Tag Archives: biomimetics

Bioinspired, biomimetic stimulation for the next generation of neuroprosthetics

ETH researchers have developed a prosthetic leg that communicates with the brain via natural signals. (Photograph: Keystone) Courtesy: ETH Zurich

A February 21, 2024 ETH Zurich press release by Ori Schipper (also on EurekAlert) announces a ‘nature-inspired’ or bioinspired approach to neuroprosthetics,

Prostheses that connect to the nervous system have been available for several years. Now, researchers at ETH Zurich have found evidence that neuroprosthetics work better when they use signals that are inspired by nature.

In brief

*Neuroprostheses are electro-​mechanical devices that are connected to the nervous system. As yet, these are unable to provide natural communication with the brain. Instead, they often evoke artificial, unpleasant sensations, similar to a feeling of tingles over the skin.
*This paraesthesia might be caused by overstimulation of the nervous system. ETH Zurich researchers together with colleagues in Germany, Serbia and Russia have proposed that neuroprosthetics should transmit biomimetic signals that are easier for the brain to understand.
*These new findings are relevant to arm and leg prostheses as well as various other aids and devices, including spinal implants and electrodes for brain stimulation. 

A few years ago, a team of researchers working under Professor Stanisa Raspopovic at the ETH Zurich Neuroengineering Lab gained worldwide attention when they announced that their prosthetic legs had enabled amputees to feel sensations from this artificial body part for the first time. Unlike commercial leg prostheses, which simply provide amputees with stability and support, the ETH researchers’ prosthetic device was connected to the sciatic nerve in the test subjects’ thigh via implanted electrodes.

This electrical connection enabled the neuroprosthesis to communicate with the patient’s brain, for example relaying information on the constant changes in pressure detected on the sole of the prosthetic foot when walking. This gave the test subjects greater confidence in their prosthesis – and it enabled them to walk considerably faster on challenging terrains. “Our experimental leg prosthesis succeeded in evoking natural sensations. That’s something current neuroprostheses are mainly unable to do; instead, they mostly evoke artificial, unpleasant sensations,” Raspopovic says.

This is probably because today’s neuroprosthetics are using time-​constant electrical pulses to stimulate the nervous system. “That’s not only unnatural, but also inefficient,” Raspopovic says. In a recently published paper, he and his team used the example of their leg prostheses to highlight the benefits of using naturally inspired, biomimetic stimulation to develop the next generation of neuroprosthetics.

Model simulates activation of nerves in the sole

To generate these biomimetic signals, Natalija Katic – a doctoral student in Raspopovic’s research group – developed a computer model called FootSim. It is based on data collected by collaborators in Canada, who recorded the activity of natural receptors, named mechanoreceptors, in the sole of the foot while touching different points on the feet of volunteers with a vibrating rod.

The model simulates the dynamic behaviour of large numbers of mechanoreceptors in the sole of the foot and generates the neural signals that shoot up the nerves in the leg towards the brain – from the moment the heel strikes the ground and the weight of the body starts to shift forward to the outside of the foot until the toes push off the ground ready for the next step. “Thanks to this model, we can see how semsory receptors from the sole, and the connected nerves, behave during walking or running, which is experimentally impossible to measure” Katic says.

Information overload in the spinal cord

To assess how closely the biomimetic signals calculated by the model correspond to the signals emitted by real neurons, Giacomo Valle – a postdoc in Raspopovic’s research group – worked with colleagues in Germany, Serbia and Russia on experiments with cats, whose nervous system processes movement in a similar way to that of humans. The experiments took place in 2019 at the Pavlov Institute of Physiology in St. Petersburg and were carried out in accordance with the relevant European Union guidelines.

The researchers implanted electrodes, connecting some to the nerve in the leg and some to the spinal cord to discover how the signals are transmitted through the nervous system. When the researchers applied pressure to the bottom of the cat’s paw, thereby evoking the natural neural response that occurs when a cat takes a step, the peculiar pattern of activity recorded in the spinal cord did indeed resemble the patterns that were elicited in the spinal cord when the researchers stimulated the leg nerve with biomimetic signals.

By contrast, the conventional approach of time-​constant stimulation of the sciatic nerve in the cat’s thigh elicited a markedly different pattern of activation in the spinal cord. “This clearly shows that the commonly used stimulation methods cause the neural networks in the spine to be flooded with information,” Valle says. “This information overload could be the reason for the unpleasant sensations or paraesthesia reported by some users of neuroprosthetics,” Raspopovic adds.

Learning the language of the nervous system

In their clinical trial with leg amputees, the researchers were able to show that biomimetic stimulation is superior to time-​constant stimulation. Their work clearly demonstrated how the signals that mimicked nature produced better results: not only were the test subjects able to climb steps faster, they also made fewer mistakes in a task that required them to climb the same steps while spelling words backwards. “Biomimetic neurostimulation allows subjects to concentrate on other things while walking,” Raspopovic says, “so we concluded that this type of stimulation is more naturally processed and less taxing on the brain.”

