Category Archives: biomimcry

Oil-absorbing hairy fern leaves lead to ‘nanofur’ for oil spill cleanups

German researchers have developed a biomimetic material branded as ‘nanofur’ for oil spill cleanups, according to an Aug. 23, 2016 news item on Nanowerk (Note: A link has been removed),

Some water ferns can absorb large volumes of oil within a short time, because their leaves are strongly water-repellent and, at the same time, highly oil-absorbing. Researchers of Karlsruhe Institute of Technology, together with colleagues of Bonn University, have found that the oil-binding capacity of the water plant results from the hairy microstructure of its leaves (Bioinspiration & Biomimetics, “Microstructures of superhydrophobic plant leaves – inspiration for efficient oil spill cleanup materials”). It is now used as a model to further develop the new Nanofur material for the environmentally friendly cleanup of oil spills.

An Aug.(?) 23 (?), 2016 Karlsruhe Institute of Technology (KIT) press release on EurekAlert, which originated the news item, explains the interest in improving technology for oil spill cleanups and provides insight into this  innovation,

Damaged pipelines, oil tanker disasters, and accidents on oil drilling and production platforms may result in pollutions [sic] of water with crude or mineral oil. Conventional methods to clean up the oil spill are associated with specific drawbacks. Oil combustion or the use of chemical substances to accelerate oil decomposition cause secondary environmental pollution. Many natural materials to take up the oil, such as sawdust or plant fibers, are hardly effective, because they also absorb large amounts of water. On their search for an environmentally friendly alternative to clean up oil spills, the researchers compared various species of aquatic ferns. “We already knew that the leaves of these plants repel water, but for the first time now, we have studied their capacity to absorb oil,” Claudia Zeiger says. She conducted the project at KIT’s Institute of Microstructure Technology.

Damaged pipelines, oil tanker disasters, and accidents on oil drilling and production platforms may result in pollutions of water with crude or mineral oil. Conventional methods to clean up the oil spill are associated with specific drawbacks. Oil combustion or the use of chemical substances to accelerate oil decomposition cause secondary environmental pollution. Many natural materials to take up the oil, such as sawdust or plant fibers, are hardly effective, because they also absorb large amounts of water. On their search for an environmentally friendly alternative to clean up oil spills, the researchers compared various species of aquatic ferns. “We already knew that the leaves of these plants repel water, but for the first time now, we have studied their capacity to absorb oil,” Claudia Zeiger says. She conducted the project at KIT’s Institute of Microstructure Technology.

Aquatic ferns originally growing in tropical and subtropical regions can now also be found in parts of Europe. As they reproduce strongly, they are often considered weed. However, they have a considerable potential as low-cost, rapid, and environmentally friendly oil absorbers, which is obvious from a short video (see below). ”The plants might be used in lakes to absorb accidental oil spills,” Zeiger says. After less than 30 seconds, the leaves reach maximum absorption and can be skimmed off together with the absorbed oil. The water plant named salvinia has trichomes on the leaf surface – hairy extensions of 0.3 to 2.5 mm in length. Comparison of different salvinia species revealed that leaves with the longest hairs did not absorb the largest amounts of oil. “Oil-absorbing capacity is determined by the shape of the hair ends,” Zeiger emphasizes. The largest quantity of oil was absorbed by leaves of the water fern salvinia molesta, whose hair ends are shaped like an eggbeater.

Based on this new knowledge on the relationship between surface structure of leaves and their oil-absorbing capacity, the researchers improved the ‘Nanofur’ material developed at their institute. This plastic nanofur mimics the water-repellent and oil-absorbing effect of salvinia to separate oil and water. “We study nanostructures and microstructures in nature for potential technical developments,” says Hendrik Hölscher, Head of the Biomimetic Surfaces Group of the Institute of Microstructure Technology of KIT. He points out that different properties of plants made of the same material frequently result from differences of their finest structures.

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

Microstructures of superhydrophobic plant leaves – inspiration for efficient oil spill cleanup materials by Claudia Zeiger, Isabelle C Rodrigues da Silva, Matthias Mail, Maryna N Kavalenka, Wilhelm Barthlott, and Hendrik Hölscher. Bioinspiration & Biomimetics, Volume 11, Number 5 DOI: http://dx.doi.org/10.1088/1748-3190/11/5/056003

Published 16 August 2016, © 2016 IOP Publishing Ltd

This article appears to be open access.

There is also a video demonstration of the material,

Enjoy!

Spider silk as a bio super-lens

Bangor University (Wales, UK) is making quite the impact these days. I’d never heard of the institution until their breakthrough with nanobeads (Sept. 7, 2016 posting) to break through a resolution barrier and now there’s a second breakthrough with their partners at Oxford University (England, UK). From an Aug. 19, 2016 news item on ScienceDaily (Note: A link has been removed),

Scientists at the UK’s Bangor and Oxford universities have achieved a world first: using spider-silk as a superlens to increase the microscope’s potential.

Extending the limit of classical microscope’s resolution has been the ‘El Dorado’ or ‘Holy Grail’ of microscopy for over a century. Physical laws of light make it impossible to view objects smaller than 200 nm — the smallest size of bacteria, using a normal microscope alone. However, superlenses which enable us to see beyond the current magnification have been the goal since the turn of the millennium.

Hot on the heels of a paper (Sci. Adv. 2 e1600901,2016) revealing that a team at Bangor University’s School of Electronic Engineering has used a nanobead-derived superlens to break the perceived resolution barrier, the same team has achieved another world first.

