Category Archives: biomimcry

Tough colour and the flower beetle

The flower beetle Torynorrhina flammea. [downloaded from https://www.nanowerk.com/nanotechnology-news2/newsid=58269.php]

That is one gorgeous beetle and a June 17, 2021 news item on Nanowerk reveals that it features in a structural colour story (i.e, how structures rather than pigments create colour),

The unique mechanical and optical properties found in the exoskeleton of a humble Asian beetle has the potential to offer a fascinating new insight into how to develop new, effective bio-inspired technologies.

Pioneering new research by a team of international scientists, including Professor Pete Vukusic from the University of Exeter, has revealed a distinctive, and previously unknown property within the carapace of the flower beetle – a member of the scarab beetle family.

The study showed that the beetle has small micropillars within the carapace – or the upper section of the exoskeleton – that give the insect both strength and flexibility to withstand damage very effectively.

Crucially, these micropillars are incorporated into highly regular layering in the exoskeleton that concurrently give the beetle an intensely bright metallic colour appearance.

A June 18, 2021 University of Exeter press release (also on EurekAlert but published June 17, 2021), delves further into the researchers’ new insights,

For this new study, the scientists used sophisticated modelling techniques to determine which of the two functions – very high mechanical strength or conspicuously bright colour – were more important to the survival of the beetle.

They found that although these micropillars do create a highly enhanced toughness of the beetle shell, they were most beneficial for optimising the scattering of coloured light that generates its conspicuous appearance.

The research is published this week in the leading journal, Proceedings of the National Academy of Sciences, PNAS.

Professor Vukusic, one of three leads of the research along with Professor Li at Virginia Tech and Professor Kolle at MIT [Massachusetts Institute of Technology], said: “The astonishing insights generated by this research have only been possible through close collaborative work between Virginia Tech, MIT, Harvard and Exeter, in labs that trailblaze the fields of materials, mechanics and optics. Our follow-up venture to make use of these bio-inspired principles will be an even more exciting journey.”.

The seeds of the pioneering research were sown more than 16 years ago as part of a short project created by Professor Vukusic in the Exeter undergraduate Physics labs. Those early tests and measurements, made by enthusiastic undergraduate students, revealed the possibility of intriguing multifunctionality.

The original students examined the form and structure of beetles’ carapce to try to understand the simple origin of their colour. They noticed for the first time, however, the presence of strength-inducing micropillars.

Professor Vukusic ultimately carried these initial findings to collaborators Professor Ling Li at Virginia Tech and Professor Mathias Kolle at Harvard and then MIT who specialise in the materials sciences and applied optics. Using much more sophisticated measurement and modelling techniques, the combined research team were also to confirm the unique role played by the micropillars in enhancing the beetles’ strength and toughness without compromising its intense metallic colour.

The results from the study could also help inspire a new generation of bio-inspired materials, as well as the more traditional evolutionary research.

By understanding which of the functions provides the greater benefit to these beetles, scientists can develop new techniques to replicate and reproduce the exoskeleton structure, while ensuring that it has brilliant colour appearance with highly effective strength and toughness.

Professor Vukusic added: “Such natural systems as these never fail to impress with the way in which they perform, be it optical, mechanical or in another area of function. The way in which their optical or mechanical properties appear highly tolerant of all manner of imperfections too, continues to offer lessons to us about scientific and technological avenues we absolutely should explore. There is exciting science ahead of us on this journey.”

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

Microstructural design for mechanical–optical multifunctionality in the exoskeleton of the flower beetle Torynorrhina flammea by Zian Jia, Matheus C. Fernandes, Zhifei Deng, Ting Yang, Qiuting Zhang, Alfie Lethbridge, Jie Yin, Jae-Hwang Lee, Lin Han, James C. Weaver, Katia Bertoldi, Joanna Aizenberg, Mathias Kolle, Pete Vukusic, and Ling Li. PNAS June 22, 2021 118 (25) e2101017118; DOI: https://doi.org/10.1073/pnas.2101017118

This paper is behind a paywall.

The coolest paint

It’s the ‘est’ of it all. The coolest, the whitest, the blackest … Scientists and artists are both pursuing the ‘est’. (More about the pursuit later in this posting.)

In this case, scientists have developed the coolest, whitest paint yet. From an April 16, 2021 news item on Nanowerk,

In an effort to curb global warming, Purdue University engineers have created the whitest paint yet. Coating buildings with this paint may one day cool them off enough to reduce the need for air conditioning, the researchers say.

In October [2020], the team created an ultra-white paint that pushed limits on how white paint can be. Now they’ve outdone that. The newer paint not only is whiter but also can keep surfaces cooler than the formulation that the researchers had previously demonstrated.

“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses,” said Xiulin Ruan, a Purdue professor of mechanical engineering.

Caption: Xiulin Ruan, a Purdue University professor of mechanical engineering, holds up his lab’s sample of the whitest paint on record. Credit: Purdue University/Jared Pike

This is nicely done. Researcher Xiulin Ruan is standing close to a structure that could be said to resemble the sun while in shirtsleeves and sunglasses and holding up a sample of his whitest paint in April (not usually a warm month in Indiana).

An April 15, 2021 Purdue University news release (also on EurkeAlert), which originated the news item, provides more detail about the work and hints about its commercial applications both civilian and military,

The researchers believe that this white may be the closest equivalent of the blackest black, “Vantablack,” [emphasis mine; see comments later in this post] which absorbs up to 99.9% of visible light. The new whitest paint formulation reflects up to 98.1% of sunlight – compared with the 95.5% of sunlight reflected by the researchers’ previous ultra-white paint – and sends infrared heat away from a surface at the same time.

Typical commercial white paint gets warmer rather than cooler. Paints on the market that are designed to reject heat reflect only 80%-90% of sunlight and can’t make surfaces cooler than their surroundings.

The team’s research paper showing how the paint works publishes Thursday (April 15 [2021]) as the cover of the journal ACS Applied Materials & Interfaces.

What makes the whitest paint so white

Two features give the paint its extreme whiteness. One is the paint’s very high concentration of a chemical compound called barium sulfate [emphasis mine] which is also used to make photo paper and cosmetics white.

“We looked at various commercial products, basically anything that’s white,” said Xiangyu Li, a postdoctoral researcher at the Massachusetts Institute of Technology who worked on this project as a Purdue Ph.D. student in Ruan’s lab. “We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they’re really, really white.”

The second feature is that the barium sulfate particles are all different sizes in the paint. How much each particle scatters light depends on its size, so a wider range of particle sizes allows the paint to scatter more of the light spectrum from the sun.

“A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance,” said Joseph Peoples, a Purdue Ph.D. student in mechanical engineering.

There is a little bit of room to make the paint whiter, but not much without compromising the paint.”Although a higher particle concentration is better for making something white, you can’t increase the concentration too much. The higher the concentration, the easier it is for the paint to break or peel off,” Li said.