Raspopovic, whose lab forms part of the ETH Institute of Robotics and Intelligent Systems, believes that these new findings are not only relevant to the limb prostheses he and his team have been working on for over half a decade. He argues that the need to move away from unnatural, time-​constant stimulation towards biomimetic signals also applies to a whole series of other aids and devices, including spinal implants and electrodes for brain stimulation. “We need to learn the language of the nervous system,” Raspopovic says. “Then we’ll be able to communicate with the brain in ways it really understands.”

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

Biomimetic computer-to-brain communication enhancing naturalistic touch sensations via peripheral nerve stimulation by Giacomo Valle, Natalija Katic Secerovic, Dominic Eggemann, Oleg Gorskii, Natalia Pavlova, Francesco M. Petrini, Paul Cvancara, Thomas Stieglitz, Pavel Musienko, Marko Bumbasirevic & Stanisa Raspopovic. Nature Communications volume 15, Article number: 1151 (2024) DOI: https://doi.org/10.1038/s41467-024-45190-6 Published: 20 February 2024

This paper is open access.

It was a bit of a surprise to see mention of some Canadian collaborators with regard to the earlier work featuring FootSim, a computer model Here’s a link to and a citation to that paper, this version is housed at ETH Zurich,

Modeling foot sole cutaneous afferents: FootSim by Natalija Katic, Rodrigo Kazu Siqueira, Luke Cleland, Nicholas Strzalkowski, Leah Bent, Stanisa Raspopovic, and Hannes Saal. Originally published in: iScience 26(1), DOI https://doi.org/10.1016/j.isci.2022.105874 Publication date: 2023-01-20 Permanent link: https://doi.org/10.3929/ethz-b-000591102

This paper too is open access.

Fairy-like robot powered by wind and light

Caption: For their artificial fairy, Hao Zeng and Jianfeng Yang got inspired by dandelion seeds. Credit: Jianfeng Yang / Tampere University

That image makes me think of Tinker Bell (the fairy in the novel/play/movie with ‘Peter Pan’ in its titles) but I can also see how the researchers were inspired by dandelion seeds, which we used to call ‘wishes’.

Dandelion Seeds Free Stock Photo – Public Domain Pictures

A January 30, 2023 news item on ScienceDaily announces the fairy-like robot,

The development of stimuli-responsive polymers has brought about a wealth of material-related opportunities for next-generation small-scale, wirelessly controlled soft-bodied robots. For some time now, engineers have known how to use these materials to make small robots that can walk, swim and jump. So far, no one has been able to make them fly.

Researchers of the Light Robots group at Tampere University [Finland] are now researching how to make smart material fly. Hao Zeng, Academy Research Fellow and the group leader, and Jianfeng Yang, a doctoral researcher, have come up with a new design for their project called FAIRY — Flying Aero-robots based on Light Responsive Materials Assembly. They have developed a polymer-assembly robot that flies by wind and is controlled by light.

A January 26, 2023 Tampere University press release (also on EurekAlert but published January 30, 2023), which originated the news item, elucidates why the researchers are excited about their work,

Superior to its natural counterparts, this artificial seed is equipped with a soft actuator. The actuator is made of light-responsive liquid crystalline elastomer, which induces opening or closing actions of the bristles upon visible light excitation,” explains Hao Zeng.

The artificial fairy is controlled by light

The artificial fairy developed by Zeng and Yang has several biomimetic features. Because of its high porosity (0.95) and lightweight (1.2 mg) structure, it can easily float in the air directed by the wind. What is more, a stable separated vortex ring generation enables long-distance wind-assisted travelling.

“The fairy can be powered and controlled by a light source, such as a laser beam or LED,” Zeng says.

This means that light can be used to change the shape of the tiny dandelion seed-like structure. The fairy can adapt manually to wind direction and force by changing its shape. A light beam can also be used to control the take-off and landing actions of the polymer assembly.

Potential application opportunities in agriculture

Next, the researchers will focus on improving the material sensitivity to enable the operation of the device in sunlight. In addition, they will up-scale the structure so that it can carry micro-electronic devices such as GPS and sensors as well as biochemical compounds.

According to Zeng, there is potential for even more significant applications.

“It sounds like science fiction, but the proof-of-concept experiments included in our research show that the robot we have developed provides an important step towards realistic applications suitable for artificial pollination,” he reveals.

In the future, millions of artificial dandelion seeds carrying pollen could be dispersed freely by natural winds and then steered by light toward specific areas with trees awaiting pollination.

“This would have a huge impact on agriculture globally since the loss of pollinators due to global warming has become a serious threat to biodiversity and food production,” Zeng says.

Challenges remain to be solved

However, many problems need to be solved first. For example, how to control the landing spot in a precise way, and how to reuse the devices and make them biodegradable? These issues require close collaboration with materials scientists and people working on microrobotics.