Now the team, led by Dr Zengbo Wang and in colloboration with Prof. Fritz Vollrath’s silk group at Oxford University’s Department of Zoology, has used a naturally occurring material — dragline silk of the golden web spider, as an additional superlens, applied to the surface of the material to be viewed, to provide an additional 2-3 times magnification.

This is the first time that a naturally occurring biological material has been used as a superlens.

An Aug. 19, 2016 Bangor University press release (also on EurekAlert), which originated the news item, provides more information about the new work,

In the paper in Nano Letters (DOI: 10.1021/acs.nanolett.6b02641, Aug 17 2016), the joint team reveals how they used a cylindrical piece of spider silk from the thumb sized Nephila spider as a lens.

Dr Zengbo Wang said:

“We have proved that the resolution barrier of microscope can be broken using a superlens, but production of manufactured superlenses invovles some complex engineering processes which are not widely accessible to other reserchers. This is why we have been interested in looking for naturally occurring superlenses provided by ‘Mother Nature’, which may exist around us, so that everyone can access superlenses.”

Prof Fritz Vollrath adds:

“It is very exciting to find yet another cutting edge and totally novel use for a spider silk, which we have been studying for over two decades in my laboratory.”

These lenses could be used for seeing and viewing previously ‘invisible’ structures, including engineered nano-structures and biological micro-structures as well as, potentially, native germs and viruses.

The natural cylindrical structure at a micron- and submicron-scale make silks ideal candidates, in this case, the individual filaments had diameters of one tenth of a thin human hair.

The spider filament enabled the group to view details on a micro-chip and a blue- ray disk which would be invisible using the unmodified optical microscope.

In much the same was as when you look through a cylindrical glass or bottle, the clearest image only runs along the narrow strip directly opposite your line of vision, or resting on the surface being viewed, the single filament provides a one dimensional viewing image along its length.

Wang explains:

“The cylindrical silk lens has advantages in the larger field-of-view when compared to a microsphere superlens. Importantly for potential commercial applications, a spider silk nanoscope would be robust and economical, which in turn could provide excellent manufacturing platforms for a wide range of applications.”

James Monks, a co-author on the paper comments: “it has been an exciting time to be able to develop this project as part of my honours degree in electronic engineering at Bangor University and I am now very much looking forward to joining Dr Wang’s team as a PhD student in nano-photonics.”

The researchers have provided a close up image with details,

Caption: (a) Nephila edulis spider in its web. (b) Schematic drawing of reflection mode silk biosuperlens imaging. The spider silk was placed directly on top of the sample surface by using a soft tape, which magnify underlying nano objects 2-3 times (c) SEM image of Blu-ray disk with 200/100 nm groove and lines (d) Clear magnified image (2.1x) of Blu-ray disk under spider silk superlens. Credit: Bangor University/ University of Oxford

Caption: (a) Nephila edulis spider in its web. (b) Schematic drawing of reflection mode silk biosuperlens imaging. The spider silk was placed directly on top of the sample surface by using a soft tape, which magnify underlying nano objects 2-3 times (c) SEM image of Blu-ray disk with 200/100 nm groove and lines (d) Clear magnified image (2.1x) of Blu-ray disk under spider silk superlens. Credit: Bangor University/ University of Oxford

Here’s a link to and a citation for the ‘spider silk’ superlens paper,

Spider Silk: Mother Nature’s Bio-Superlens by James N. Monks, Bing Yan, Nicholas Hawkins, Fritz Vollrath, and Zengbo Wang. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.6b02641 Publication Date (Web): August 17, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Graphene ribbons in solution bending and twisting like DNA

An Aug. 15, 2016 news item on ScienceDaily announces research into graphene nanoribbons and their DNA (deoxyribonucleic acid)-like properties,

Graphene nanoribbons (GNRs) bend and twist easily in solution, making them adaptable for biological uses like DNA analysis, drug delivery and biomimetic applications, according to scientists at Rice University.

Knowing the details of how GNRs behave in a solution will help make them suitable for wide use in biomimetics, according to Rice physicist Ching-Hwa Kiang, whose lab employed its unique capabilities to probe nanoscale materials like cells and proteins in wet environments. Biomimetic materials are those that imitate the forms and properties of natural materials.

An Aug. 15, 2016 Rice University (Texas, US) news release (also on EurekAlert), which originated the news item, describes the ribbons and the research in more detail,

Graphene nanoribbons can be thousands of times longer than they are wide. They can be produced in bulk by chemically “unzipping” carbon nanotubes, a process invented by Rice chemist and co-author James Tour and his lab.

Their size means they can operate on the scale of biological components like proteins and DNA, Kiang said. “We study the mechanical properties of all different kinds of materials, from proteins to cells, but a little different from the way other people do,” she said. “We like to see how materials behave in solution, because that’s where biological things are.” Kiang is a pioneer in developing methods to probe the energy states of proteins as they fold and unfold.

She said Tour suggested her lab have a look at the mechanical properties of GNRs. “It’s a little extra work to study these things in solution rather than dry, but that’s our specialty,” she said.

Nanoribbons are known for adding strength but not weight to solid-state composites, like bicycle frames and tennis rackets, and forming an electrically active matrix. A recent Rice project infused them into an efficient de-icer coating for aircraft.

But in a squishier environment, their ability to conform to surfaces, carry current and strengthen composites could also be valuable.

“It turns out that graphene behaves reasonably well, somewhat similar to other biological materials. But the interesting part is that it behaves differently in a solution than it does in air,” she said. The researchers found that like DNA and proteins, nanoribbons in solution naturally form folds and loops, but can also form helicoids, wrinkles and spirals.