How the whitest paint is also the coolest

The paint’s whiteness also means that the paint is the coolest on record. Using high-accuracy temperature reading equipment called thermocouples, the researchers demonstrated outdoors that the paint can keep surfaces 19 degrees Fahrenheit cooler than their ambient surroundings at night. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.

The paint’s solar reflectance is so effective, it even worked in the middle of winter. During an outdoor test with an ambient temperature of 43 degrees Fahrenheit, the paint still managed to lower the sample temperature by 18 degrees Fahrenheit.

This white paint is the result of six years of research building on attempts going back to the 1970s to develop radiative cooling paint as a feasible alternative to traditional air conditioners.

Ruan’s lab had considered over 100 different materials, narrowed them down to 10 and tested about 50 different formulations for each material. Their previous whitest paint was a formulation made of calcium carbonate, an earth-abundant compound commonly found in rocks and seashells.

The researchers showed in their study that like commercial paint, their barium sulfate-based paint can potentially handle outdoor conditions. The technique that the researchers used to create the paint also is compatible with the commercial paint fabrication process.

Patent applications for this paint formulation have been filed through the Purdue Research Foundation Office of Technology Commercialization. This research was supported by the Cooling Technologies Research Center at Purdue University and the Air Force Office of Scientific Research [emphasis mine] through the Defense University Research Instrumentation Program (Grant No.427 FA9550-17-1-0368). The research was performed at Purdue’s FLEX Lab and Ray W. Herrick Laboratories and the Birck Nanotechnology Center of Purdue’s Discovery Park.

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

Ultrawhite BaSO4 Paints and Films for Remarkable Daytime Subambient Radiative Cooling by Xiangyu Li, Joseph Peoples, Peiyan Yao, and Xiulin Ruan. ACS Appl. Mater. Interfaces 2021, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acsami.1c02368 Publication Date:April 15, 2021 © 2021 American Chemical Society

This paper is behind a paywall.

Vantablack and the ongoing ‘est’ of blackest

Vantablack’s 99.9% light absorption no longer qualifies it for the ‘blackest black’. A newer standard for the ‘blackest black’ was set by the US National Institute of Standards and Technology at 99.99% light absorption with its N.I.S.T. ultra-black in 2019, although that too seems to have been bested.

I have three postings covering the Vantablack and blackest black story,

The third posting (December 2019) provides a brief summary of the story along with what was the latest from the US National Institute of Standards and Technology. There’s also a little bit about the ‘The Redemption of Vanity’ an art piece demonstrating the blackest black material from the Massachusetts Institute of Technology, which they state has 99.995% (at least) absorption of light.

From a science perspective, the blackest black would be useful for space exploration.

I am surprised there doesn’t seem to have been an artistic rush to work with the whitest white. That impression may be due to the fact that the feuds get more attention than quiet work.

Dark side to the whitest white?

Andrew Parnell, research fellow in physics and astronomy at the University of Sheffield (UK), mentions a downside to obtaining the material needed to produce this cooling white paint in a June 10, 2021 essay on The Conversation (h/t Fast Company), Note: Links have been removed,

… this whiter-than-white paint has a darker side. The energy required to dig up raw barite ore to produce and process the barium sulphite that makes up nearly 60% of the paint means it has a huge carbon footprint. And using the paint widely would mean a dramatic increase in the mining of barium.

Parnell ends his essay with this (Note: Links have been removed),

Barium sulphite-based paint is just one way to improve the reflectivity of buildings. I’ve spent the last few years researching the colour white in the natural world, from white surfaces to white animals. Animal hairs, feathers and butterfly wings provide different examples of how nature regulates temperature within a structure. Mimicking these natural techniques could help to keep our cities cooler with less cost to the environment.

The wings of one intensely white beetle species called Lepidiota stigma appear a strikingly bright white thanks to nanostructures in their scales, which are very good at scattering incoming light. This natural light-scattering property can be used to design even better paints: for example, by using recycled plastic to create white paint containing similar nanostructures with a far lower carbon footprint. When it comes to taking inspiration from nature, the sky’s the limit.

Nano-photosynthesis in your brain as a stroke treatment?

A May 19, 2021 news item on phys.org sheds some light on a new approach to stroke treatments,

Blocked blood vessels in the brains of stroke patients prevent oxygen-rich blood from getting to cells, causing severe damage. Plants and some microbes produce oxygen through photosynthesis. What if there was a way to make photosynthesis happen in the brains of patients? Now, researchers reporting in ACS’ Nano Letters have done just that in cells and in mice, using blue-green algae and special nanoparticles, in a proof-of-concept demonstration.

A May 19, 2021 American Chemical Society (ACS) news release, which originated the news item, provides more information on strokes and how this new approach may prove useful,

Strokes result in the deaths of 5 million people worldwide every year, according to the World Health Organization. Millions more survive, but they often experience disabilities, such as difficulties with speech, swallowing or memory. The most common cause is a blood vessel blockage in the brain, and the best way to prevent permanent brain damage from this type of stroke is to dissolve or surgically remove the blockage as soon as possible. However, those options only work within a narrow time window after the stroke happens and can be risky. Blue-green algae, such as Synechococcus elongatus, have been studied previously to treat the lack of oxygen in heart tissue and tumors using photosynthesis. But the visible light needed to trigger the microbes can’t penetrate the skull, and although near-infrared light can pass through, it is insufficient to directly power photosynthesis. “Up-conversion” nanoparticles, often used for imaging, can absorb near-infrared photons and emit visible light. So, Lin Wang, Zheng Wang, Guobin Wang and colleagues at Huazhong University of Science and Technology wanted to see if they could develop a new approach that could someday be used for stroke patients by combining these parts — S. elongatus, nanoparticles and near-infrared light — in a new “nano-photosynthetic” system.

The researchers paired S. elongatus with neodymium up-conversion nanoparticles that transform tissue-penetrating near-infrared light to a visible wavelength that the microbes can use to photosynthesize. In a cell study, they found that the nano-photosynthesis approach reduced the number of neurons that died after oxygen and glucose deprivation. They then injected the microbes and nanoparticles into mice with blocked cerebral arteries and exposed the mice to near-infrared light. The therapy reduced the number of dying neurons, improved the animals’ motor function and even helped new blood vessels to start growing. Although this treatment is still in the animal testing stage, it has promise to advance someday toward human clinical trials, the researchers say.

The authors acknowledge funding from the National Key Basic Research Program of China, the National Natural Science Foundation of China, the Chinese Ministry of Education’s Science and Technology Program, the Major Scientific and Technological Innovation Projects in Hubei Province, and the Joint Fund of Ministry of Education for Equipment Pre-research.

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

Oxygen-Generating Cyanobacteria Powered by Upconversion-Nanoparticles-Converted Near-Infrared Light for Ischemic Stroke Treatment by Jian Wang, Qiangfei Su, Qiying Lv, Bo Cai, Xiakeerzhati Xiaohalati, Guobin Wang, Zheng Wang, and Lin Wang. Nano Lett. 2021, 21, 11, 4654–4665 DOI: https://doi.org/10.1021/acs.nanolett.1c00719 Publication Date:May 19, 2021 © 2021 American Chemical Society

This paper is behind a paywall.

