Tag Archives: bioinspired

Get better protection from a sunscreen with a ‘flamenco dancing’ molecule?

Caption: illustrative image for the University of Warwick research on ‘Flamenco dancing’ molecule could lead to better-protecting sunscreen created by Dr. Michael Horbury. Credit:: created by Dr Michael Horbury

There are high hopes (more about why later) for a plant-based ‘flamenco dancing molecule’ and its inclusion in sunscreens as described in an October 18, 2019 University of Warwick press release (also on EurekAlert),

A molecule that protects plants from overexposure to harmful sunlight thanks to its flamenco-style twist could form the basis for a new longer-lasting sunscreen, chemists at the University of Warwick have found, in collaboration with colleagues in France and Spain. Research on the green molecule by the scientists has revealed that it absorbs ultraviolet light and then disperses it in a ‘flamenco-style’ dance, making it ideal for use as a UV filter in sunscreens.

The team of scientists report today, Friday 18th October 2019, in the journal Nature Communications that, as well as being plant-inspired, this molecule is also among a small number of suitable substances that are effective in absorbing light in the Ultraviolet A (UVA) region of wavelengths. It opens up the possibility of developing a naturally-derived and eco-friendly sunscreen that protects against the full range of harmful wavelengths of light from the sun.

The UV filters in a sunscreen are the ingredients that predominantly provide the protection from the sun’s rays. In addition to UV filters, sunscreens will typically also include:

Emollients, used for moisturising and lubricating the skin
Thickening agents
Emulsifiers to bind all the ingredients
Other components that improve aesthetics, water resistance, etc.

The researchers tested a molecule called diethyl sinapate, a close mimic to a molecule that is commonly found in the leaves of plants, which is responsible for protecting them from overexposure to UV light while they absorb visible light for photosynthesis.

They first exposed the molecule to a number of different solvents to determine whether that had any impact on its (principally) light absorbing behaviour. They then deposited a sample of the molecule on an industry standard human skin mimic (VITRO-CORNEUM®) where it was irradiated with different wavelengths of UV light. They used the state-of-the-art laser facilities within the Warwick Centre for Ultrafast Spectroscopy to take images of the molecule at extremely high speeds, to observe what happens to the light’s energy when it’s absorbed in the molecule in the very early stages (millionths of millionths of a second). Other techniques were also used to establish longer term (many hours) properties of diethyl sinapate, such as endocrine disruption activity and antioxidant potential.

Professor Vasilios Stavros from the University of Warwick, Department of Chemistry, who was part of the research team, explains: “A really good sunscreen absorbs light and converts it to harmless heat. A bad sunscreen is one that absorbs light and then, for example, breaks down potentially inducing other chemistry that you don’t want. Diethyl sinapate generates lots of heat, and that’s really crucial.”

When irradiated the molecule absorbs light and goes into an excited state but that energy then has to be disposed of somehow. The team of researchers observed that it does a kind of molecular ‘dance’ a mere 10 picoseconds (ten millionths of a millionth of a second) long: a twist in a similar fashion to the filigranas and floreos hand movements of flamenco dancers. That causes it to come back to its original ground state and convert that energy into vibrational energy, or heat.

It is this ‘flamenco dance’ that gives the molecule its long-lasting qualities. When the scientists bombarded the molecule with UVA light they found that it degraded only 3% over two hours, compared to the industry requirement of 30%.

Dr Michael Horbury, who was a Postgraduate Research Fellow at The University Warwick when he undertook this research (and now at the University of Leeds) adds: “We have shown that by studying the molecular dance on such a short time-scale, the information that you gain can have tremendous repercussions on how you design future sunscreens.
Emily Holt, a PhD student in the Department of Chemistry at the University of Warwick who was part of the research team, said: “The next step would be to test it on human skin, then to mix it with other ingredients that you find in a sunscreen to see how those affect its characteristics.”

Professor Florent Allais and Dr Louis Mouterde, URD Agro-Biotechnologies Industrielles at AgroParisTech (Pomacle, France) commented: “What we have developed together is a molecule based upon a UV photoprotective molecule found in the surface of leaves on a plant and refunctionalised it using greener synthetic procedures. Indeed, this molecule has excellent long-term properties while exhibiting low endocrine disruption and valuable antioxidant properties.”

Professor Laurent Blasco, Global Technical Manager (Skin Essentials) at Lubrizol and Honorary Professor at the University of Warwick commented: “In sunscreen formulations at the moment there is a lack of broad-spectrum protection from a single UV filter. Our collaboration has gone some way towards developing a next generation broad-spectrum UV filter inspired by nature. Our collaboration has also highlighted the importance of academia and industry working together towards a common goal.”

Professor Vasilios Stavros added, “Amidst escalating concerns about their impact on human toxicity (e.g. endocrine disruption) and ecotoxicity (e.g. coral bleaching), developing new UV filters is essential. We have demonstrated that a highly attractive avenue is ‘nature-inspired’ UV filters, which provide a front-line defence against skin cancer and premature skin aging.”

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

Towards symmetry driven and nature inspired UV filter design by Michael D. Horbury, Emily L. Holt, Louis M. M. Mouterde, Patrick Balaguer, Juan Cebrián, Laurent Blasco, Florent Allais & Vasilios G. Stavros. Nature Communications volume 10, Article number: 4748 (2019) DOI: https://doi.org/10.1038/s41467-019-12719-z

This paper is open access.