Kiang, Wijeratne [Sithara Wijeratne, Rice graduate now a postdoctoral researcher at Harvard University] and Jingqiang Li, a co-author and student in the Kiang lab, used atomic force microscopy to test their properties. Atomic force microscopy can not only gather high-resolution images but also take sensitive force measurements of nanomaterials by pulling on them. The researchers probed GNRs and their precursors, graphene oxide nanoribbons.

The researchers discovered that all nanoribbons become rigid under stress, but their rigidity increases as oxide molecules are removed to turn graphene oxide nanoribbons into GNRs. They suggested this ability to tune their rigidity should help with the design and fabrication of GNR-biomimetic interfaces.

“Graphene and graphene oxide materials can be functionalized (or modified) to integrate with various biological systems, such as DNA, protein and even cells,” Kiang said. “These have been realized in biological devices, biomolecule detection and molecular medicine. The sensitivity of graphene bio-devices can be improved by using narrow graphene materials like nanoribbons.”

Wijeratne noted graphene nanoribbons are already being tested for use in DNA sequencing, in which strands of DNA are pulled through a nanopore in an electrified material. The base components of DNA affect the electric field, which can be read to identify the bases.

The researchers saw nanoribbons’ biocompatibility as potentially useful for sensors that could travel through the body and report on what they find, not unlike the Tour lab’s nanoreporters that retrieve information from oil wells.

Further studies will focus on the effect of the nanoribbons’ width, which range from 10 to 100 nanometers, on their properties.

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

Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution by Sithara S. Wijeratne, Evgeni S. Penev, Wei Lu, Jingqiang Li, Amanda L. Duque, Boris I. Yakobson, James M. Tour, & Ching-Hwa Kiang. Scientific Reports 6, Article number: 31174 (2016)  doi:10.1038/srep31174 Published online: 09 August 2016

This paper is open access.

Robots built from living tissue

Biohybrid robots, as they are known, are built from living tissue but not in a Frankenstein kind of way as Victoria Webster PhD candidate at Case Western Reserve University (US) explains in her Aug. 9, 2016 essay on The Conversation (also on phys.org as an Aug. 10, 2016 news item; Note: Links have been removed),

Researchers are increasingly looking for solutions to make robots softer or more compliant – less like rigid machines, more like animals. With traditional actuators – such as motors – this can mean using air muscles or adding springs in parallel with motors. …

But there’s a growing area of research that’s taking a different approach. By combining robotics with tissue engineering, we’re starting to build robots powered by living muscle tissue or cells. These devices can be stimulated electrically or with light to make the cells contract to bend their skeletons, causing the robot to swim or crawl. The resulting biobots can move around and are soft like animals. They’re safer around people and typically less harmful to the environment they work in than a traditional robot might be. And since, like animals, they need nutrients to power their muscles, not batteries, biohybrid robots tend to be lighter too.

Webster explains how these biobots are built,

Researchers fabricate biobots by growing living cells, usually from heart or skeletal muscle of rats or chickens, on scaffolds that are nontoxic to the cells. If the substrate is a polymer, the device created is a biohybrid robot – a hybrid between natural and human-made materials.

If you just place cells on a molded skeleton without any guidance, they wind up in random orientations. That means when researchers apply electricity to make them move, the cells’ contraction forces will be applied in all directions, making the device inefficient at best.

So to better harness the cells’ power, researchers turn to micropatterning. We stamp or print microscale lines on the skeleton made of substances that the cells prefer to attach to. These lines guide the cells so that as they grow, they align along the printed pattern. With the cells all lined up, researchers can direct how their contraction force is applied to the substrate. So rather than just a mess of firing cells, they can all work in unison to move a leg or fin of the device.

Researchers sometimes mimic animals when creating their biobots (Note: Links have been removed),

Others have taken their cues from nature, creating biologically inspired biohybrids. For example, a group led by researchers at California Institute of Technology developed a biohybrid robot inspired by jellyfish. This device, which they call a medusoid, has arms arranged in a circle. Each arm is micropatterned with protein lines so that cells grow in patterns similar to the muscles in a living jellyfish. When the cells contract, the arms bend inwards, propelling the biohybrid robot forward in nutrient-rich liquid.

More recently, researchers have demonstrated how to steer their biohybrid creations. A group at Harvard used genetically modified heart cells to make a biologically inspired manta ray-shaped robot swim. The heart cells were altered to contract in response to specific frequencies of light – one side of the ray had cells that would respond to one frequency, the other side’s cells responded to another.

Amazing, eh? And, this is quite a recent video; it was published on YouTube on July 7, 2016.

Webster goes on to describe work designed to make these robots hardier and more durable so they can leave the laboratory,

… Here at Case Western Reserve University, we’ve recently begun to investigate … by turning to the hardy marine sea slug Aplysia californica. Since A. californica lives in the intertidal region, it can experience big changes in temperature and environmental salinity over the course of a day. When the tide goes out, the sea slugs can get trapped in tide pools. As the sun beats down, water can evaporate and the temperature will rise. Conversely in the event of rain, the saltiness of the surrounding water can decrease. When the tide eventually comes in, the sea slugs are freed from the tidal pools. Sea slugs have evolved very hardy cells to endure this changeable habitat.

We’ve been able to use Aplysia tissue to actuate a biohybrid robot, suggesting that we can manufacture tougher biobots using these resilient tissues. The devices are large enough to carry a small payload – approximately 1.5 inches long and one inch wide.

Webster has written a fascinating piece and, if you have time, I encourage you to read it in its entirety.

Inspiration from the sea for titanium implants (mussels) and adhesive panels for flexible sensors (octopuses/octopi/octopodes)

I have two sea-inspired news bits both of which concern adhesion.