A lobster’s stretch and strength in a hydrogel

An MIT team has fabricated a hydrogel-based material that mimics the structure of the lobster’s underbelly, the toughest known hydrogel found in nature. Credits: Courtesy of the researchers

I love this lobster. In most photos, they’re food. This shows off the lobster as a living entity while showcasing its underbelly, which is what this story is all about. From an April 23, 2021 news item on phys.org (Note: A link has been removed),

A lobster’s underbelly is lined with a thin, translucent membrane that is both stretchy and surprisingly tough. This marine under-armor, as MIT [Massachusetts Institute of Technology] engineers reported in 2019, is made from the toughest known hydrogel in nature, which also happens to be highly flexible. This combination of strength and stretch helps shield a lobster as it scrabbles across the seafloor, while also allowing it to flex back and forth to swim.

Now a separate MIT team has fabricated a hydrogel-based material that mimics the structure of the lobster’s underbelly. The researchers ran the material through a battery of stretch and impact tests, and showed that, similar to the lobster underbelly, the synthetic material is remarkably “fatigue-resistant,” able to withstand repeated stretches and strains without tearing.

If the fabrication process could be significantly scaled up, materials made from nanofibrous hydrogels could be used to make stretchy and strong replacement tissues such as artificial tendons and ligaments.

The team’s results are published in the journal Matter. The paper’s MIT co-authors include postdocs Jiahua Ni and Shaoting Lin; graduate students Xinyue Liu and Yuchen Sun; professor of aeronautics and astronautics Raul Radovitzky; professor of chemistry Keith Nelson; mechanical engineering professor Xuanhe Zhao; and former research scientist David Veysset Ph.D. ’16, now at Stanford University; along with Zhao Qin, assistant professor at Syracuse University, and Alex Hsieh of the Army Research Laboratory.

An April 23, 2021 MIT news release (also on EurekAlert) by Jennifer Chu, which originated the news item, offers an overview of the groundwork for this latest research along with technical detail about the latest work,

Nature’s twist

In 2019, Lin and other members of Zhao’s group developed a new kind of fatigue-resistant material made from hydrogel — a gelatin-like class of materials made primarily of water and cross-linked polymers. They fabricated the material from ultrathin fibers of hydrogel, which aligned like many strands of gathered straw when the material was repeatedly stretched. This workout also happened to increase the hydrogel’s fatigue resistance.

“At that moment, we had a feeling nanofibers in hydrogels were important, and hoped to manipulate the fibril structures so that we could optimize fatigue resistance,” says Lin.

In their new study, the researchers combined a number of techniques to create stronger hydrogel nanofibers. The process starts with electrospinning, a fiber production technique that uses electric charges to draw ultrathin threads out of polymer solutions. The team used high-voltage charges to spin nanofibers from a polymer solution, to form a flat film of nanofibers, each measuring about 800 nanometers — a fraction of the diameter of a human hair.

They placed the film in a high-humidity chamber to weld the individual fibers into a sturdy, interconnected network, and then set the film in an incubator to crystallize the individual nanofibers at high temperatures, further strengthening the material.

They tested the film’s fatigue-resistance by placing it in a machine that stretched it repeatedly over tens of thousands of cycles. They also made notches in some films and observed how the cracks propagated as the films were stretched repeatedly. From these tests, they calculated that the nanofibrous films were 50 times more fatigue-resistant than the conventional nanofibrous hydrogels.

Around this time, they read with interest a study by Ming Guo, associate professor of mechanical engineering at MIT, who characterized the mechanical properties of a lobster’s underbelly. This protective membrane is made from thin sheets of chitin, a natural, fibrous material that is similar in makeup to the group’s hydrogel nanofibers.

Guo found that a cross-section of the lobster membrane revealed sheets of chitin stacked at 36-degree angles, similar to twisted plywood, or a spiral staircase. This rotating, layered configuration, known as a bouligand structure, enhanced the membrane’s properties of stretch and strength.

“We learned that this bouligand structure in the lobster underbelly has high mechanical performance, which motivated us to see if we could reproduce such structures in synthetic materials,” Lin says.

Angled architecture

Ni, Lin, and members of Zhao’s group teamed up with Nelson’s lab and Radovitzky’s group in MIT’s Institute for Soldier Nanotechnologies, and Qin’s lab at Syracuse University, to see if they could reproduce the lobster’s bouligand membrane structure using their synthetic, fatigue-resistant films.

“We prepared aligned nanofibers by electrospinning to mimic the chinic fibers existed in the lobster underbelly,” Ni says.

After electrospinning nanofibrous films, the researchers stacked each of five films in successive, 36-degree angles to form a single bouligand structure, which they then welded and crystallized to fortify the material. The final product measured 9 square centimeters and about 30 to 40 microns thick — about the size of a small piece of Scotch tape.

Stretch tests showed that the lobster-inspired material performed similarly to its natural counterpart, able to stretch repeatedly while resisting tears and cracks — a fatigue-resistance Lin attributes to the structure’s angled architecture.

“Intuitively, once a crack in the material propagates through one layer, it’s impeded by adjacent layers, where fibers are aligned at different angles,” Lin explains.

The team also subjected the material to microballistic impact tests with an experiment designed by Nelson’s group. They imaged the material as they shot it with microparticles at high velocity, and measured the particles’ speed before and after tearing through the material. The difference in velocity gave them a direct measurement of the material’s impact resistance, or the amount of energy it can absorb, which turned out to be a surprisingly tough 40 kilojoules per kilogram. This number is measured in the hydrated state.

“That means that a 5-millimeter steel ball launched at 200 meters per second would be arrested by 13 millimeters of the material,” Veysset says. “It is not as resistant as Kevlar, which would require 1 millimeter, but the material beats Kevlar in many other categories.”

It’s no surprise that the new material isn’t as tough as commercial antiballistic materials. It is, however, significantly sturdier than most other nanofibrous hydrogels such as gelatin and synthetic polymers like PVA. The material is also much stretchier than Kevlar. This combination of stretch and strength suggests that, if their fabrication can be sped up, and more films stacked in bouligand structures, nanofibrous hydrogels may serve as flexible and tough artificial tissues.

“For a hydrogel material to be a load-bearing artificial tissue, both strength and deformability are required,” Lin says. “Our material design could achieve these two properties.”

If you have the time and the interest, do check out the April 23, 2021 MIT news release, which features a couple of informative GIFs.

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

Strong fatigue-resistant nanofibrous hydrogels inspired by lobster underbelly by Jiahua Ni, Shaoting Lin, Zhao Qin, David Veysset, Xinyue Liu, Yuchen Sun, Alex J. Hsieh, Raul Radovitzky, Keith A. Nelson, Xuanhe Zhao. Matter, 2021; DOI: 10.1016/j.matt.2021.03.023 Published April 23, 2021

This paper is behind a paywall.