The FAIRY project started in September 2021 and will last until August 2026. It is funded by the Academy of Finland. The flying robot is researched in cooperation with Dr. Wenqi Hu from Max Planck Institute for Intelligent Systems (Germany) and Dr. Hang Zhang from Aalto University.

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

Dandelion-Inspired, Wind-Dispersed Polymer-Assembly Controlled by Light by Jianfeng Yang, Hang Zhang, Alex Berdin, Wenqi Hu, Hao Zeng. Advanced Science Volume 10, Issue 7 March 3, 2023 2206752 DOI: https://doi.org/10.1002/advs.202206752 First published online: 27 December 2022

This paper is open access.

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.

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.

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.

World’s first liquid retina prosthesis

The new artificial liquid retina is biomimetic and consists of an aqueous component in which photoactive polymeric nanoparticles (whose size is of 350 nanometres, thus about 1/100 of the diameter of a hair) are suspended, going to replace the damaged photoreceptors. Credit: IIT-Istituto Italiano di Tecnologia [image downloaded from https://www.medgadget.com/2020/06/injectable-liquid-prosthesis-to-treat-retinal-diseases-developed.html]

A June 29, 2020 news item on Nanowerk announces the world’s first liquid retina prosthesis,

Researchers at IIT-Istituto Italiano di Tecnologia (Italian Institute of Technology) has led to the revolutionary development of an artificial liquid retinal prosthesis to counteract the effects of diseases such as retinitis pigmentosa and age-related macular degeneration that cause the progressive degeneration of photoreceptors of the retina, resulting in blindness.

The multidisciplinary team is composed by researchers from the IIT’s Center for Synaptic Neuroscience and Technology in Genoa coordinated by Fabio Benfenati and a team from the IIT’s Center for Nano Science and Technology in Milan coordinated by Guglielmo Lanzani, and it also involves the IRCCS Ospedale Sacrocuore Don Calabria in Negrar (Verona) with the team lead by Grazia Pertile, the IRCCS Ospedale Policlinico San Martino in Genoa and the CNR in Bologna. The research has been supported by Fondazione 13 Marzo Onlus, Fondazione Ra.Mo., Rare Partners srl and Fondazione Cariplo.

The study represents the state of the art in retinal prosthetics and is an evolution of the planar artificial retinal model developed by the same team in 2017 and based on organic semiconductor materials (Nature Materials 2017, 16: 681-689).

A June 30, 2020 IIT-Istituto Italiano di Tecnologia (Italian Institute of Technology) press release (also on EurekAlert but published June 29, 2020) provides more detail,

The “second generation” artificial retina is biomimetic, offers high spatial resolution and consists of an aqueous component in which photoactive polymeric nanoparticles (whose size is of 350 nanometres, thus about 1/100 of the diameter of a hair) are suspended, going to replace the damaged photoreceptors.

The experimental results show that the natural light stimulation of nanoparticles, in fact, causes the activation of retinal neurons spared from degeneration, thus mimicking the functioning of photoreceptors in healthy subjects.

Compared to other existing approaches, the new liquid nature of the prosthesis ensures fast and less traumatic surgery that consist of microinjections of nanoparticles directly under the retina, where they remain trapped and replace the degenerated photoreceptors; this method also ensures an increased effectiveness.

The data collected show also that the innovative experimental technique represents a valid alternative to the methods used to date to restore the photoreceptive capacity of retinal neurons while preserving their spatial resolution, laying a solid foundation for future clinical trials in humans. Moreover, the development of these photosensitive nanomaterials opens the way to new future applications in neuroscience and medicine.

“Our experimental results highlight the potential relevance of nanomaterials in the development of second-generation retinal prostheses to treat degenerative retinal blindness, and represents a major step forward” Fabio Benfenati commented. “The creation of a liquid artificial retinal implant has great potential to ensure a wide-field vision and high-resolution vision. Enclosing the photoactive polymers in particles that are smaller than the photoreceptors, increases the active surface of interaction with the retinal neurons, allows to easily cover the entire retinal surface and to scale the photoactivation at the level of a single photoreceptor.”

“In this research we have applied nanotechnology to medicine” concludes Guglielmo Lanzani. “In particular in our labs we have realized polymer nanoparticles that behave like tiny photovoltaic cells, based on carbon and hydrogen, fundamental components of the biochemistry of life. Once injected into the retina, these nanoparticles form small aggregates the size of which is comparable to that of neurons, that effectively behave like photoreceptors.”

“The surgical procedure for the subretinal injection of photoactive nanoparticles is minimally invasive and potentially replicable over time, unlike planar retinal prostheses” adds Grazia Pertile, Director at Operating Unit of Ophthalmology at IRCCS Ospedale Sacro Cuore Don Calabria. “At the same time maintaining the advantages of polymeric prosthesis, which is naturally sensitive to the light entering the eye and does not require glasses, cameras or external energy sources.”