Mussels and titanium implants

A July 8, 2016 news item on ScienceDaily features some mussel-inspired research from Japan into how to make better titanium implants,

Titanium is used medically in applications such as artificial joints and dental implants. While it is strong and is not harmful to tissues, the metal lacks some of the beneficial biological properties of natural tissues such as bones and natural teeth. Now, based on insights from mussels–which are able to attach themselves very tightly to even metallic surfaces due to special proteins found in their byssal threads–scientists from RIKEN have successfully attached a biologically active molecule to a titanium surface, paving the way for implants that can be more biologically beneficial.

A July 11, 2016 RIKEN press release (also on EurekAlert but dated July 8, 2016), which originated the news item, provides more information,

The work began from earlier discoveries that mussels can attach to smooth surfaces so effectively thanks to a protein, L-DOPA, which is known to be able to bind very strongly to smooth surfaces such as rocks, ceramics, or metals (…). Interestingly, the same protein functions in humans as a precursor to dopamine, and is used as a treatment for Parkinson’s disease.

According to Chen Zhang of the RIKEN Nano Medical Engineering Laboratory, the first author of the paper published in Angewandte Chemie, “We thought it would be interesting to try to use various techniques to attach a biologically active protein—in our case we chose insulin-like growth factor-1, a promoter of cell proliferation—to a titanium surface like those used in implants” (…).

Using a combination of recombinant DNA technology and treatment with tyrosinase, they were able to create a hybrid protein that contained active parts of both the growth factor and L-DOPA. Tests showed that the proteins were able to fold normally, and further experiments in cell cultures demonstrated that the IGF-1 was still functioning normally. Thanks to the incorporation of the L-DOPA, the team was able to confirm that the proteins bound strongly to the titanium surface, and remained attached even when the metal was washed with phosphate-buffered saline, a water-based solution. Zhang says, “This is similar to the powerful properties of mussel adhesive, which can remain fixed to metallic materials even underwater.”

According to Yoshihiro Ito, Team Leader of the Emergent Bioengineering Research Team of the RIKEN Center for Emergent Matter Science, “We are very excited by this finding, because the modification process is a universal one that could be used with other proteins. It could allow us to prepare new cell-growth enhancing materials, with potential applications in cell culture systems and regenerative medicine. And it is particularly interesting that this is an example of biomimetics, where nature can teach us new ways to do things. The mussel has given us insights that could be used to allow us to live healthier lives.”

The work was done by RIKEN researchers in collaboration with Professor Peibiao Zhang of the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, and Professor Yi Wang of the School of Pharmaceutical Sciences, Jilin University. The work was partially supported by the Japan Society for the Promotion of Science KAKENHI (Grant Number 15H01810 and 22220009), CAS-JSPS joint fund (GJHZ1519), and RIKEN MOST joint project.

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

A Bioorthogonal Approach for the Preparation of a Titanium-Binding Insulin-like Growth-Factor-1 Derivative by using Tyrosinase by Chen Zhang, Hideyuki Miyatake, Yu Wang, Takehiko Inaba, Yi Wang, Peibiao Zhang, and Prof. Yoshihiro Ito. Angewandte Chemie International Edition DOI: 10.1002/anie.201603155 Version of Record online: 6 JUL 2016

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

This paper is behind a paywall.

Octopuses/octopi/octopodes and adhesive panels

Before launching into the science part of this news bit, here’s some grammar (from the Octopus Wikipedia entry; Note: Links have been removed),

The standard pluralized form of “octopus” in the English language is “octopuses” /ˈɒktəpʊsɪz/,[10] although the Ancient Greek plural “octopodes” /ɒkˈtɒpədiːz/, has also been used historically.[9] The alternative plural “octopi” — which misguidedly assumes it is a Latin “-us”-word — is considered grammatically incorrect.[11][12][13][14] It is nevertheless used enough to make it notable, and was formally acknowledged by the descriptivist Merriam-Webster 11th Collegiate Dictionary and Webster’s New World College Dictionary. The Oxford English Dictionary (2008 Draft Revision)[15] lists “octopuses”, “octopi”, and “octopodes”, in that order, labelling “octopodes” as rare and noting that “octopi” derives from the apprehension that octōpus comes from Latin.[16] In contrast, New Oxford American Dictionary (3rd Edition 2010) lists “octopuses” as the only acceptable pluralization, with a usage note indicating “octopodes” as being still occasionally used but “octopi” as being incorrect.[17]

Now the news. A July 12, 2016 news item on Nanowerk highlights some research into adhesives and octopuses,

With increased study of bio-adhesives, a significant effort has been made in search for novel adhesives that will combine reversibility, repeated usage, stronger bonds and faster bonding time, non-toxic, and more importantly be effective in wet and other extreme conditions.

A team of Korean scientists-made up of scientists from Korea Institute of Science and Technology (KIST) and UNIST has recently found a way to make building flexible pressure sensors easier–by mimicking the suction cups on octopus’s tentacles.

A July 5, 2016 UNIST (Ulsan National Institute of Science and Technology) press release, which originated the news item, provides more information,

According to the research team, “Although flexible pressure sensors might give future prosthetics and robots a better sense of touch, building them requires a lot of laborious transferring of nano- and microribbons of inorganic semiconductor materials onto polymer sheets.”

In search of an easier way to process this transfer printing, Prof. Hyunhyub Ko (School of Energy and Chemical Engineering, UNIST) and his colleagues turned to the octopus suction cups for inspiration.

An octopus uses its tentacles to move to a new location and uses suction cups underneath each tentacle to grab onto something. Each suction cup contains a cavity whose pressure is controlled by surrounding muscles. These can be made thinner or thicker on demand, increasing or decreasing air pressure inside the cup, allowing for sucking and releasing as desired.