A new generation of xenobots made with frog cells

I meant to feature this work last year when it was first announced so I’m delighted a second chance has come around so soon after. From a March 31, 2021 news item on ScienceDaily,

Last year, a team of biologists and computer scientists from Tufts University and the University of Vermont (UVM) created novel, tiny self-healing biological machines from frog cells called “Xenobots” that could move around, push a payload, and even exhibit collective behavior in the presence of a swarm of other Xenobots.

Get ready for Xenobots 2.0.

Here’s a video of the Xenobot 2.0. It’s amazing but, for anyone who has problems with animal experimentation, this may be disturbing,


The next version of Xenobots have been created – they’re faster, live longer, and can now record information. (Source: Doug Blackiston & Emma Lederer)

A March 31, 2021 Tufts University news release by Mike Silver (also on EurekAlert and adapted and published as Scientists Create the Next Generation of Living Robots on the University of Vermont website as a UVM Today story),

The same team has now created life forms that self-assemble a body from single cells, do not require muscle cells to move, and even demonstrate the capability of recordable memory. The new generation Xenobots also move faster, navigate different environments, and have longer lifespans than the first edition, and they still have the ability to work together in groups and heal themselves if damaged. The results of the new research were published today [March 31, 2021] in Science Robotics.

Compared to Xenobots 1.0, in which the millimeter-sized automatons were constructed in a “top down” approach by manual placement of tissue and surgical shaping of frog skin and cardiac cells to produce motion, the next version of Xenobots takes a “bottom up” approach. The biologists at Tufts took stem cells from embryos of the African frog Xenopus laevis (hence the name “Xenobots”) and allowed them to self-assemble and grow into spheroids, where some of the cells after a few days differentiated to produce cilia – tiny hair-like projections that move back and forth or rotate in a specific way. Instead of using manually sculpted cardiac cells whose natural rhythmic contractions allowed the original Xenobots to scuttle around, cilia give the new spheroidal bots “legs” to move them rapidly across a surface. In a frog, or human for that matter, cilia would normally be found on mucous surfaces, like in the lungs, to help push out pathogens and other foreign material. On the Xenobots, they are repurposed to provide rapid locomotion. 

“We are witnessing the remarkable plasticity of cellular collectives, which build a rudimentary new ‘body’ that is quite distinct from their default – in this case, a frog – despite having a completely normal genome,” said Michael Levin, Distinguished Professor of Biology and director of the Allen Discovery Center at Tufts University, and corresponding author of the study. “In a frog embryo, cells cooperate to create a tadpole. Here, removed from that context, we see that cells can re-purpose their genetically encoded hardware, like cilia, for new functions such as locomotion. It is amazing that cells can spontaneously take on new roles and create new body plans and behaviors without long periods of evolutionary selection for those features.”

“In a way, the Xenobots are constructed much like a traditional robot.  Only we use cells and tissues rather than artificial components to build the shape and create predictable behavior.” said senior scientist Doug Blackiston, who co-first authored the study with research technician Emma Lederer. “On the biology end, this approach is helping us understand how cells communicate as they interact with one another during development, and how we might better control those interactions.”

While the Tufts scientists created the physical organisms, scientists at UVM were busy running computer simulations that modeled different shapes of the Xenobots to see if they might exhibit different behaviors, both individually and in groups. Using the Deep Green supercomputer cluster at UVM’s Vermont Advanced Computing Core, the team, led by computer scientists and robotics experts Josh Bongard and Sam Kriegman, simulated the Xenbots under hundreds of thousands of random environmental conditions using an evolutionary algorithm.  These simulations were used to identify Xenobots most able to work together in swarms to gather large piles of debris in a field of particles

“We know the task, but it’s not at all obvious — for people — what a successful design should look like. That’s where the supercomputer comes in and searches over the space of all possible Xenobot swarms to find the swarm that does the job best,” says Bongard. “We want Xenobots to do useful work. Right now we’re giving them simple tasks, but ultimately we’re aiming for a new kind of living tool that could, for example, clean up microplastics in the ocean or contaminants in soil.” 

It turns out, the new Xenobots are much faster and better at tasks such as garbage collection than last year’s model, working together in a swarm to sweep through a petri dish and gather larger piles of iron oxide particles. They can also cover large flat surfaces, or travel through narrow capillary tubes.

These studies also suggest that the in silico [computer] simulations could in the future optimize additional features of biological bots for more complex behaviors. One important feature added in the Xenobot upgrade is the ability to record information.

Now with memory

A central feature of robotics is the ability to record memory and use that information to modify the robot’s actions and behavior. With that in mind, the Tufts scientists engineered the Xenobots with a read/write capability to record one bit of information, using a fluorescent reporter protein called EosFP, which normally glows green. However, when exposed to light at 390nm wavelength, the protein emits red light instead. 

The cells of the frog embryos were injected with messenger RNA coding for the EosFP protein before stem cells were excised to create the Xenobots. The mature Xenobots now have a built-in fluorescent switch which can record exposure to blue light around 390nm.
The researchers tested the memory function by allowing 10 Xenobots to swim around a surface on which one spot is illuminated with a beam of 390nm light. After two hours, they found that three bots emitted red light. The rest remained their original green, effectively recording the “travel experience” of the bots.

This proof of principle of molecular memory could be extended in the future to detect and record not only light but also the presence of radioactive contamination, chemical pollutants, drugs, or a disease condition. Further engineering of the memory function could enable the recording of multiple stimuli (more bits of information) or allow the bots to release compounds or change behavior upon sensation of stimuli. 

“When we bring in more capabilities to the bots, we can use the computer simulations to design them with more complex behaviors and the ability to carry out more elaborate tasks,” said Bongard. “We could potentially design them not only to report conditions in their environment but also to modify and repair conditions in their environment.”

Xenobot, heal thyself

“The biological materials we are using have many features we would like to someday implement in the bots – cells can act like sensors, motors for movement, communication and computation networks, and recording devices to store information,” said Levin. “One thing the Xenobots and future versions of biological bots can do that their metal and plastic counterparts have difficulty doing is constructing their own body plan as the cells grow and mature, and then repairing and restoring themselves if they become damaged. Healing is a natural feature of living organisms, and it is preserved in Xenobot biology.” 

The new Xenobots were remarkably adept at healing and would close the majority of a severe full-length laceration half their thickness within 5 minutes of the injury. All injured bots were able to ultimately heal the wound, restore their shape and continue their work as before. 

Another advantage of a biological robot, Levin adds, is metabolism. Unlike metal and plastic robots, the cells in a biological robot can absorb and break down chemicals and work like tiny factories synthesizing and excreting chemicals and proteins. The whole field of synthetic biology – which has largely focused on reprogramming single celled organisms to produce useful molecules – can now be exploited in these multicellular creatures

Like the original Xenobots, the upgraded bots can survive up to ten days on their embryonic energy stores and run their tasks without additional energy sources, but they can also carry on at full speed for many months if kept in a “soup” of nutrients. 