Why the high hopes?

Briefly (the long story stretches over 10 years), the most recommended sunscreens today (2020) are ‘mineral-based’. This is painfully amusing because civil society groups (activists) such as Friends of the Earth (in particular the Australia chapter under Georgia Miller’s leadership) and Canada’s own ETC Group had campaigned against these same sunscreen when they were billed as being based on metal oxide nanoparticles such zinc oxide and/or titanium oxide. The ETC Group under Pat Roy Mooney’s leadership didn’t press the campaign after an initial push. As for Australia and Friend of the Earth, their anti-metallic oxide nanoparticle sunscreen campaign didn’t work out well as I noted in a February 9, 2012 posting and with a follow-up in an October 31, 2012 posting.

The only civil society group to give approval (very reluctantly) was the Environmental Working Group (EWG) as I noted in a July 9, 2009 posting. They had concerns about the fact that these ingredients are metallic but after a thorough of then available research, EWG gave the sunscreens a passing grade and noted, in their report, that they had more concerns about the use of oxybenzone in sunscreens. That latter concern has since been flagged by others (e.g., the state of Hawai’i) as noted in my July 6, 2018 posting.

So, rebranding metallic oxides as minerals has allowed the various civil society groups to support the very same sunscreens many of them were advocating against.

In the meantime, scientists continue work on developing plant-based sunscreens as an improvement to the ‘mineral-based’ sunscreens used now.

Bacterial cellulose nanofibers made strong and tough

Despite all the promise that nanocellulose offers, scientists don’t seem to have found significant applications for the material . In the software industry, they used to call it ‘a killer app’, i.e., an application everyone would start using (e.g. Facebook or Google) thereby making much money for its developer(s)..

This July 31, 2019 news item on phys.org describes research that may help scientists develop a nanocellulose ‘killer app’,

High-performance biomass-based nanocomposites are emerging as promising materials for future structural and functional applications due to their environmentally friendly, renewable and sustainable characteristics. Bio-sourced nanocelluloses [sic] (a kind of nanofibers [sic]) obtained from plants and bacterial fermentation are the most abundant raw materials on earth. They have attracted tremendous attention recently due to their attractive inherent merits including biodegradability, low density, thermal stability, global availability from renewable resources, as well as impressive mechanical properties. These features make them appropriate building blocks for spinning the next generation of advanced macrofibers for practical applications.

In past decades, various strategies have been pursued to gain cellulose-based macrofibers with improved strength and stiffness. However, nearly all of them have been achieved at the expense of elongation and toughness, because strength and toughness are always mutually exclusive for man-made structural materials. Therefore, this dilemma is quite common for previously reported cellulose-based macrofibers, which greatly limited their practical applications.

In a new article published in the National Science Review, Recently, a bionics research team led by Prof. Yu Shuhong from the University of Science and Technology of China (USTC) sought an inspiration to solve this problem from biological structures. …

A July 31, 2019 Science China Press news release on EurekAlert, which originated the news item, provides a few moretechnical details,

… They found that the widespread biosynthesized fibers, such as some plant fibers, spider silk and animal hairs, all have some similar features. They are both strong and tough, and have hierarchical helical structures across multiple length scales with stiff and strong nanoscale fibrous building blocks embedded in soft and energy dissipating matrices.

Inspired by these structural features in biosynthesized fibers, they presented a design strategy to make nanocellulose-based macrofibers with similar structural features. They used bacterial cellulose nanofibers as the strong and stiff building blocks, sodium alginate as the soft matrix. By combining a facile wet-spinning process with a subsequent multiple wet-twisting procedure, they successfully obtained biomimetic hierarchical helical nanocomposite macrofibers, and realized impressive improvement of their tensile strength, elongation and toughness simultaneously as expected.

This achievement certifies the validity of their bioinspired design and provides a potential route for further creating many other strong and tough nanocomposite fiber materials for diverse applications.

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

Bioinspired hierarchical helical nanocomposite macrofibers based on bacterial cellulose nanofibers by Huai-Ling Gao, Ran Zhao, Chen Cui, Yin-Bo Zhu, Si-Ming Chen, Zhao Pan, Yu-Feng Meng, Shao-Meng Wen, Chuang Liu, Heng-An Wu, Shu-Hong Yu. National Science Review, nwz077, https://doi.org/10.1093/nsr/nwz077 Published: 21 June 2019

This paper appears to be open access.

Beautiful solar cells based on insect eyes

What a gorgeous image!

The compound eye of a fly inspired Stanford researchers to create a compound solar cell consisting of perovskite microcells encapsulated in a hexagon-shaped scaffold. (Image credit: Thomas Shahan/Creative Commons)

An August 31, 2017 news item on Nanowerk describes research into solar cells being performed at Stanford University (Note: A link has been removed),

Packing tiny solar cells together, like micro-lenses in the compound eye of an insect, could pave the way to a new generation of advanced photovoltaics, say Stanford University scientists.