By mimicking muscle actuation to control cavity-pressure-induced adhesion of octopus suckers, Prof. Ko and his team engineered octopus-inspired smart adhesive pads. They used the rubbery material polydimethylsiloxane (PDMS) to create an array of microscale suckers, which included pores that are coated with a thermally responsive polymer to create sucker-like walls.

The team discovered that the best way to replicate organic nature of muscle contractions would be through applied heat. Indeed, at room temperature, the walls of each pit sit in an ‘open’ state, but when the mat is heated to 32°C, the walls contract, creating suction, therby allowing the entire mate to adhere to a material (mimicking the suction function of an octopus). The adhesive strength also spiked from .32 kilopascals to 94 kilopascals at high temperature.

The team reports that the mat worked as envisioned—they made some indium gallium arsenide transistors that sat on a flexible substrate and also used it to move some nanomaterials to a different type of flexible material.

Prof. Ko and his team expect that their smart adhesive pads can be used as the substrate for wearable health sensors, such as Band-Aids or sensors that stick to the skin at normal body temperatures but fall off when rinsed under cold water.

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

Octopus-Inspired Smart Adhesive Pads for Transfer Printing of Semiconducting Nanomembranes by Hochan Lee, Doo-Seung Um, Youngsu Lee, Seongdong Lim, Hyung-jun Kim,  and Hyunhyub Ko. Advanced Materials DOI: 10.1002/adma.201601407 Version of Record online: 20 JUN 2016

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

This paper is behind a paywall.

Photovoltaics as rose petals

Where solar cells (photovoltaics) are concerned, mimimicking plants is a longstanding pursuit. The latest  plant material to be mimicked is the rose petal’s surface. From a June 24, 2016 news item on ScienceDaily,

With a surface resembling that of plants, solar cells improve light-harvesting and thus generate more power. Scientists of KIT (Karlsruhe Institute of Technology) reproduced the epidermal cells of rose petals that have particularly good antireflection properties and integrated the transparent replicas into an organic solar cell. This resulted in a relative efficiency gain of twelve percent. …

Caption: Biomimetics: the epidermis of a rose petal is replicated in a transparent layer which is then integrated into the front of a solar cell. Credit Illustration: Guillaume Gomard, KIT

Caption: Biomimetics: the epidermis of a rose petal is replicated in a transparent layer which is then integrated into the front of a solar cell.
Credit Illustration: Guillaume Gomard, KIT

A June 24, 2016 KIT press release on EurekAlert, which originated the news item, expands on the theme,

Photovoltaics works in a similar way as the photosynthesis of plants. Light energy is absorbed and converted into a different form of energy. In this process, it is important to use a possibly large portion of the sun’s light spectrum and to trap the light from various incidence angles as the angle changes with the sun’s position. Plants have this capability as a result of a long evolution process – reason enough for photovoltaics researchers to look closely at nature when developing solar cells with a broad absorption spectrum and a high incidence angle tolerance.

Scientists at the KIT and the ZSW (Center for Solar Energy and Hydrogen Research Baden-Württemberg) now suggest in their article published in the Advanced Optical Materials journal to replicate the outermost tissue of the petals of higher plants, the so-called epidermis, in a transparent layer and integrate that layer into the front of solar cells in order to increase their efficiency.

First, the researchers at the Light Technology Institute (LTI), the Institute of Microstructure Technology (IMT), the Institute of Applied Physics (APH), and the Zoological Institute (ZOO) of KIT as well as their colleagues from the ZSW investigated the optical properties, and above all, the antireflection effect of the epidermal cells of different plant species. These properties are particularly pronounced in rose petals where they provide stronger color contrasts and thus increase the chance of pollination. As the scientists found out under the electron microscope, the epidermis of rose petals consists of a disorganized arrangement of densely packed microstructures, with additional ribs formed by randomly positioned nanostructures.

In order to exactly replicate the structure of these epidermal cells over a larger area, the scientists transferred it to a mold made of polydimethylsiloxane, a silicon-based polymer, pressed the resulting negative structure into optical glue which was finally left to cure under UV light. “This easy and cost-effective method creates microstructures of a depth and density that are hardly achievable with artificial techniques,” says Dr. Guillaume Gomard, Group Leader “Nanopothonics” at KIT’s LTI.

The scientists then integrated the transparent replica of the rose petal epidermis into an organic solar cell. This resulted in power conversion efficiency gains of twelve percent for vertically incident light. At very shallow incidence angles, the efficiency gain was even higher. The scientists attribute this gain primarily to the excellent omnidirectional antireflection properties of the replicated epidermis that is able to reduce surface reflection to a value below five percent, even for a light incidence angle of nearly 80 degrees. In addition, as examinations using a confocal laser microscope showed, every single replicated epidermal cell works as a microlense. The microlense effect extends the optical path within the solar cell, enhances the light-matter-interaction, and increases the probability that the photons will be absorbed.

“Our method is applicable to both other plant species and other PV technologies,” Guillaume Gomard explains. “Since the surfaces of plants have multifunctional properties, it might be possible in the future to apply multiple of these properties in a single step.” The results of this research lead to another basic question: What is the role of disorganization in complex photonic structures? Further studies are now examining this issue with the perspective that the next generation of solar cells might benefit from their results.

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

Flower Power: Exploiting Plants’ Epidermal Structures for Enhanced Light Harvesting in Thin-Film Solar Cells by Ruben Hünig, Adrian Mertens, Moritz Stephan, Alexander Schulz, Benjamin Richter, Michael Hetterich, Michael Powalla, Uli Lemmer, Alexander Colsmann, and Guillaume Gomard. Advanced Optical Materials  Version of Record online: 30 MAY 2016 DOI: 10.1002/adom.201600046

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

This paper is behind a paywall.