What the scientists are really after

An engaging description of the biological bots and what we can learn from them is presented in a TED talk by Michael Levin. In his TED Talk, professor Levin describes not only the remarkable potential for tiny biological robots to carry out useful tasks in the environment or potentially in therapeutic applications, but he also points out what may be the most valuable benefit of this research – using the bots to understand how individual cells come together, communicate, and specialize to create a larger organism, as they do in nature to create a frog or human. It’s a new model system that can provide a foundation for regenerative medicine.

Xenobots and their successors may also provide insight into how multicellular organisms arose from ancient single celled organisms, and the origins of information processing, decision making and cognition in biological organisms. 

Recognizing the tremendous future for this technology, Tufts University and the University of Vermont have established the Institute for Computer Designed Organisms (ICDO), to be formally launched in the coming months, which will pull together resources from each university and outside sources to create living robots with increasingly sophisticated capabilities.

The ultimate goal for the Tufts and UVM researchers is not only to explore the full scope of biological robots they can make; it is also to understand the relationship between the ‘hardware’ of the genome and the ‘software’ of cellular communications that go into creating organized tissues, organs and limbs. Then we can gain greater control of that morphogenesis for regenerative medicine, and the treatment of cancer and diseases of aging.

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

A cellular platform for the development of synthetic living machines by Douglas Blackiston, Emma Lederer, Sam Kriegman, Simon Garnier, Joshua Bongard, and Michael Levin. Science Robotics 31 Mar 2021: Vol. 6, Issue 52, eabf1571 DOI: 10.1126/scirobotics.abf1571

This paper is behind a paywall.

An electronics-free, soft robotic dragonfly

From the description on YouTube,

With the ability to sense changes in pH, temperature and oil, this completely soft, electronics-free robot dubbed “DraBot” could be the prototype for future environmental sentinels. …

Music: Joneve by Mello C from the Free Music Archive

A favourite motif in the Art Nouveau movement (more about that later in the post), dragonflies or a facsimile thereof feature in March 25, 2021 Duke University news release (also on EurekAlert) by Ken Kingery,

Engineers at Duke University have developed an electronics-free, entirely soft robot shaped like a dragonfly that can skim across water and react to environmental conditions such as pH, temperature or the presence of oil. The proof-of-principle demonstration could be the precursor to more advanced, autonomous, long-range environmental sentinels for monitoring a wide range of potential telltale signs of problems.

The soft robot is described online March 25 [2021] in the journal Advanced Intelligent Systems.

Soft robots are a growing trend in the industry due to their versatility. Soft parts can handle delicate objects such as biological tissues that metal or ceramic components would damage. Soft bodies can help robots float or squeeze into tight spaces where rigid frames would get stuck.

The expanding field was on the mind of Shyni Varghese, professor of biomedical engineering, mechanical engineering and materials science, and orthopaedic surgery at Duke, when inspiration struck.

“I got an email from Shyni from the airport saying she had an idea for a soft robot that uses a self-healing hydrogel that her group has invented in the past to react and move autonomously,” said Vardhman Kumar, a PhD student in Varghese’s laboratory and first author of the paper. “But that was the extent of the email, and I didn’t hear from her again for days. So the idea sort of sat in limbo for a little while until I had enough free time to pursue it, and Shyni said to go for it.”

In 2012, Varghese and her laboratory created a self-healing hydrogel that reacts to changes in pH in a matter of seconds. Whether it be a crack in the hydrogel or two adjoining pieces “painted” with it, a change in acidity causes the hydrogel to form new bonds, which are completely reversible when the pH returns to its original levels.

Varghese’s hastily written idea was to find a way to use this hydrogel on a soft robot that could travel across water and indicate places where the pH changes. Along with a few other innovations to signal changes in its surroundings, she figured her lab could design such a robot as a sort of autonomous environmental sensor.

With the help of Ung Hyun Ko, a postdoctoral fellow also in Varghese’s laboratory, Kumar began designing a soft robot based on a fly. After several iterations, the pair settled on the shape of a dragonfly engineered with a network of interior microchannels that allow it to be controlled with air pressure.

They created the body–about 2.25 inches long with a 1.4-inch wingspan–by pouring silicon into an aluminum mold and baking it. The team used soft lithography to create interior channels and connected with flexible silicon tubing.

DraBot was born.

“Getting DraBot to respond to air pressure controls over long distances using only self-actuators without any electronics was difficult,” said Ko. “That was definitely the most challenging part.”

DraBot works by controlling the air pressure coming into its wings. Microchannels carry the air into the front wings, where it escapes through a series of holes pointed directly into the back wings. If both back wings are down, the airflow is blocked, and DraBot goes nowhere. But if both wings are up, DraBot goes forward.

To add an element of control, the team also designed balloon actuators under each of the back wings close to DraBot’s body. When inflated, the balloons cause the wings to curl upward. By changing which wings are up or down, the researchers tell DraBot where to go.

“We were happy when we were able to control DraBot, but it’s based on living things,” said Kumar. “And living things don’t just move around on their own, they react to their environment.”

That’s where self-healing hydrogel comes in. By painting one set of wings with the hydrogel, the researchers were able to make DraBot responsive to changes in the surrounding water’s pH. If the water becomes acidic, one side’s front wing fuses with the back wing. Instead of traveling in a straight line as instructed, the imbalance causes the robot to spin in a circle. Once the pH returns to a normal level, the hydrogel “un-heals,” the fused wings separate, and DraBot once again becomes fully responsive to commands.

To beef up its environmental awareness, the researchers also leveraged the sponges under the wings and doped the wings with temperature-responsive materials. When DraBot skims over water with oil floating on the surface, the sponges will soak it up and change color to the corresponding color of oil. And when the water becomes overly warm, DraBot’s wings change from red to yellow.

The researchers believe these types of measurements could play an important part in an environmental robotic sensor in the future. Responsiveness to pH can detect freshwater acidification, which is a serious environmental problem affecting several geologically-sensitive regions. The ability to soak up oils makes such long-distance skimming robots an ideal candidate for early detection of oil spills. Changing colors due to temperatures could help spot signs of red tide and the bleaching of coral reefs, which leads to decline in the population of aquatic life.

The team also sees many ways that they could improve on their proof-of-concept. Wireless cameras or solid-state sensors could enhance the capabilities of DraBot. And creating a form of onboard propellant would help similar bots break free of their tubing.

“Instead of using air pressure to control the wings, I could envision using some sort of synthetic biology that generates energy,” said Varghese. “That’s a totally different field than I work in, so we’ll have to have a conversation with some potential collaborators to see what’s possible. But that’s part of the fun of working on an interdisciplinary project like this.”