In a new study, the Stanford team used the insect-inspired design to protect a fragile photovoltaic material called perovskite from deteriorating when exposed to heat, moisture or mechanical stress. The results are published in the journal Energy & Environmental Science (“Scaffold-reinforced perovskite compound solar cells”).

An August 31, 2017 Stanford University news release (also on EurekAlert) by Mark Schwartz, which originated the news item,

“Perovskites are promising, low-cost materials that convert sunlight to electricity as efficiently as conventional solar cells made of silicon,” said Reinhold Dauskardt, a professor of materials science and engineering and senior author of the study. “The problem is that perovskites are extremely unstable and mechanically fragile. They would barely survive the manufacturing process, let alone be durable long term in the environment.”

Most solar devices, like rooftop panels, use a flat, or planar, design. But that approach doesn’t work well with perovskite solar cells.

“Perovskites are the most fragile materials ever tested in the history of our lab,” said graduate student Nicholas Rolston, a co-lead author of the E&ES study. “This fragility is related to the brittle, salt-like crystal structure of perovskite, which has mechanical properties similar to table salt.”

Eye of the fly

To address the durability challenge, the Stanford team turned to nature.

“We were inspired by the compound eye of the fly, which consists of hundreds of tiny segmented eyes,” Dauskardt explained. “It has a beautiful honeycomb shape with built-in redundancy: If you lose one segment, hundreds of others will operate. Each segment is very fragile, but it’s shielded by a scaffold wall around it.”

Scaffolds in a compound solar cell filled with perovskite after fracture testing.

Scaffolds in a compound solar cell filled with perovskite after fracture testing. (Image credit: Dauskardt Lab/Stanford University)

Using the compound eye as a model, the researchers created a compound solar cell consisting of a vast honeycomb of perovskite microcells, each encapsulated in a hexagon-shaped scaffold just 0.02 inches (500 microns) wide.

“The scaffold is made of an inexpensive epoxy resin widely used in the microelectronics industry,” Rolston said. “It’s resilient to mechanical stresses and thus far more resistant to fracture.”

Tests conducted during the study revealed that the scaffolding had little effect on how efficiently perovskite converted light into electricity.

“We got nearly the same power-conversion efficiencies out of each little perovskite cell that we would get from a planar solar cell,” Dauskardt said. “So we achieved a huge increase in fracture resistance with no penalty for efficiency.”


But could the new device withstand the kind of heat and humidity that conventional rooftop solar panels endure?

To find out, the researchers exposed encapsulated perovskite cells to temperatures of 185 F (85 C) and 85 percent relative humidity for six weeks. Despite these extreme conditions, the cells continued to generate electricity at relatively high rates of efficiency.

Dauskardt and his colleagues have filed a provisional patent for the new technology. To improve efficiency, they are studying new ways to scatter light from the scaffold into the perovskite core of each cell.

“We are very excited about these results,” he said. “It’s a new way of thinking about designing solar cells. These scaffold cells also look really cool, so there are some interesting aesthetic possibilities for real-world applications.”

Researchers have also made this image available,

Caption: A compound solar cell illuminated from a light source below. Hexagonal scaffolds are visible in the regions coated by a silver electrode. The new solar cell design could help scientists overcome a major roadblock to the development of perovskite photovoltaics. Credit: Dauskardt Lab/Stanford University

Not quite as weirdly beautiful as the insect eyes.

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

Scaffold-reinforced perovskite compound solar cells by Brian L. Watson, Nicholas Rolston, Adam D. Printz, and Reinhold H. Dauskardt. Energy & Environmental Science 2017 DOI: 10.1039/C7EE02185B first published on 23 Aug 2017

This paper is behind a paywall.

Dr. Wei Lu and bio-inspired ‘memristor’ chips

It’s been a while since I’ve featured Dr. Wei Lu’s work here. This April  15, 2010 posting features Lu’s most relevant previous work.) Here’s his latest ‘memristor’ work , from a May 22, 2017 news item on Nanowerk (Note: A link has been removed),

Inspired by how mammals see, a new “memristor” computer circuit prototype at the University of Michigan has the potential to process complex data, such as images and video orders of magnitude, faster and with much less power than today’s most advanced systems.

Faster image processing could have big implications for autonomous systems such as self-driving cars, says Wei Lu, U-M professor of electrical engineering and computer science. Lu is lead author of a paper on the work published in the current issue of Nature Nanotechnology (“Sparse coding with memristor networks”).

Lu’s next-generation computer components use pattern recognition to shortcut the energy-intensive process conventional systems use to dissect images. In this new work, he and his colleagues demonstrate an algorithm that relies on a technique called “sparse coding” to coax their 32-by-32 array of memristors to efficiently analyze and recreate several photos.

A May 22, 2017 University of Michigan news release (also on EurekAlert), which originated the news item, provides more information about memristors and about the research,

Memristors are electrical resistors with memory—advanced electronic devices that regulate current based on the history of the voltages applied to them. They can store and process data simultaneously, which makes them a lot more efficient than traditional systems. In a conventional computer, logic and memory functions are located at different parts of the circuit.

“The tasks we ask of today’s computers have grown in complexity,” Lu said. “In this ‘big data’ era, computers require costly, constant and slow communications between their processor and memory to retrieve large amounts data. This makes them large, expensive and power-hungry.”