Squeezing out ‘polymer opals’ for smart clothing and more

Researchers at the University of Cambridge have developed a technology for producing ‘polymer opals’ on industrial scales according to a June 3, 2016 news item on Nanowerk (Note: A link has been removed),

Using a new method called Bend-Induced-Oscillatory-Shearing (BIOS), the researchers are now able to produce hundreds of metres of these materials, known as ‘polymer opals’, on a roll-to-roll process. The results are reported in the journal Nature Communications (“Large-scale ordering of nanoparticles using viscoelastic shear processing”).

A June 3, 2016 University of Cambridge press release (also on EurekAlert), which originated the news item, provides more detail (Note: Links have been removed),

Researchers have devised a new method for stacking microscopic marbles into regular layers, producing intriguing materials which scatter light into intense colours, and which change colour when twisted or stretched.

Some of the brightest colours in nature can be found in opal gemstones, butterfly wings and beetles. These materials get their colour not from dyes or pigments, but from the systematically-ordered microstructures they contain.

The team behind the current research, based at Cambridge’s Cavendish Laboratory, have been working on methods of artificially recreating this ‘structural colour’ for several years, but to date, it has been difficult to make these materials using techniques that are cheap enough to allow their widespread use.

In order to make the polymer opals, the team starts by growing vats of transparent plastic nano-spheres. Each tiny sphere is solid in the middle but sticky on the outside. The spheres are then dried out into a congealed mass. By bending sheets containing a sandwich of these spheres around successive rollers the balls are magically forced into perfectly arranged stacks, by which stage they have intense colour.

By changing the sizes of the starting nano-spheres, different colours (or wavelengths) of light are reflected. And since the material has a rubber-like consistency, when it is twisted and stretched, the spacing between the spheres changes, causing the material to change colour. When stretched, the material shifts into the blue range of the spectrum, and when compressed, the colour shifts towards red. When released, the material returns to its original colour. Such chameleon materials could find their way into colour-changing wallpapers, or building coatings that reflect away infrared thermal radiation.

I always like it when there are quotes which seem spontaneous (from the press release),

“Finding a way to coax objects a billionth of a metre across into perfect formation over kilometre scales is a miracle [emphasis mine],” said Professor Jeremy Baumberg, the paper’s senior author. “But spheres are only the first step, as it should be applicable to more complex architectures on tiny scales.”

In order to make polymer opals in large quantities, the team first needed to understand their internal structure so that it could be replicated. Using a variety of techniques, including electron microscopy, x-ray scattering, rheology and optical spectroscopy, the researchers were able to see the three-dimensional position of the spheres within the material, measure how the spheres slide past each other, and how the colours change.

“It’s wonderful [emphasis mine] to finally understand the secrets of these attractive films,” said PhD student Qibin Zhao, the paper’s lead author.

There’s also the commercialization aspect to this work (from the press release),

Cambridge Enterprise, the University’s commercialisation arm which is helping to commercialise the material, has been contacted by more than 100 companies interested in using polymer opals, and a new spin-out Phomera Technologies has been founded. Phomera will look at ways of scaling up production of polymer opals, as well as selling the material to potential buyers. Possible applications the company is considering include coatings for buildings to reflect heat, smart clothing and footwear, or for banknote security [emphasis mine] and packaging applications.

There is a Canadian company already selling its anti-counterfeiting (banknote security) bioinspired technology. It’s called Opalux and it’s not the only bioinspired anti-counterfeiting Canadian technology company, there’s also NanoTech Security which takes its inspiration from a butterfly (Blue Morpho) wing.

Getting back to Cambridge, here’s a link to and a citation for the research team’s paper,

Large-scale ordering of nanoparticles using viscoelastic shear processing by Qibin Zhao, Chris E. Finlayson, David R. E. Snoswell, Andrew Haines, Christian Schäfer, Peter Spahn, Goetz P. Hellmann, Andrei V. Petukhov, Lars Herrmann, Pierre Burdet, Paul A. Midgley, Simon Butler, Malcolm Mackley, Qixin Guo, & Jeremy J. Baumberg. Nature Communications 7, Article number: 11661  doi:10.1038/ncomms11661 Published 03 June 2016

This paper is open access.

There is a video demonstrating the stretchability of their ‘polymer opal’ film

It was posted on YouTube three years ago when the researchers were first successful. It’s nice to see they’ve been successful at getting the technology to the commercialization stage.

Green Hairstreak butterfly could make computer screens more brilliant

When talking about mimicking the nanostructures on butterfly wings, the butterfly in question is the Blue Morpho, usually. In a change of pace, researchers at Australia’s Swinburne University of Technology have focused their attention on the Green Hairstreak butterfly,

Nanostructures on the wings of the Callophrys Rubi or Green Hairstreak butterfly have inspired the design of an artificial material that could be used in photonics and optics technologies. Courtesy: Swinburne University of Technology

Nanostructures on the wings of the Callophrys Rubi or Green Hairstreak butterfly have inspired the design of an artificial material that could be used in photonics and optics technologies. Courtesy: Swinburne University of Technology

A June 1, 2016 Swinburne University of Technology press release describes the work,

Inspired by the intricate structure of a butterfly wing, Swinburne researchers have developed a technique that could be used to make more brilliant computer screens.

The researchers used a special printing technique to create tiny structures similar to those found in the wings of the Callophrys Rubi butterfly, also known as the Green Hairstreak.

In some iridescent butterfly wings, such as the Green Hairstreak, the wing is made up of a pattern of intertwining and curved surfaces, known as a gyroid structure.  This gyroid structure has amazing properties when it comes to its interactions with light.