The research study is based on preclinical models and further experimentations will be fundamental to make the technique a clinical treatment for diseases such as retinitis pigmentosa and age-related macular degeneration.

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

Subretinally injected semiconducting polymer nanoparticles rescue vision in a rat model of retinal dystrophy by José Fernando Maya-Vetencourt, Giovanni Manfredi, Maurizio Mete, Elisabetta Colombo, Mattia Bramini, Stefano Di Marco, Dmytro Shmal, Giulia Mantero, Michele Dipalo, Anna Rocchi, Mattia L. DiFrancesco, Ermanno D. Papaleo, Angela Russo, Jonathan Barsotti, Cyril Eleftheriou, Francesca Di Maria, Vanessa Cossu, Fabio Piazza, Laura Emionite, Flavia Ticconi, Cecilia Marini, Gianmario Sambuceti, Grazia Pertile, Guglielmo Lanzani & Fabio Benfenati. Nature Nanotechnology (2020) DOI: https://doi.org/10.1038/s41565-020-0696-3 Published: 29 June 2020

This paper is behind a paywall.

AI (artificial intelligence) and a hummingbird robot

Every once in a while I stumble across a hummingbird robot story (my August 12, 2011 posting and my August 1, 2014 posting). Here’s what the hummingbird robot looks like now (hint: there’s a significant reduction in size),

Caption: Purdue University researchers are building robotic hummingbirds that learn from computer simulations how to fly like a real hummingbird does. The robot is encased in a decorative shell. Credit: Purdue University photo/Jared Pike

I think this is the first time I’ve seen one of these projects not being funded by the military, which explains why the researchers are more interested in using these hummingbird robots for observing wildlife and for rescue efforts in emergency situations. Still, they do acknowledge theses robots could also be used in covert operations.

From a May 9, 2019 news item on ScienceDaily,

What can fly like a bird and hover like an insect?

Your friendly neighborhood hummingbirds. If drones had this combo, they would be able to maneuver better through collapsed buildings and other cluttered spaces to find trapped victims.

Purdue University researchers have engineered flying robots that behave like hummingbirds, trained by machine learning algorithms based on various techniques the bird uses naturally every day.

This means that after learning from a simulation, the robot “knows” how to move around on its own like a hummingbird would, such as discerning when to perform an escape maneuver.

Artificial intelligence, combined with flexible flapping wings, also allows the robot to teach itself new tricks. Even though the robot can’t see yet, for example, it senses by touching surfaces. Each touch alters an electrical current, which the researchers realized they could track.

“The robot can essentially create a map without seeing its surroundings. This could be helpful in a situation when the robot might be searching for victims in a dark place — and it means one less sensor to add when we do give the robot the ability to see,” said Xinyan Deng, an associate professor of mechanical engineering at Purdue.

The researchers even have a video,

A May 9, 2019 Purdue University news release (also on EurekAlert), which originated the news item, provides more detail,


The researchers [presented] their work on May 20 at the 2019 IEEE International Conference on Robotics and Automation in Montreal. A YouTube video is available at https://www.youtube.com/watch?v=hl892dHqfA&feature=youtu.be. [it’s the video I’ve embedded in the above]

Drones can’t be made infinitely smaller, due to the way conventional aerodynamics work. They wouldn’t be able to generate enough lift to support their weight.

But hummingbirds don’t use conventional aerodynamics – and their wings are resilient. “The physics is simply different; the aerodynamics is inherently unsteady, with high angles of attack and high lift. This makes it possible for smaller, flying animals to exist, and also possible for us to scale down flapping wing robots,” Deng said.

Researchers have been trying for years to decode hummingbird flight so that robots can fly where larger aircraft can’t. In 2011, the company AeroVironment, commissioned by DARPA, an agency within the U.S. Department of Defense, built a robotic hummingbird that was heavier than a real one but not as fast, with helicopter-like flight controls and limited maneuverability. It required a human to be behind a remote control at all times.

Deng’s group and her collaborators studied hummingbirds themselves for multiple summers in Montana. They documented key hummingbird maneuvers, such as making a rapid 180-degree turn, and translated them to computer algorithms that the robot could learn from when hooked up to a simulation.

Further study on the physics of insects and hummingbirds allowed Purdue researchers to build robots smaller than hummingbirds – and even as small as insects – without compromising the way they fly. The smaller the size, the greater the wing flapping frequency, and the more efficiently they fly, Deng says.

The robots have 3D-printed bodies, wings made of carbon fiber and laser-cut membranes. The researchers have built one hummingbird robot weighing 12 grams – the weight of the average adult Magnificent Hummingbird – and another insect-sized robot weighing 1 gram. The hummingbird robot can lift more than its own weight, up to 27 grams.

Designing their robots with higher lift gives the researchers more wiggle room to eventually add a battery and sensing technology, such as a camera or GPS. Currently, the robot needs to be tethered to an energy source while it flies – but that won’t be for much longer, the researchers say.