But like neural networks in a biological brain, networks of memristors can perform many operations at the same time, without having to move data around. As a result, they could enable new platforms that process a vast number of signals in parallel and are capable of advanced machine learning. Memristors are good candidates for deep neural networks, a branch of machine learning, which trains computers to execute processes without being explicitly programmed to do so.

“We need our next-generation electronics to be able to quickly process complex data in a dynamic environment. You can’t just write a program to do that. Sometimes you don’t even have a pre-defined task,” Lu said. “To make our systems smarter, we need to find ways for them to process a lot of data more efficiently. Our approach to accomplish that is inspired by neuroscience.”

A mammal’s brain is able to generate sweeping, split-second impressions of what the eyes take in. One reason is because they can quickly recognize different arrangements of shapes. Humans do this using only a limited number of neurons that become active, Lu says. Both neuroscientists and computer scientists call the process “sparse coding.”

“When we take a look at a chair we will recognize it because its characteristics correspond to our stored mental picture of a chair,” Lu said. “Although not all chairs are the same and some may differ from a mental prototype that serves as a standard, each chair retains some of the key characteristics necessary for easy recognition. Basically, the object is correctly recognized the moment it is properly classified—when ‘stored’ in the appropriate category in our heads.”

Image of a memristor chip Image of a memristor chip Similarly, Lu’s electronic system is designed to detect the patterns very efficiently—and to use as few features as possible to describe the original input.

In our brains, different neurons recognize different patterns, Lu says.

“When we see an image, the neurons that recognize it will become more active,” he said. “The neurons will also compete with each other to naturally create an efficient representation. We’re implementing this approach in our electronic system.”

The researchers trained their system to learn a “dictionary” of images. Trained on a set of grayscale image patterns, their memristor network was able to reconstruct images of famous paintings and photos and other test patterns.

If their system can be scaled up, they expect to be able to process and analyze video in real time in a compact system that can be directly integrated with sensors or cameras.

The project is titled “Sparse Adaptive Local Learning for Sensing and Analytics.” Other collaborators are Zhengya Zhang and Michael Flynn of the U-M Department of Electrical Engineering and Computer Science, Garrett Kenyon of the Los Alamos National Lab and Christof Teuscher of Portland State University.

The work is part of a $6.9 million Unconventional Processing of Signals for Intelligent Data Exploitation project that aims to build a computer chip based on self-organizing, adaptive neural networks. It is funded by the [US] Defense Advanced Research Projects Agency [DARPA].

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

Sparse coding with memristor networks by Patrick M. Sheridan, Fuxi Cai, Chao Du, Wen Ma, Zhengya Zhang, & Wei D. Lu. Nature Nanotechnology (2017) doi:10.1038/nnano.2017.83 Published online 22 May 2017

This paper is behind a paywall.

For the interested, there are a number of postings featuring memristors here (just use ‘memristor’ as your search term in the blog search engine). You might also want to check out ‘neuromorphic engineeering’ and ‘neuromorphic computing’ and ‘artificial brain’.

A nano fabrication technique used to create next generation heart valve

I am going to have take the researchers’ word that these somehow lead to healthy heart valve tissue,

In rotary jet spinning technology, a rotating nozzle extrudes a solution of extracellular matrix (ECM) into nanofibers that wrap themselves around heart valve-shaped mandrels. By using a series of mandrels with different sizes, the manufacturing process becomes fully scalable and is able to provide JetValves for all age groups and heart sizes. Credit: Wyss Institute at Harvard University

From a May 18, 2017 news item on ScienceDaily,

The human heart beats approximately 35 million times every year, effectively pumping blood into the circulation via four different heart valves. Unfortunately, in over four million people each year, these delicate tissues malfunction due to birth defects, age-related deteriorations, and infections, causing cardiac valve disease.

Today, clinicians use either artificial prostheses or fixed animal and cadaver-sourced tissues to replace defective valves. While these prostheses can restore the function of the heart for a while, they are associated with adverse comorbidity and wear down and need to be replaced during invasive and expensive surgeries. Moreover, in children, implanted heart valve prostheses need to be replaced even more often as they cannot grow with the child.

A team lead by Kevin Kit Parker, Ph.D. at Harvard University’s Wyss Institute for Biologically Inspired Engineering recently developed a nanofiber fabrication technique to rapidly manufacture heart valves with regenerative and growth potential. In a paper published in Biomaterials, Andrew Capulli, Ph.D. and colleagues fabricated a valve-shaped nanofiber network that mimics the mechanical and chemical properties of the native valve extracellular matrix (ECM). To achieve this, the team used the Parker lab’s proprietary rotary jet spinning technology — in which a rotating nozzle extrudes an ECM solution into nanofibers that wrap themselves around heart valve-shaped mandrels. “Our setup is like a very fast cotton candy machine that can spin a range of synthetic and natural occurring materials. In this study, we used a combination of synthetic polymers and ECM proteins to fabricate biocompatible JetValves that are hemodynamically competent upon implantation and support cell migration and re-population in vitro. Importantly, we can make human-sized JetValves in minutes — much faster than possible for other regenerative prostheses,” said Parker.