The researchers used two-beams of light to print at a super-resolution, creating gyroid structures that are three-dimensional and mechanically strong.

Lead author Dr Zongsong Gan from Swinburne’s Centre for Micro-Photonics says that materials made from these artificial gyroids should respond to light at ultrafast speeds making them ideal for high-speed switches.

He says the technique has two significant advantages.

“The first is that it has improved resolution and the second is that the materials fabricated with this technique have better mechanical strength.

“These new gyroid structures could help make more compact light based electronics because, thanks to their smaller size, larger numbers of devices can be integrated onto a single chip.

“However, for three-dimensional devices, smaller and more compact also means there is a higher risk of structure collapse because of weaker mechanical strength.

“Our fabrication technique allows us to make stronger architectures to overcome this problem,” Dr Gan says.

Here’s an image illustrating the work,

Comparison of natural gyroid structure with artificial structure. Courtesy: Swinburne University of Technology

Comparison of natural gyroid structure with artificial structure. Courtesy: Swinburne University of Technology

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

Biomimetic gyroid nanostructures exceeding their natural origins by Zongsong Gan, Mark D. Turner, and Min Gu. Science Advances  13 May 2016: Vol. 2, no. 5, e1600084
DOI: 10.1126/sciadv.1600084

This appears to be an open access paper,

Making better concrete by looking to nature for inspiration

Researchers from the Masssachusetts Institute of Technology (MIT) are working on a new formula for concrete based on bones, shells, and other such natural materials. From a May 25, 2016 news item on Nanowerk (Note: A link has been removed),

Researchers at MIT are seeking to redesign concrete — the most widely used human-made material in the world — by following nature’s blueprints.

In a paper published online in the journal Construction and Building Materials (“Roadmap across the mesoscale for durable and sustainable cement paste – A bioinspired approach”), the team contrasts cement paste — concrete’s binding ingredient — with the structure and properties of natural materials such as bones, shells, and deep-sea sponges. As the researchers observed, these biological materials are exceptionally strong and durable, thanks in part to their precise assembly of structures at multiple length scales, from the molecular to the macro, or visible, level.

A May 26, 2016 MIT news release (also on EurekAlert), which originated the news item, provides more detail,

From their observations, the team, led by Oral Buyukozturk, a professor in MIT’s Department of Civil and Environmental Engineering (CEE), proposed a new bioinspired, “bottom-up” approach for designing cement paste.

“These materials are assembled in a fascinating fashion, with simple constituents arranging in complex geometric configurations that are beautiful to observe,” Buyukozturk says. “We want to see what kinds of micromechanisms exist within them that provide such superior properties, and how we can adopt a similar building-block-based approach for concrete.”

Ultimately, the team hopes to identify materials in nature that may be used as sustainable and longer-lasting alternatives to Portland cement, which requires a huge amount of energy to manufacture.

“If we can replace cement, partially or totally, with some other materials that may be readily and amply available in nature, we can meet our objectives for sustainability,” Buyukozturk says.

“The merger of theory, computation, new synthesis, and characterization methods have enabled a paradigm shift that will likely change the way we produce this ubiquitous material, forever,” Buehler says. “It could lead to more durable roads, bridges, structures, reduce the carbon and energy footprint, and even enable us to sequester carbon dioxide as the material is made. Implementing nanotechnology in concrete is one powerful example [of how] to scale up the power of nanoscience to solve grand engineering challenges.”

From molecules to bridges

Today’s concrete is a random assemblage of crushed rocks and stones, bound together by a cement paste. Concrete’s strength and durability depends partly on its internal structure and configuration of pores. For example, the more porous the material, the more vulnerable it is to cracking. However, there are no techniques available to precisely control concrete’s internal structure and overall properties.

“It’s mostly guesswork,” Buyukozturk says. “We want to change the culture and start controlling the material at the mesoscale.”

As Buyukozturk describes it, the “mesoscale” represents the connection between microscale structures and macroscale properties. For instance, how does cement’s microscopic arrangement affect the overall strength and durability of a tall building or a long bridge? Understanding this connection would help engineers identify features at various length scales that would improve concrete’s overall performance.

“We’re dealing with molecules on the one hand, and building a structure that’s on the order of kilometers in length on the other,” Buyukozturk says. “How do we connect the information we develop at the very small scale, to the information at the large scale? This is the riddle.”

Building from the bottom, up

To start to understand this connection, he and his colleagues looked to biological materials such as bone, deep sea sponges, and nacre (an inner shell layer of mollusks), which have all been studied extensively for their mechanical and microscopic properties. They looked through the scientific literature for information on each biomaterial, and compared their structures and behavior, at the nano-, micro-, and macroscales, with that of cement paste.

They looked for connections between a material’s structure and its mechanical properties. For instance, the researchers found that a deep sea sponge’s onion-like structure of silica layers provides a mechanism for preventing cracks. Nacre has a “brick-and-mortar” arrangement of minerals that generates a strong bond between the mineral layers, making the material extremely tough.

“In this context, there is a wide range of multiscale characterization and computational modeling techniques that are well established for studying the complexities of biological and biomimetic materials, which can be easily translated into the cement community,” says Masic.

Applying the information they learned from investigating biological materials, as well as knowledge they gathered on existing cement paste design tools, the team developed a general, bioinspired framework, or methodology, for engineers to design cement, “from the bottom up.”