The robots could fly silently just as a real hummingbird does, making them more ideal for covert operations. And they stay steady through turbulence, which the researchers demonstrated by testing the dynamically scaled wings in an oil tank.

The robot requires only two motors and can control each wing independently of the other, which is how flying animals perform highly agile maneuvers in nature.

“An actual hummingbird has multiple groups of muscles to do power and steering strokes, but a robot should be as light as possible, so that you have maximum performance on minimal weight,” Deng said.

Robotic hummingbirds wouldn’t only help with search-and-rescue missions, but also allow biologists to more reliably study hummingbirds in their natural environment through the senses of a realistic robot.

“We learned from biology to build the robot, and now biological discoveries can happen with extra help from robots,” Deng said.
Simulations of the technology are available open-source at https://github.com/
purdue-biorobotics/flappy
.

Early stages of the work, including the Montana hummingbird experiments in collaboration with Bret Tobalske’s group at the University of Montana, were financially supported by the National Science Foundation.

The researchers have three paper on arxiv.org for open access peer review,

Learning Extreme Hummingbird Maneuvers on Flapping Wing Robots
Fan Fei, Zhan Tu, Jian Zhang, and Xinyan Deng
Purdue University, West Lafayette, IN, USA
https://arxiv.org/abs/1902.0962

Biological studies show that hummingbirds can perform extreme aerobatic maneuvers during fast escape. Given a sudden looming visual stimulus at hover, a hummingbird initiates a fast backward translation coupled with a 180-degree yaw turn, which is followed by instant posture stabilization in just under 10 wingbeats. Consider the wingbeat frequency of 40Hz, this aggressive maneuver is carried out in just 0.2 seconds. Inspired by the hummingbirds’ near-maximal performance during such extreme maneuvers, we developed a flight control strategy and experimentally demonstrated that such maneuverability can be achieved by an at-scale 12- gram hummingbird robot equipped with just two actuators. The proposed hybrid control policy combines model-based nonlinear control with model-free reinforcement learning. We use model-based nonlinear control for nominal flight control, as the dynamic model is relatively accurate for these conditions. However, during extreme maneuver, the modeling error becomes unmanageable. A model-free reinforcement learning policy trained in simulation was optimized to ‘destabilize’ the system and maximize the performance during maneuvering. The hybrid policy manifests a maneuver that is close to that observed in hummingbirds. Direct simulation-to-real transfer is achieved, demonstrating the hummingbird-like fast evasive maneuvers on the at-scale hummingbird robot.

Acting is Seeing: Navigating Tight Space Using Flapping Wings
Zhan Tu, Fan Fei, Jian Zhang, and Xinyan Deng
Purdue University, West Lafayette, IN, USA
https://arxiv.org/abs/1902.0868

Wings of flying animals can not only generate lift and control torques but also can sense their surroundings. Such dual functions of sensing and actuation coupled in one element are particularly useful for small sized bio-inspired robotic flyers, whose weight, size, and power are under stringent constraint. In this work, we present the first flapping-wing robot using its flapping wings for environmental perception and navigation in tight space, without the need for any visual feedback. As the test platform, we introduce the Purdue Hummingbird, a flapping-wing robot with 17cm wingspan and 12 grams weight, with a pair of 30-40Hz flapping wings driven by only two actuators. By interpreting the wing loading feedback and its variations, the vehicle can detect the presence of environmental changes such as grounds, walls, stairs, obstacles and wind gust. The instantaneous wing loading can be obtained through the measurements and interpretation of the current feedback by the motors that actuate the wings. The effectiveness of the proposed approach is experimentally demonstrated on several challenging flight tasks without vision: terrain following, wall following and going through a narrow corridor. To ensure flight stability, a robust controller was designed for handling unforeseen disturbances during the flight. Sensing and navigating one’s environment through actuator loading is a promising method for mobile robots, and it can serve as an alternative or complementary method to visual perception.

Flappy Hummingbird: An Open Source Dynamic Simulation of Flapping Wing Robots and Animals
Fan Fei, Zhan Tu, Yilun Yang, Jian Zhang, and Xinyan Deng
Purdue University, West Lafayette, IN, USA
https://arxiv.org/abs/1902.0962

Insects and hummingbirds exhibit extraordinary flight capabilities and can simultaneously master seemingly conflicting goals: stable hovering and aggressive maneuvering, unmatched by small scale man-made vehicles. Flapping Wing Micro Air Vehicles (FWMAVs) hold great promise for closing this performance gap. However, design and control of such systems remain challenging due to various constraints. Here, we present an open source high fidelity dynamic simulation for FWMAVs to serve as a testbed for the design, optimization and flight control of FWMAVs. For simulation validation, we recreated the hummingbird-scale robot developed in our lab in the simulation. System identification was performed to obtain the model parameters. The force generation, open- loop and closed-loop dynamic response between simulated and experimental flights were compared and validated. The unsteady aerodynamics and the highly nonlinear flight dynamics present challenging control problems for conventional and learning control algorithms such as Reinforcement Learning. The interface of the simulation is fully compatible with OpenAI Gym environment. As a benchmark study, we present a linear controller for hovering stabilization and a Deep Reinforcement Learning control policy for goal-directed maneuvering. Finally, we demonstrate direct simulation-to-real transfer of both control policies onto the physical robot, further demonstrating the fidelity of the simulation.