A May 18,2017 Wyss Institute for Biologically Inspired Engineering news release (also on EurekAlert), which originated the news item, expands on the theme of Jetvalves,

To further develop and test the clinical potential of JetValves, Parker’s team collaborated with the translational team of Simon P. Hoerstrup, M.D., Ph.D., at the University of Zurich in Switzerland, which is a partner institution with the Wyss Institute. As a leader in regenerative heart prostheses, Hoerstrup and his team in Zurich have previously developed regenerative, tissue-engineered heart valves to replace mechanical and fixed-tissue heart valves. In Hoerstrup’s approach, human cells directly deposit a regenerative layer of complex ECM on biodegradable scaffolds shaped as heart valves and vessels. The living cells are then eliminated from the scaffolds resulting in an “off-the-shelf” human matrix-based prostheses ready for implantation.

In the paper, the cross-disciplinary team successfully implanted JetValves in sheep using a minimally invasive technique and demonstrated that the valves functioned properly in the circulation and regenerated new tissue. “In our previous studies, the cell-derived ECM-coated scaffolds could recruit cells from the receiving animal’s heart and support cell proliferation, matrix remodeling, tissue regeneration, and even animal growth. While these valves are safe and effective, their manufacturing remains complex and expensive as human cells must be cultured for a long time under heavily regulated conditions. The JetValve’s much faster manufacturing process can be a game-changer in this respect. If we can replicate these results in humans, this technology could have invaluable benefits in minimizing the number of pediatric re-operations,” said Hoerstrup.

In support of these translational efforts, the Wyss Institute for Biologically Inspired Engineering and the University of Zurich announced today a cross-institutional team effort to generate a functional heart valve replacement with the capacity for repair, regeneration, and growth. The team is also working towards a GMP-grade version of their customizable, scalable, and cost-effective manufacturing process that would enable deployment to a large patient population. In addition, the new heart valve would be compatible with minimally invasive procedures to serve both pediatric and adult patients.

The project will be led jointly by Parker and Hoerstrup. Parker is a Core Faculty member of the Wyss Institute and the Tarr Family Professor of Bioengineering and Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). Hoerstrup is Chair and Director of the University of Zurich’s Institute for Regenerative Medicine (IREM), Co-Director of the recently founded Wyss Translational Center Zurich and a Wyss Institute Associate Faculty member.

Since JetValves can be manufactured in all desired shapes and sizes, and take seconds to minutes to produce, the team’s goal is to provide customized, ready-to-use, regenerative heart valves much faster and at much lower cost than currently possible.

“Achieving the goal of minimally invasive, low-cost regenerating heart valves could have tremendous impact on patients’ lives across age-, social- and geographical boundaries. Once again, our collaborative team structure that combines unique and leading expertise in bioengineering, regenerative medicine, surgical innovation and business development across the Wyss Institute and our partner institutions, makes it possible for us to advance technology development in ways not possible in a conventional academic laboratory,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and the Vascular Biology Program at Boston Children’s Hospital, as well as Professor of Bioengineering at SEAS.

This scanning electron microscopy image shows how extracellular matrix (ECM) nanofibers generated with JetValve technology are arranged in parallel networks with physical properties comparable to those found in native heart tissue. Credit: Wyss Institute at Harvard University

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

JetValve: Rapid manufacturing of biohybrid scaffolds for biomimetic heart valve replacement by Andrew K. Capulli, Maximillian Y. Emmert, Francesco S. Pasqualini, b, Debora Kehl, Etem Caliskan, Johan U. Lind, Sean P. Sheehy, Sung Jin Park, Seungkuk Ahn, Benedikt Webe, Josue A. Goss. Biomaterials Volume 133, July 2017, Pages 229–241  https://doi.org/10.1016/j.biomaterials.2017.04.033

This paper is behind a paywall.

The inside scoop on beetle exoskeletons

In the past I’ve covered work on the Namib beetle and its bumps which allow it to access condensation from the air in one of the hottest places on earth and work on jewel beetles and how their structural colo(u)r is derived. Now, there’s research into a beetle’s body armor from the University of Nebraska-Lincoln according to a Feb. 22, 2017 news item on ScienceDaily,

Beetles wear a body armor that should weigh them down — think medieval knights and turtles. In fact, those hard shells protecting delicate wings are surprisingly light, allowing even flight.

Better understanding the structure and properties of beetle exoskeletons could help scientists engineer lighter, stronger materials. Such materials could, for example, reduce gas-guzzling drag in vehicles and airplanes and reduce the weight of armor, lightening the load for the 21st-century knight.

But revealing exoskeleton architecture at the nanoscale has proven difficult. Nebraska’s Ruiguo Yang, assistant professor of mechanical and materials engineering, and his colleagues found a way to analyze the fibrous nanostructure. …

A Feb. 22, 2017 University of Nebraska-Lincoln news release by Gillian Klucas (also on EurekAlert), which originated the news item, describes skeletons and the work in more detail,

The lightweight exoskeleton is composed of chitin fibers just around 20 nanometers in diameter (a human hair measures approximately 75,000 nanometers in diameter) and packed and piled into layers that twist in a spiral, like a spiral staircase. The small diameter and helical twisting, known as Bouligand, make the structure difficult to analyze.