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

Microengineered Materials with Self‐Healing Features for Soft Robotics by Vardhman Kumar, Ung Hyun Ko, Yilong Zhou, Jiaul Hoque, Gaurav Arya, Shyni Varghese. Advanced Intelligent Systems DOI: https://doi.org/10.1002/aisy.202100005 First published: 25 March 2021

This paper is open access.

The earlier reference to Art Nouveau gives me an excuse to introduce this March 7, 2020 (?) essay by Bex Simon (artist blacksmith) on her eponymous website.

Dragonflies, in particular, are a very poplar subject matter in the Art Nouveau movement. Art Nouveau, with its wonderful flowing lines and hidden fantasies, is full of symbolism.  The movement was a response to the profound social changes and industrialization of every day life and the style of the moment was, in part, inspired by Japanese art.

Simon features examples of Art Nouveau dragonfly art along with examples of her own take on the subject. She also has this,

[downloaded from https://www.bexsimon.com/dragonflies-and-butterflies-in-art-nouveau/]

This is a closeup of a real dragonfly as seen on Simon’s website. If you have an interest, reading her March 7, 2020 (?) essay and gazing at the images won’t take much time.

Submersible dandelions and the materials they could inspire

Before launching into the news item and if you’re as ignorant about the term as I was, here’s what it means to be a dandelion clock, from the dandelion clock definition on Wiktionary [Note: Links have been removed]),

A single stem of a dandelion in its post-flowering state with the downy covering of its head intact. The term is applied when the flower is used, or is thought of as suitable for use, in a children’s pastime by which the number of puffs needed to blow the filamentous achenes from a dandelion is supposed to tell the time.

A March 3, 2021 news item on phys.org announces dandelion research (Note: A link has been removed),

Fields are covered with dandelions in spring, a very common plant with yellow-gold flowers and toothed leaves. When they wither, the flowers turn into fluffy white seed heads that, like tiny parachutes, are scattered around by the wind. Taraxacum officinale—its scientific name—inspired legends and poems and has been used for centuries as a natural remedy for many ailments.

Now, thanks to a study conducted at the University of Trento [Università di Trento], dandelions will inspire new engineered materials. The air trapping capacity of dandelion clocks [emphasis mine] submerged in water has been measured in the lab for the first time. The discovery paves the way for the development of new and advanced devices and technologies that could be used in a broad range of applications, for example, to create devices or materials that retain air bubbles under water.

I found the dandelion squeezing sequence to be quite fascinating.

A March 3, 2021 Università di Trento press release (also on EurekAlert), which originated the news item, provides more detail,

The study was coordinated by Nicola Pugno, professor of the University of Trento and coordinator of the Laboratory of Bio-inspired, Bionic, Nano, Meta Materials & Mechanics at the Department of Civil, Environmental and Mechanical Engineering.
The discovery was given international prominence by “Materials Today Bio”, a multidisciplinary journal focused on the interface between biology and materials science, chemistry, physics, engineering, and medicine.

Nicola Pugno outlined how the research unfolded: “Diego Misseroni and I started to work on a discovery that my daughter made, in her first year in high school. She noticed that dandelion clocks, when submerged by water, turn silvery because they trap air. We have quantified this discovery. For the first time, we have measured the air trapping capacity of dandelion clocks in a laboratory setting. This paper demonstrated that kids and young adults can make significant discoveries by observing nature”.

When submerged in water, the research team observed, the soft seed heads turn silver in color, become thinner and take on a rhombus-like shape. The team then developed an analytical model to measure the mechanical properties of the flower, in order to mimic them and create re-engineered dandelion-like materials.

Bioinspired engineering can explore different opportunities thanks to this discovery, such as miniaturized parachute-like elements to develop innovative devices and advanced, light and low-cost technological solutions to trap and transport air bubbles underwater. These materials could be used, for example, in underwater operations.

It’s been a while (see my Nov. 21, 2018 posting ‘Regenerating tooth enamel’) since I’ve featured research from Nicola Pugno here.

Here’s a link to and a citation for Pugno’s dandelion-ispired work

Air-encapsulating elastic mechanism of submerged Taraxacum blowballs by M.C.Pugno, D.Misseroni, N.M.Pugno. Materials Today Bio Volume 9, January 2021, 100095 DOI: 10.1016/j.mtbio.2021.100095

This paper is open access.

A 3D spider web, a VR (virtual reality) setup, and sonification (music)

Markus Buehler and his musical spider webs are making news again.

Caption: Cross-sectional images (shown in different colors) of a spider web were combined into this 3D image and translated into music. Credit: Isabelle Su and Markus Buehler

The image (so pretty) you see in the above comes from a Markus Buehler presentation that was made at the American Chemical Society (ACS) meeting. ACS Spring 2021 being held online April 5-30, 2021. The image was also shown during a press conference which the ACS has made available for public viewing. More about that later in this posting.

The ACS issued an April 12, 2021 news release (also on EurekAlert), which provides details about Buehler’s latest work on spider webs and music,

Spiders are master builders, expertly weaving strands of silk into intricate 3D webs that serve as the spider’s home and hunting ground. If humans could enter the spider’s world, they could learn about web construction, arachnid behavior and more. Today, scientists report that they have translated the structure of a web into music, which could have applications ranging from better 3D printers to cross-species communication and otherworldly musical compositions.

The researchers will present their results today at the spring meeting of the American Chemical Society (ACS). ACS Spring 2021 is being held online April 5-30 [2021]. Live sessions will be hosted April 5-16, and on-demand and networking content will continue through April 30 [2021]. The meeting features nearly 9,000 presentations on a wide range of science topics.

“The spider lives in an environment of vibrating strings,” says Markus Buehler, Ph.D., the project’s principal investigator, who is presenting the work. “They don’t see very well, so they sense their world through vibrations, which have different frequencies.” Such vibrations occur, for example, when the spider stretches a silk strand during construction, or when the wind or a trapped fly moves the web.

Buehler, who has long been interested in music, wondered if he could extract rhythms and melodies of non-human origin from natural materials, such as spider webs. “Webs could be a new source for musical inspiration that is very different from the usual human experience,” he says. In addition, by experiencing a web through hearing as well as vision, Buehler and colleagues at the Massachusetts Institute of Technology (MIT), together with collaborator Tomás Saraceno at Studio Tomás Saraceno, hoped to gain new insights into the 3D architecture and construction of webs.

With these goals in mind, the researchers scanned a natural spider web with a laser to capture 2D cross-sections and then used computer algorithms to reconstruct the web’s 3D network. The team assigned different frequencies of sound to strands of the web, creating “notes” that they combined in patterns based on the web’s 3D structure to generate melodies. The researchers then created a harp-like instrument and played the spider web music in several live performances around the world.

The team also made a virtual reality setup that allowed people to visually and audibly “enter” the web. “The virtual reality environment is really intriguing because your ears are going to pick up structural features that you might see but not immediately recognize,” Buehler says. “By hearing it and seeing it at the same time, you can really start to understand the environment the spider lives in.”