Enjoy!

Colo(u)r-changing building surfaces thanks to gold nanoparticles

Gold, at the nanoscale, has different properties than it has at the macroscale and research at the University of Cambridge has found a new way to exploit gold’s unique properties at the nanoscale according to a May 13, 2019 news item item on ScienceDaily,

The smallest pixels yet created — a million times smaller than those in smartphones, made by trapping particles of light under tiny rocks of gold — could be used for new types of large-scale flexible displays, big enough to cover entire buildings.

The colour pixels, developed by a team of scientists led by the University of Cambridge, are compatible with roll-to-roll fabrication on flexible plastic films, dramatically reducing their production cost. The results are reported in the journal Science Advances [May 10, 2019].

A May 10,2019 University of Cambridge press release (also on EurekAlert), which originated the news item, delves further into the research,

It has been a long-held dream to mimic the colour-changing skin of octopus or squid, allowing people or objects to disappear into the natural background, but making large-area flexible display screens is still prohibitively expensive because they are constructed from highly precise multiple layers.

At the centre of the pixels developed by the Cambridge scientists is a tiny particle of gold a few billionths of a metre across. The grain sits on top of a reflective surface, trapping light in the gap in between. Surrounding each grain is a thin sticky coating which changes chemically when electrically switched, causing the pixel to change colour across the spectrum.

The team of scientists, from different disciplines including physics, chemistry and manufacturing, made the pixels by coating vats of golden grains with an active polymer called polyaniline and then spraying them onto flexible mirror-coated plastic, to dramatically drive down production cost.

The pixels are the smallest yet created, a million times smaller than typical smartphone pixels. They can be seen in bright sunlight and because they do not need constant power to keep their set colour, have an energy performance that makes large areas feasible and sustainable. “We started by washing them over aluminized food packets, but then found aerosol spraying is faster,” said co-lead author Hyeon-Ho Jeong from Cambridge’s Cavendish Laboratory.

“These are not the normal tools of nanotechnology, but this sort of radical approach is needed to make sustainable technologies feasible,” said Professor Jeremy J Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research. “The strange physics of light on the nanoscale allows it to be switched, even if less than a tenth of the film is coated with our active pixels. That’s because the apparent size of each pixel for light is many times larger than their physical area when using these resonant gold architectures.”

The pixels could enable a host of new application possibilities such as building-sized display screens, architecture which can switch off solar heat load, active camouflage clothing and coatings, as well as tiny indicators for coming internet-of-things devices.
The team are currently working at improving the colour range and are looking for partners to develop the technology further.

The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC) and the China Scholarship Council.

This image accompanies the press release,

Caption: eNPoMs formed from gold nanoparticles (Au NPs) encapsulated in a conductive polymer shell. Credit: NanoPhotonics Cambridge/Hyeon-Ho Jeong, Jialong Peng Credit: NanoPhotonics Cambridge/Hyeon-Ho Jeong, Jialong Peng

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

Scalable electrochromic nanopixels using plasmonics by Jialong Peng, Hyeon-Ho Jeong, Qianqi Lin, Sean Cormier, Hsin-Ling Liang, Michael F. L. De Volder, Silvia Vignolini, and Jeremy J. Baumberg. Science Advances Vol. 5, no. 5, eaaw2205 DOI: 10.1126/sciadv.aaw2205 Published: 01 May 2019

This paper appears to be open access.

Iridescent giant clams could point the way to safety, climatologically speaking

Giant clams in Palau (Cynthia Barnett)

These don’t look like any clams I’ve ever seen but that is the point of Cynthia Barnett’s absorbing Sept. 10, 2018 article for The Atlantic (Note: A link has been removed),

Snorkeling amid the tree-tangled rock islands of Ngermid Bay in the western Pacific nation of Palau, Alison Sweeney lingers at a plunging coral ledge, photographing every giant clam she sees along a 50-meter transect. In Palau, as in few other places in the world, this means she is going to be underwater for a skin-wrinkling long time.

At least the clams are making it easy for Sweeney, a biophysicist at the University of Pennsylvania. The animals plump from their shells like painted lips, shimmering in blues, purples, greens, golds, and even electric browns. The largest are a foot across and radiate from the sea floor, but most are the smallest of the giant clams, five-inch Tridacna crocea, living higher up on the reef. Their fleshy Technicolor smiles beam in all directions from the corals and rocks of Ngermid Bay.

… Some of the corals are bleached from the conditions in Ngermid Bay, where naturally high temperatures and acidity mirror the expected effects of climate change on the global oceans. (Ngermid Bay is more commonly known as “Nikko Bay,” but traditional leaders and government officials are working to revive the indigenous name of Ngermid.)

