sciadv.1400211

This is an open access article.

As for the Stanford University team’s work mentioned in the news release, I believe it’s from the Roger Kornberg (Nobel laureate) Laboratory. There’s more about that team’s work in an Aug. 21, 2014 article (A new gold standard for nano; Note: A link has been removed) by David Bradley for Chemistry World,

Characterising gold nanoparticles at atomic resolution might improve our understanding of the catalytic activity of these materials, according to an international team. These researchers have now demonstrated that it is possible to use electron microscopy to obtain data on at least one gold cluster of greater than 1nm diameter and to validate the results by comparison with small-angle x-ray scattering data, infrared absorption spectra and density functional theory calculations.

Here’s a link to and a citation for the 2014 paper,

Electron microscopy of gold nanoparticles at atomic resolution by Maia Azubel, Jaakko Koivisto, Sami Malola, David Bushnell, Greg L. Hura, Ai Leen Koh, Hironori Tsunoyama, Tatsuya Tsukuda, Mika Pettersson, Hannu Häkkinen, & Roger D. Kornberg. Science 22 August 2014: Vol. 345 no. 6199 pp. 909-912 DOI: 10.1126/science.1251959

This paper is behind a paywall.

The most recent posting here about gold nanoparticles is an April 14, 2015 piece titled: Gold atoms: sometimes they’re a metal and sometimes they’re a molecule.