To gain insights into how spiders build webs, the researchers scanned a web during the construction process, transforming each stage into music with different sounds. “The sounds our harp-like instrument makes change during the process, reflecting the way the spider builds the web,” Buehler says. “So, we can explore the temporal sequence of how the web is being constructed in audible form.” This step-by-step knowledge of how a spider builds a web could help in devising “spider-mimicking” 3D printers that build complex microelectronics. “The spider’s way of ‘printing’ the web is remarkable because no support material is used, as is often needed in current 3D printing methods,” he says.

In other experiments, the researchers explored how the sound of a web changes as it’s exposed to different mechanical forces, such as stretching. “In the virtual reality environment, we can begin to pull the web apart, and when we do that, the tension of the strings and the sound they produce change. At some point, the strands break, and they make a snapping sound,” Buehler says.

The team is also interested in learning how to communicate with spiders in their own language. They recorded web vibrations produced when spiders performed different activities, such as building a web, communicating with other spiders or sending courtship signals. Although the frequencies sounded similar to the human ear, a machine learning algorithm correctly classified the sounds into the different activities. “Now we’re trying to generate synthetic signals to basically speak the language of the spider,” Buehler says. “If we expose them to certain patterns of rhythms or vibrations, can we affect what they do, and can we begin to communicate with them? Those are really exciting ideas.”

You can go here for the April 12, 2021 ‘Making music from spider webs’ ACS press conference’ it runs about 30 mins. and you will hear some ‘spider music’ played.

Getting back to the image and spider webs in general, we are most familiar with orb webs (in the part of Canada where I from if nowhere else), which look like spirals and are 2D. There are several other types of webs some of which are 3D, like tangle webs, also known as cobwebs, funnel webs and more. See this March 18, 2020 article “9 Types of Spider Webs: Identification + Pictures & Spiders” by Zach David on Beyond the Treat for more about spiders and their webs. If you have the time, I recommend reading it.

I’ve been following Buehler’s spider web/music work for close to ten years now; the latest previous posting is an October 23, 2019 posting where you’ll find a link to an application that makes music from proteins (spider webs are made up of proteins; scroll down about 30% of the way; it’s in the 2nd to last line of the quoted text about the embedded video).

Here is a video (2 mins. 17 secs.) of a spider web music performance that Buehler placed on YouTube,

Feb 3, 2021

Markus J. Buehler

Spider’s Canvas/Arachonodrone show excerpt at Palais de Tokyo, Paris, on November 2018. Video by MIT CAST. More videos can be found on www.arachnodrone.com. The performance was commissioned by Studio Tomás Saraceno (STS), in the context of Saraceno’s carte blanche exhibition, ON AIR. Spider’s Canvas/Arachnodrone was performed by Isabelle Su and Ian Hattwick on the spider web instrument, Evan Ziporyn on the EWI (Electronic Wind Instrument), and Christine Southworth on the guitar and EBow (Electronic Bow)

You can find more about the spider web music and Buehler’s collaborators on http://www.arachnodrone.com/,

Spider’s Canvas / Arachnodrone is inspired by the multifaceted work of artist Tomas Saraceno, specifically his work using multiple species of spiders to make sculptural webs. Different species make very different types of webs, ranging not just in size but in design and functionality. Tomas’ own web sculptures are in essence collaborations with the spiders themselves, placing them sequentially over time in the same space, so that the complex, 3-dimensional sculptural web that results is in fact built by several spiders, working together.

Meanwhile, back among the humans at MIT, Isabelle Su, a Course 1 doctoral student in civil engineering, has been focusing on analyzing the structure of single-species spider webs, specifically the ‘tent webs’ of the cyrtophora citricola, a tropical spider of particular interest to her, Tomas, and Professor Markus Buehler. Tomas gave the department a cyrtophora spider, the department gave the spider a space (a small terrarium without glass), and she in turn built a beautiful and complex web. Isabelle then scanned it in 3D and made a virtual model. At the suggestion of Evan Ziporyn and Eran Egozy, she then ported the model into Unity, a VR/game making program, where a ‘player’ can move through it in numerous ways. Evan & Christine Southworth then worked with her on ‘sonifying’ the web and turning it into an interactive virtual instrument, effectively turning the web into a 1700-string resonating instrument, based on the proportional length of each individual piece of silk and their proximity to one another. As we move through the web (currently just with a computer trackpad, but eventually in a VR environment), we create a ‘sonic biome’: complex ‘just intonation’ chords that come in and out of earshot according to which of her strings we are closest to. That part was all done in MAX/MSP, a very flexible high level audio programming environment, which was connected with the virtual environment in Unity. Our new colleague Ian Hattwick joined the team focusing on sound design and spatialization, building an interface that allowed him the sonically ‘sculpt’ the sculpture in real time, changing amplitude, resonance, and other factors. During this performance at Palais de Tokyo, Isabelle toured the web – that’s what the viewer sees – while Ian adjusted sounds, so in essence they were together “playing the web.” Isabelle provides a space (the virtual web) and a specific location within it (by driving through), which is what the viewer sees, from multiple angles, on the 3 scrims. The location has certain acoustic potentialities, and Ian occupies them sonically, just as a real human performer does in a real acoustic space. A rough analogy might be something like wandering through a gothic cathedral or a resonant cave, using your voice or an instrument at different volumes and on different pitches to find sonorous resonances, echoes, etc. Meanwhile, Evan and Christine are improvising with the web instrument, building on Ian’s sound, with Evan on EWI (Electronic Wind Instrument) and Christine on electric guitar with EBow.

For the visuals, Southworth wanted to create the illusion that the performers were actually inside the web. We built a structure covered in sharkstooth scrim, with 3 projectors projecting in and through from 3 sides. Southworth created images using her photographs of local Lexington, MA spider webs mixed with slides of the scan of the web at MIT, and then mixed those images with the projection of the game, creating an interactive replica of Saraceno’s multi-species webs.

If you listen to the press conference, you will hear Buehler talk about practical applications for this work in materials science.

Lobster-inspired 3D printed concrete

A January 19, 2021 news item on ScienceDaily highlights bioinspired 3D printing of concrete,

New research shows that patterns inspired by lobster shells can make 3D printed concrete stronger, to support more complex and creative architectural structures.

Digital manufacturing technologies like 3D concrete printing (3DCP) have immense potential to save time, effort and material in construction.

They also promise to push the boundaries of architectural innovation, yet technical challenges remain in making 3D printed concrete strong enough for use in more free-form structures.

In a new experimental study, researchers at RMIT University [Australia] looked to the natural strength of lobster shells to design special 3D printing patterns.

Their bio-mimicking spiral patterns improved the overall durability of the 3D printed concrete, as well as enabling the strength to be precisely directed for structural support where needed.

Video: Carelle Mulawa-Richards

A January 19, 2021 RMIT University press release (also on EurekAlert) by Gosia Kaszubska, which originated the news item, goes into technical detail about the research once you get past the ‘fluffy’ bits,

When the team combined the twisting patterns with a specialised concrete mix enhanced with steel fibres, the resulting material was stronger than traditionally-made concrete.