Even those clams living on bleached corals are pulsing color, like wildflowers in a white-hot desert. Sweeney’s ponytail flows out behind her as she nears them with her camera. They startle back into their fluted shells. Like bashful fairytale creatures cursed with irresistible beauty, they cannot help but draw attention with their sparkly glow.

Barnett makes them seem magical and perhaps they are (Note: A link has been removed),

It’s the glow that drew Sweeney’s attention to giant clams, and to Palau, a tiny republic of more than 300 islands between the Philippines and Guam. Its sun-laden waters are home to seven of the world’s dozen giant-clam species, from the storied Tridacna gigas—which can weigh an estimated 550 pounds and measure over four feet across—to the elegantly fluted Tridacna squamosa. Sweeney first came to the archipelago in 2009, while working on animal iridescence as a post-doctoral fellow at the University of California at Santa Barbara. Whether shimmering from a blue morpho butterfly’s wings or a squid’s skin, iridescence is almost always associated with a visual signal—one used to attract mates or confuse predators. Giant clams’ luminosity is not such a signal. So, what is it?

In the years since, Sweeney and her colleagues have discovered that the clams’ iridescence is essentially the outer glow of a solar transformer—optimized over millions of years to run on sunlight and algal biofuel. Giant clams reach their cartoonish proportions thanks to an exceptional ability to grow their own photosynthetic algae in vertical farms spread throughout their flesh. Sweeney and other scientists think this evolved expertise may shed light on alternative fuel technologies and other industrial solutions for a warming world.

Barnett goes on to describe Palau’s relationship to the clams and the clams’ environment,

Palau’s islands have been inhabited for at least 3,400 years, and from the start, giant clams were a staple of diet, daily life, and even deity. Many of the islands’ oldest-surviving tools are crafted of thick giant-clam shell: arched-blade adzes, fishhooks, gougers, heavy taro-root pounders. Giant-clam shell makes up more than three-fourths of some of the oldest shell middens in Palau, a percentage that decreases through the centuries. Archaeologists suggest that the earliest islanders depleted the giant clams that crowded the crystalline shallows, then may have self-corrected. Ancient Palauan conservation law, known as bul, prohibited fishing during critical spawning periods, or when a species showed signs of over-harvesting.

Before the Christianity that now dominates Palauan religion sailed in on eighteenth-century mission ships, the culture’s creation lore began with a giant clam called to life in an empty sea. The clam grew bigger and bigger until it sired Latmikaik, the mother of human children, who birthed them with the help of storms and ocean currents.

The legend evokes giant clams in their larval phase, moving with the currents for their first two weeks of life. Before they can settle, the swimming larvae must find and ingest one or two photosynthetic alga, which later multiply, becoming self-replicating fuel cells. After the larvae down the alga and develop a wee shell and a foot, they kick around like undersea farmers, looking for a sunny spot for their crop. When they’ve chosen a well-lit home in a shallow lagoon or reef, they affix to the rock, their shell gaping to the sky. After the sun hits and photosynthesis begins, the microalgae will multiply to millions, or in the case of T. gigas, billions, and clam and algae will live in symbiosis for life.

Giant clam is a beloved staple in Palau and many other Pacific islands, prepared raw with lemon, simmered into coconut soup, baked into a savory pancake, or sliced and sautéed in a dozen other ways. But luxury demand for their ivory-like shells and their adductor muscle, which is coveted as high-end sashimi and an alleged aphrodisiac, has driven T. gigas extinct in China, Taiwan, and other parts of their native habitat. Some of the toughest marine-protection laws in the world, along with giant-clam aquaculture pioneered here, have helped Palau’s wild clams survive. The Palau Mariculture Demonstration Center raises hundreds of thousands of giant clams a year, supplying local clam farmers who sell to restaurants and the aquarium trade and keeping pressure off the wild population. But as other nations have wiped out their clams, Palau’s 230,000-square-mile ocean territory is an increasing target of illegal foreign fishers.

Barnett delves into how the country of Palau is responding to the voracious appetite for the giant clams and other marine life,

Palau, drawing on its ancient conservation tradition of bul, is fighting back. In 2015, President Tommy Remengesau Jr. signed into law the Palau National Marine Sanctuary Act, which prohibits fishing in 80 percent of Palau’s Exclusive Economic Zone and creates a domestic fishing area in the remaining 20 percent, set aside for local fishers selling to local markets. In 2016, the nation received a $6.6 million grant from Japan to launch a major renovation of the Palau Mariculture Demonstration Center. Now under construction at the waterfront on the southern tip of Malakal Island, the new facility will amp up clam-aquaculture research and increase giant-clam production five-fold, to more than a million seedlings a year.