The framework is essentially a set of guidelines that engineers can follow, in order to determine how certain additives or ingredients of interest will impact cement’s overall strength and durability. For instance, in a related line of research, Buyukozturk is looking into volcanic ash [emphasis mine] as a cement additive or substitute. To see whether volcanic ash would improve cement paste’s properties, engineers, following the group’s framework, would first use existing experimental techniques, such as nuclear magnetic resonance, scanning electron microscopy, and X-ray diffraction to characterize volcanic ash’s solid and pore configurations over time.

Researchers could then plug these measurements into models that simulate concrete’s long-term evolution, to identify mesoscale relationships between, say, the properties of volcanic ash and the material’s contribution to the strength and durability of an ash-containing concrete bridge. These simulations can then be validated with conventional compression and nanoindentation experiments, to test actual samples of volcanic ash-based concrete.

Ultimately, the researchers hope the framework will help engineers identify ingredients that are structured and evolve in a way, similar to biomaterials, that may improve concrete’s performance and longevity.

“Hopefully this will lead us to some sort of recipe for more sustainable concrete,” Buyukozturk says. “Typically, buildings and bridges are given a certain design life. Can we extend that design life maybe twice or three times? That’s what we aim for. Our framework puts it all on paper, in a very concrete way, for engineers to use.”

This is not the only team looking at new methods for producing the material, my Dec. 24, 2012 posting features a number of ‘concrete’ research projects.

Also, I highlighted the reference to ‘volcanic ash’ as it reminded me of Roman concrete which has lasted for over 2000 years and includes volcanic sand and volcanic rock.  You can read more about it in a Dec. 18, 2014 article by Mark Miller for Ancient Origins where he describes the wonders of the material and what was then a recent discovery of the Romans’ recipe.

I have two links and citations, first, the MIT paper, then the paper on Roman concrete.

Roadmap across the mesoscale for durable and sustainable cement paste – A bioinspired approach by Steven D. Palkovic, Dieter B. Brommer, Kunal Kupwade-Patil, Admir Masic, Markus J. Buehler, Oral Büyüköztürk.Construction and Building Materials Volume 115, 15 July 2016, Pages 13–31.  doi:10.1016/j.conbuildmat.2016.04.020

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar by Marie D. Jackson, Eric N. Landis, Philip F. Brune, Massimo Vitti, Heng Chen, Qinfei Li, Martin Kunz, Hans-Rudolf Wenk, Paulo J. M. Monteiro, and Anthony R. Ingraffea. Proceedings of the National Academy of Sciences  vol. 111 no. 52 18484–18489, doi: 10.1073/pnas.1417456111

The first paper is behind a paywall but the second one appears to be open access.

Mimicking nature’s ‘anti-freeze’

Some frogs can survive being frozen for weeks and that’s the property scientists at the University of Leeds (UK) are trying to mimic according to a May 19, 2016 news item on Nanowerk (Note: A link has been removed),

The new research, published today [May 18, 2016] in the print edition of the Journal of Physical Chemistry B (“Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K”), reveals how glycerol prevents ice crystals from forming in water as the solution is cooled to -35°C, with important implications for improving cryoprotectants used in fertility treatments and food storage.

A May 19, 2016 University of Leeds press release (also on EurekAlert), which originated the news item, provides more detail (Note: A link has been removed),

Dr Lorna Dougan from the University’s School of Physics and Astronomy, who leads the research group, said: “The experiments provide more insight into the fundamental properties of water. It raises questions about what cryoprotectants are doing in living organisms and could help us take steps to understanding how these organisms survive.

“If we understand what glycerol is doing we might be able to fine-tune some of these cryoprotectants that are used to find more effective combinations.”

Cryoprotectant molecules, including glycerol, play an important role in protecting cells and tissues from harmful ice crystals when they are cooled to sub-zero temperatures during freeze storage. Experts have adopted the use of cryoprotectants in fertility treatments and food storage, but not as effectively as in nature.

It is the ability of organisms that can survive in extreme cold environments – known as ‘psychrophiles’ – that inspired the team of physicists to unpick the biological rules that allow their survival.

In winter months, for example, the Eastern Wood frog in North America survives being frozen to temperatures as low as -8°C for weeks, and then in spring thaws out and continues to live perfectly healthily.

To understand how reptiles like the Eastern Wood frog can freeze and thaw, the team used a Science and Technology Facilities Council (STFC) instrument called SANDALS that was purpose-built for investigating the structure of liquids and amorphous materials.

They wanted to answer the fundamental question of how cryoprotectants alter the structure of water at low temperatures, as it is the water structure that is so important in leading to potential ice damage.

The SANDALS instrument allowed the team to see, at the molecular level, that the water and glycerol segregated into clusters. When they looked in more detail, they found the water looked similar to a low density form of itself, showing all the signs it was about to freeze but then it did not. Instead, the glycerol molecules encapsulated the water, preventing the formation of an icy network.

The team will now use these results as a platform for discovering the next generation of cryoprotectants.

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

Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K by J. J. Towey, A. K. Soper, and L. Dougan. J. Phys. Chem. B, 2016, 120 (19), pp 4439–4448 DOI: 10.1021/acs.jpcb.6b01185 Publication Date (Web): March 18, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

I did search for images of Eastern Wood Frogs but they have to be paid for. These frogs must be a very much in demand as I’ve haven’t encountered this before. You can usually find what you want on Wikipedia or on a frog enthusiast site. It’s not an Eastern one but here’s a Wood Frog (from Wikipedia),

Lithobates sylvaticus (Woodfrog) Date: 3 July 2011, 19:31 Author:Brian Gratwicke This file is licensed under the Creative Commons Attribution 2.0 Generic license.

Lithobates sylvaticus (Woodfrog)
Date: 3 July 2011, 19:31
Author: Brian Gratwicke
This file is licensed under the Creative Commons Attribution 2.0 Generic license.