Lead researcher Dr Jonathan Tran said 3D printing and additive manufacturing opened up opportunities in construction for boosting both efficiency and creativity.

“3D concrete printing technology has real potential to revolutionise the construction industry, and our aim is to bring that transformation closer,” said Tran, a senior lecturer in structured materials and design at RMIT.

“Our study explores how different printing patterns affect the structural integrity of 3D printed concrete, and for the first time reveals the benefits of a bio-inspired approach in 3DCP.

“We know that natural materials like lobster exoskeletons?have evolved into high-performance structures over millions of years, so by mimicking their key advantages we can follow where nature has already innovated.”

3D printing for construction

The automation of concrete construction is set to transform how we build, with construction the next frontier in the automation and data-driven revolution known as industry 4.0.

A 3D concrete printer builds houses or makes structural components by depositing the material layer-by-layer, unlike the traditional approach of casting concrete in a mould.

With the latest technology, a house can be 3D printed in just 24 hours for about half the cost, while construction on the world’s first 3D printed community began in 2019 in Mexico.

The emerging industry is already supporting architectural and engineering innovation, such as a 3D printed office building in Dubai, a nature-mimicking concrete bridge in Madrid and The Netherlands’ sail-shaped “Europe Building”.

The research team in RMIT’s School of Engineering focuses on 3D printing concrete, exploring ways to enhance the finished product through different combinations of printing pattern design, material choices, modelling, design optimisation and reinforcement options.

Patterns for printing

The most conventional pattern used in 3D printing is unidirectional, where layers are laid down on top of each other in parallel lines.

The new study published in a special issue of 3D Printing and Additive Manufacturing investigated the effect of different printing patterns on the strength of steel fibre-enhanced concrete.

Previous research by the RMIT team found that including 1-2% steel fibres in the concrete mix reduces defects and porosity, increasing strength. The fibres also help the concrete harden early without deformation, enabling higher structures to be built.

The team tested the impact of printing the concrete in helicoidal patterns (inspired by the internal structure of lobster shells), cross-ply and quasi-isotropic patterns (similar to those used for laminated composite structures and layer-by-layer deposited composites) and standard unidirectional patterns.

Supporting complex structures

The results showed strength improvement from each of the patterns, compared with unidirectional printing, but Tran said the spiral patterns hold the most promise for supporting complex 3D printed concrete structures.

“As lobster shells are naturally strong and naturally curved, we know this could help us deliver stronger concrete shapes like arches and flowing or twisted structures,” he said.

“This work is in early stages so we need further research to test how the concrete performs on a wider range of parameters, but our initial experimental results show we are on the right track.”

Further studies will be supported through a new large-scale mobile concrete 3D printer recently acquired by RMIT – making it the first research institution in the southern hemisphere to commission a machine of this kind.

The 5×5m robotic printer will be used by the team to research the 3D printing of houses, buildings and large structural components.

The team will also use the machine to explore the potential for 3D printing with concrete made with recycled waste materials such as soft plastic aggregate.

The work is connected to a new project with industry partners Replas and SR Engineering, focusing on sound-dampening walls made from post-consumer recycled soft plastics and concrete, which was recently supported with an Australian Government Innovations Connections grant.

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

Influences of Printing Pattern on Mechanical Performance of Three-Dimensional-Printed Fiber-Reinforced Concrete by Luong Pham, Guoxing Lu, and Phuong Tran. 3D Printing and Additive Manufacturing DOI: https://doi.org/10.1089/3dp.2020.0172 Published Online:30 Dec 2020

This paper is open access.

A lotus root-inspired hydrogel fiber for surgical sutures

By FotoosRobin – originally posted to Flickr as Lotus root, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=4826529

The lotus (Nelumbo nucifera) rhizome (mass of roots) is not the prettiest part of the lotus but its fibers (and presumably fiber from other parts of the lotus plant) served as inspiration for a hydrogel that might be used as a surgical suture according to a Jan. 14, 2021 news item on phys.org (Note: Links have been removed),

“The lotus roots may break, but the fiber remains joined”—an old Chinese saying that reflects the unique structure and mechanical properties of the lotus fiber. The outstanding mechanical properties of lotus fibers can be attributed to their unique spiral structure, which provides an attractive model for biomimetic design of artificial fibers.

In a new study published in Nano Letters, a team led by Prof. Yu Shuhong from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) reported a bio-inspired lotus-fiber-mimetic spiral structure bacterial cellulose (BC) hydrogel fiber with high strength, high toughness, excellent biocompatibility, good stretchability, and high energy dissipation.

A Jan. 14, 2021 University of Science and Technology of China press release on the Chinese Academy of Sciences website (also on EurekAlert), which originated the news item, describes the new hydrogel in more detail,

Unlike polymer-based hydrogel, the newly designed biomimetic hydrogel fiber (BHF) is based on the BC hydrogel with 3D cellulose nanofiber networks produced by bacteria. The cellulose nanofibers provide the reversible hydrogen bonding network that results in unique mechanical properties.

The researchers applied a constant tangential force to the pretreated BC hydrogel along the cross-sectional direction. Then, the two sides of the hydrogel were subjected to opposite tangential forces, and local plastic deformation occurred.

The hydrogen bonds in the 3D network of cellulose nanofibers were broken by the tangential force, causing the hydrogel strip to twist spirally and the network to slip and deform. When the tangential force was removed, the hydrogen bonds reformed between the nanofibers, and the spiral structure of the fiber was fixed.

Benefited from lotus-fiber-mimetic spiral structure, the toughness of BHF can reach ?116.3 MJ m-3, which is more than nine times higher than those of non-spiralized BC hydrogel fiber. Besides, once the BHF is stretched, it is nearly non-resilient.

Combining outstanding mechanical properties with excellent biocompatibility derived from BC, BHF is a promising hydrogel fiber for biomedical material, especially for surgical suture, a commonly used structural biomedical material for wound repair.

Compared with commercial surgical suture with higher modulus, the BHF has similar modulus and strength to soft tissue, like skin. The outstanding stretchability and energy dissipation of BHF allow it to absorb energy from the tissue deformation around a wound and effectively protect the wound from rupture, which makes BHF an ideal surgical suture.

What’s more, the porous structure of BHF also allows it to adsorb functional small molecules, such as antibiotics or anti-inflammatory compounds, and sustainably release them on wounds. With an appropriate design, BHF would be a powerful platform for many medical applications.

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

Bio-Inspired Lotus-Fiber-like Spiral Hydrogel Bacterial Cellulose Fibers by Qing-Fang Guan, Zi-Meng Han, YinBo Zhu, Wen-Long Xu, Huai-Bin Yang, Zhang-Chi Ling, Bei-Bei Yan, Kun-Peng Yang, Chong-Han Yin, HengAn Wu, and Shu-Hong Yu. Nano Lett. 2021, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acs.nanolett.0c03707 Publication Date:January 5, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.