Yang and his team developed a method of slicing down the spiral to reveal a surface of cross-sections of fibers at different orientations. From that viewpoint, the researchers were able to analyze the fibers’ mechanical properties with the aid of an atomic force microscope. This type of microscope applies a tiny force to a test sample, deforms the sample and monitors the sample’s response. Combining the experimental procedure and theoretical analysis, the researchers were able to reveal the nanoscale architecture of the exoskeleton and the material properties of the nanofibers.

Yang holds a piece of the atomic force microscope used to measure the beetle's surface. A small wire can barely be seen in the middle of the piece. Unseen is a two-nano-size probe attached to the wire, which does the actual measuring.

Craig Chandler | University Communication

Yang holds a piece of the atomic force microscope used to measure the beetle’s surface. A small wire can barely be seen in the middle of the piece. Unseen is a two-nano-size probe attached to the wire, which does the actual measuring.

They made their discoveries in the common figeater beetle, Cotinis mutabilis, a metallic green native of the western United States. But the technique can be used on other beetles and hard-shelled creatures and might also extend to artificial materials with fibrous structures, Yang said.

Comparing beetles with differing demands on their exoskeletons, such as defending against predators or environmental damage, could lead to evolutionary insights as well as a better understanding of the relationship between structural features and their properties.

Yang’s co-authors are Alireza Zaheri and Horacio Espinosa of Northwestern University; Wei Gao of the University of Texas at San Antonio; and Cheryl Hayashi of the University of California, Riverside.

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

Exoskeletons: AFM Identification of Beetle Exocuticle: Bouligand Structure and Nanofiber Anisotropic Elastic Properties by Ruiguo Yang, Alireza Zaheri,Wei Gao, Charely Hayashi, Horacio D. Espinosa. Adv. Funct. Mater. vol. 27 (6) 2017 DOI: 10.1002/adfm.201770031 First published: 8 February 2017

This paper is behind a paywall.

Brown recluse spider, one of the world’s most venomous spiders, shows off unique spinning technique

Caption: American Brown Recluse Spider is pictured. Credit: Oxford University

According to scientists from Oxford University this deadly spider could teach us a thing or two about strength. From a Feb. 15, 2017 news item on ScienceDaily,

Brown recluse spiders use a unique micro looping technique to make their threads stronger than that of any other spider, a newly published UK-US collaboration has discovered.

One of the most feared and venomous arachnids in the world, the American brown recluse spider has long been known for its signature necro-toxic venom, as well as its unusual silk. Now, new research offers an explanation for how the spider is able to make its silk uncommonly strong.

Researchers suggest that if applied to synthetic materials, the technique could inspire scientific developments and improve impact absorbing structures used in space travel.

The study, published in the journal Material Horizons, was produced by scientists from Oxford University’s Department of Zoology, together with a team from the Applied Science Department at Virginia’s College of William & Mary. Their surveillance of the brown recluse spider’s spinning behaviour shows how, and to what extent, the spider manages to strengthen the silk it makes.

A Feb. 15, 2017 University of Oxford press release, which originated the news item,  provides more detail about the research,

From observing the arachnid, the team discovered that unlike other spiders, who produce round ribbons of thread, recluse silk is thin and flat. This structural difference is key to the thread’s strength, providing the flexibility needed to prevent premature breakage and withstand the knots created during spinning which give each strand additional strength.

Professor Hannes Schniepp from William & Mary explains: “The theory of knots adding strength is well proven. But adding loops to synthetic filaments always seems to lead to premature fibre failure. Observation of the recluse spider provided the breakthrough solution; unlike all spiders its silk is not round, but a thin, nano-scale flat ribbon. The ribbon shape adds the flexibility needed to prevent premature failure, so that all the microloops can provide additional strength to the strand.”

By using computer simulations to apply this technique to synthetic fibres, the team were able to test and prove that adding even a single loop significantly enhances the strength of the material.

William & Mary PhD student Sean Koebley adds: “We were able to prove that adding even a single loop significantly enhances the toughness of a simple synthetic sticky tape. Our observations open the door to new fibre technology inspired by the brown recluse.”

Speaking on how the recluse’s technique could be applied more broadly in the future, Professor Fritz Vollrath, of the Department of Zoology at Oxford University, expands: “Computer simulations demonstrate that fibres with many loops would be much, much tougher than those without loops. This right away suggests possible applications. For example carbon filaments could be looped to make them less brittle, and thus allow their use in novel impact absorbing structures. One example would be spider-like webs of carbon-filaments floating in outer space, to capture the drifting space debris that endangers astronaut lives’ and satellite integrity.”

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

Toughness-enhancing metastructure in the recluse spider’s looped ribbon silk by
S. R. Koebley, F. Vollrath, and H. C. Schniepp. Mater. Horiz., 2017, Advance Article DOI: 10.1039/C6MH00473C First published online 15 Feb 2017

This paper is open access although you may need to register with the Royal Society of Chemistry’s publishing site to get access.

Effective sunscreens from nature

The dream is to find sunscreens that don’t endanger humans or pollute the environment and it seems that Spanish scientists may have taken a step closer to making that dream a reality (from a Jan. 30, 2017 Wiley Publications press release (also on EurekAlert),

The ideal sunscreen should block UVB and UVA radiation while being safe and stable. In the journal Angewandte Chemie, Spanish scientists have introduced a new family of UVA and UVB filters based on natural sunscreen substances found in algae and cyanobacteria. They are highly stable and enhance the effectivity [sic] of commercial sunscreens.

Good news for sunseekers. Commercial [sic] available sunscreen lotions can very effectively protect from dangerous radiation in the ultraviolet [spectrum], but they need to be applied regularly and in high amounts to develop their full potential. One of the most critical issues is the limited stability of the UV filter molecules. Inspired by nature, Diego Sampedro and his colleagues from La Rioja University in Logrono and collaborators from Malaga University and Alcala University, Madrid, Spain, have screened a natural class of UV-protecting [blocking?] molecules for their possible use in skin protection. They adjusted the nature-given motif [sic] to the requirements of chemical synthesis and found that the molecules could indeed boost the sun protection factor of common formulations.

The natural sunscreen molecules are called microsporine-like amino acids (MAAs) and are widespread in the microbial world, most prominently in marine algae and cyanobacteria. MAAs are small molecules derived from amino acids, thermally stable, and they absorb light in the ultraviolet region, protecting the microbial DNA from radiation damage. Thus they are natural sunscreens, which inspired Sampedro and his colleagues to create [a] new class of organic sunscreen compounds.

Theoretical calculations revealed what is chemically needed for a successful design. “We performed a computer calculation of several basic scaffolds [..] to identify the simplest compound that fulfills the requisites for efficient sunscreens”, the authors write. The result of their search was a set of molecules which were readily synthesized, “avoiding the decorating substituents that come from the biosynthetic route.” Thus the small basic molecules can be tuned to give them more favorable properties.

The authors found that the synthesized compounds are characterized by excellent filter capacities in the relevant UV range. In addition they are photostable, much more than, for example, oxybenzene [sic] which is a widely used sunscreen in commercial formulations. They do not react chemically and dissipate radiation as heat (but not to such an extent that the skin temperature would rise as well). And, most importantly, when tested in real formulations, the sun protection factor (SPF) rose by a factor of more than two. Thus they could be promising targets for more stable, more efficient sunscreen lotions. Good news for your next summer vacation.

There’s some unusual phrasing so, I’m guessing that the writer it not accustomed to writing press releases in English. One other comment, it’s oxybenzone that’s often used as an ingredient in commercial sunscreens.

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

Rational Design and Synthesis of Efficient Sunscreens To Boost the Solar Protection Factor by Raúl Losantos, Ignacio Funes-Ardoiz, Dr. José Aguilera, Prof. Enrique Herrera-Ceballos, Dr. Cristina García-Iriepa, Prof. Pedro J. Campos, and Diego Sampedro. Angewandte Chemie International Edition Volume 56, Issue 10, pages 2632–2635, March 1, 2017 DOI: 10.1002/anie.201611627 Version of Record online: 27 JAN 2017

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

I have previously featured work on another natural sunscreen. In that case it was to be derived from English ivy (July 22, 2010 posting); there was an update on the English ivy work in a May 30, 2016 posting but the researcher has moved in a different direction looking at wound healing and armour as possible applications for the research.

Sea sponges don’t buckle under pressure

You wouldn’t think a sponge (the sea creature) was particularly tough but it is according to a Jan. 4, 2017 news item on Nanowerk,

Judging by their name alone, orange puffball sea sponges might seem unlikely paragons of structural strength. But maintaining their shape at the bottom of the churning ocean is critical to the creatures’ survival, and new research shows that tiny structural rods in their bodies have evolved the optimal shape to avoid buckling under pressure.

The rods, called strongyloxea spicules, measure about 2 millimeters long and are thinner than a human hair. Hundreds of them are bundled together, forming stiff rib-like structures inside the orange puffball’s spongy body. It was the odd and remarkably consistent shape of each spicule that caught the eye of Brown University engineers Haneesh Kesari and Michael Monn. Each one is symmetrically tapered along its length — going gradually from fatter in the middle to thinner at the ends.

Caption: Tiny rods found inside the bodies of orange puffball sea sponges have an interesting tapered shape. That shape, new research shows, turns out to be a match for the Clausen profile, a column shape shown to be optimal for resistance to buckling failure. Credit: Michael Monn, Haneesh Kesari / Brown University

A Jan. 4, 2017 Brown University news release on EurekAlert, which originated the news item, describes the research in more detail,

Using structural mechanics models and a bit of digging in obscure mathematics journals, Monn and Kesari showed the peculiar shape of the spicules to be optimal for resistance to buckling, the primary mode of failure for slender structures. This natural shape could provide a blueprint for increasing the buckling resistance in all kinds of slender human-made structures, from building columns to bicycle spokes to arterial stents, the researchers say.

“This is one of the rare examples that we’re aware of where a natural structure is not just well-suited for a given function, but actually approaches a theoretical optimum,” said Kesari, an assistant professor of engineering at Brown. “There’s no engineering analog for this shape — we don’t see any columns or other slender structures that are tapered in this way. So in this case, nature has shown us something quite new that we think could be useful in engineering.”

The findings are published in the journal Scientific Reports.

Function and form

Orange puffball sponges (Tethya aurantia) are native to the Mediterranean Sea. They live mainly in rocky coastal environments, where they’re subject to the constant stress of underwater waves and tidal forces. Sponges are filter feeders — they pump water through their bodies to extract nutrients and oxygen. To do this, their bodies need to be porous and compliant, but they also need enough stiffness to avoid being deformed too much.

“If you compress them too much, you’re essentially choking them,” Kesari said. “So maintaining their stiffness is critical to their survival.”

And that means the spicules, which make up the rib-like structures that give sponges their stiffness, are critical components. When Monn and Kesari saw the shapes of the spicules under a microscope, the consistency of the tapered shape from spicule to spicule was hard to miss.

“We saw the shape and wondered if there might be an engineering principle at work here,” Kesari said.

To figure that out, the researchers first needed to understand what forces were acting on each individual spicule. So Monn and Kesari developed a structural mechanics model of spicules bundled within a sponge’s ribs. The model showed that the mismatch in stiffness between the bulk of the sponge’s soft body and the more rigid spicules causes each spicule to experience primarily one type of mechanical loading — a compression load on each of its ends.

“You can imagine taking a toothpick and trying to squeeze it longways between your fingers,” Monn said. “That’s how these spicules see the world.”

The primary mode of failure for a structure with this mechanical load is through buckling. At a certain critical load, the structure starts to bend somewhere along its length. Once the bending starts, the force transferred by the load is amplified at the bending point, which causes the structure to break or collapse.

Once Kesari and Monn knew what forces were acting on the spicules and how they would fail, the next step was looking to see if there was anything special about them that helped them resist buckling. Scanning electron microscope images of the inside of a spicule and other tests showed that they were monolithic silica — essentially glass.

“We could see that there was no funny business going on with the material properties,” Monn said. “If there was anything contributing to its mechanical performance, it would have to be the shape.”

Optimal shape

Kesari and Monn combed the literature to see if they could find anything on tapering in slender structures. They came up empty in the modern engineering literature. But they found something interesting published more than 150 years ago by a German scientist named Thomas Clausen.

In 1851, Clausen proposed that columns that are tapered toward their ends should have more buckling resistance than plain cylinders, which had been and still are the primary design for architectural columns. In the 1960s, mathematician Joseph Keller published an ironclad mathematical proof that the Clausen column was indeed optimal for resistance to buckling — having 33 percent better resistance than a cylinder. Even compared to a very similar shape — an ellipse, which is slightly fatter in the middle and pointier at the ends — the Clausen column had 18 percent better buckling resistance.

Knowing what the optimal column shape is, Monn and Kesari started making precise dimensional measurements of dozens of spicules. They showed that their shapes were remarkably consistent and nearly identical to that of the Clausen column.

“The spicules were a match for the best shape of all possible column shapes,” Monn said.

It seems in this case, natural selection figured out something that engineers have not. Despite the fact that it’s been mathematically shown to be the optimal column shape, the Clausen profile isn’t widely known in the engineering community. Kesari and Monn hope this work might bring it out of the shadows.

“We see this as an addition to our library of structural designs,” Monn said. “We’re not just talking about an improvement of a few percent. This shape is 33 percent better than the cylinder, which is quite an improvement.”

In particular, the shape would be particularly useful in a new generation of materials made from nanoscale truss structures. “It would be easy to 3-D print the Clausen profile into these materials, and you’d get a tremendous increase in buckling resistance, which is often how these materials fail.”

Lessons from nature

The field of bio-inspired engineering began at a time when many people viewed adaptive evolution as an unceasing march toward perfection. If that were true, scientists should find untold numbers of optimal structures in nature.

But the modern understanding of evolution is a bit different. It’s now understood that in order for a trait to be conserved by natural selection, it doesn’t need to be optimal. It just needs to be good enough to work. That has put a bit of a damper on the enthusiasm for bio-inspired engineering, Kesari and Monn say.

However, they say, this work shows that nearly optimal structures are out there if researchers look in the right places. In this case, they looked at creatures from a very old phylum — sea sponges are among the very first animals on Earth — with plenty of time to evolve under consistent selection pressures.

Sponges are also fairly simple creatures, so understanding the function of a given trait is relatively straightforward. In this case, the spicule appears to have one and only one job to do — provide stiffness. Compare that to, for example, human bone, which not only provides support but must also accommodate arteries, provide attachment points for muscles and house bone marrow. Those other functions may cause tradeoffs in adaptations for strength or stiffness.

“With the sponges, you have lots of evolutionary pressure, lots of time and opportunity to respond to that pressure, and functional elements that can be easily identified,” Kesari said.

With those as guiding principles, there may well be more ideal structures out there waiting to be found.

“This work shows that nature can hit an optimum,” Kesari said, “and the biological world can still be hiding completely new designs of considerable technological significance in plain sight.”

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

A new structure-property connection in the skeletal elements of the marine sponge Tethya aurantia that guards against buckling instability by Michael A. Monn & Haneesh Kesari. Scientific Reports 7, Article number: 39547 (2017) doi:10.1038/srep39547 Published online: 04 January 2017

This paper is open access.

Kesari and Monn have researched sea sponges previously as can be seen in my April 7, 2015 posting, which highlights their work on strength and Venus’ flower basket sea sponge.