Last year, Palau amended its immigration policy to require that all visitors sign a pledge to behave in an ecologically responsible manner. The pledge, stamped into passports by an immigration officer who watches you sign, is written to the island’s children:

Children of Palau, I take this pledge, as your guest, to preserve and protect your beautiful and unique island home. I vow to tread lightly, act kindly and explore mindfully. I shall not take what is not given. I shall not harm what does not harm me. The only footprints I shall leave are those that will wash away.

The pledge is winning hearts and public-relations awards. But Palau’s existential challenge is still the collective “we,” the world’s rising carbon emissions and the resulting upturns in global temperatures, sea levels, and destructive storms.

F. Umiich Sengebau, Palau’s Minister for Natural Resources, Environment, and Tourism, grew up on Koror and is full of giant-clam proverbs, wisdom and legends from his youth. He tells me a story I also heard from an elder in the state of Airai: that in old times, giant clams were known as “stormy-weather food,” the fresh staple that was easy to collect and have on hand when it was too stormy to go out fishing.

As Palau faces the storms of climate change, Sengebau sees giant clams becoming another sort of stormy-weather food, serving as a secure source of protein; a fishing livelihood; a glowing icon for tourists; and now, an inspiration for alternative energy and other low-carbon technologies. “In the old days, clams saved us,” Sengebau tells me. “I think there’s a lot of power in that, a great power and meaning in the history of clams as food, and now clams as science.”

I highly recommend Barnett’s article, which is one article in a larger series, from a November 6, 2017 The Atlantic press release,

The Atlantic is expanding the global footprint of its science writing today with a multi-year series to investigate life in all of its multitudes. The series, “Life Up Close,” created with support from Howard Hughes Medical Institute’s Department of Science Education (HHMI), begins today at TheAtlantic.com. In the first piece for the project, “The Zombie Diseases of Climate Change,” The Atlantic’s Robinson Meyer travels to Greenland to report on the potentially dangerous microbes emerging from thawing Arctic permafrost.

The project is ambitious in both scope and geographic reach, and will explore how life is adapting to our changing planet. Journalists will travel the globe to examine these changes as they happen to microbes, plants, and animals in oceans, grasslands, forests, deserts, and the icy poles. The Atlantic will question where humans should look for life next: from the Martian subsurface, to Europa’s oceans, to the atmosphere of nearby stars and beyond. “Life Up Close” will feature at least twenty reported pieces continuing through 2018.

“The Atlantic has been around for 160 years, but that’s a mere pinpoint in history when it comes to questions of life and where it started, and where we’re going,” said Ross Andersen, The Atlantic’s senior editor who oversees science, tech, and health. “The questions that this project will set out to tackle are critical; and this support will allow us to cover new territory in new and more ambitious ways.”

About The Atlantic:
Founded in 1857 and today one of the fastest growing media platforms in the industry, The Atlantic has throughout its history championed the power of big ideas and continues to shape global debate across print, digital, events, and video platforms. With its award-winning digital presence TheAtlantic.com and CityLab.com on cities around the world, The Atlantic is a multimedia forum on the most critical issues of our times—from politics, business, urban affairs, and the economy, to technology, arts, and culture. The Atlantic is celebrating its 160th anniversary this year. Bob Cohn is president of The Atlantic and Jeffrey Goldberg is editor in chief.

About the Howard Hughes Medical Institute (HHMI) Department of Science Education:
HHMI is the leading private nonprofit supporter of scientific research and science education in the United States. The Department of Science Education’s BioInteractive division produces free, high quality educational media for science educators and millions of students around the globe, its HHMI Tangled Bank Studios unit crafts powerful stories of scientific discovery for television and big screens, and its grants program aims to transform science education in universities and colleges. For more information, visit www.hhmi.org.

Getting back to the giant clams, sometimes all you can do is marvel, eh?

Moths with sound absorption stealth technology

The cabbage tree emperor moth (Thomas Neil) [downloaded from https://www.cbc.ca/radio/quirks/nov-17-2018-greenland-asteroid-impact-short-people-in-the-rain-forest-reef-islands-and-sea-level-and-more-1.4906857/how-moths-evolved-a-kind-of-stealth-jet-technology-to-sneak-past-bats-1.4906866]

I don’t think I’ve ever seen a more gorgeous moth and it seems a perfect way to enter 2019, from a November 16, 2018 news item on CBC (Canadian Broadcasting Corporation),

A species of silk moth has evolved special sound absorbing scales on its wings to absorb the sonar pulses from hunting bats. This is analogous to the special coatings on stealth aircraft that allow them to be nearly invisible to radar.

“It’s a battle out there every night, insects flying for their lives trying to avoid becoming a bat’s next dinner,” said Dr. Marc Holderied, the senior author on the paper and an associate professor in the School of Biological Sciences at the University of Bristol.

“If you manage to absorb some of these sound energies, it would make you look smaller and let you be detectable over a shorter distance because echoe isn’t strong enough outside the detection bubble.”

Many moths have ears that warn them when a bat is nearby. But not the big and juicy cabbage tree emperor moths which would ordinarily make the perfect meal for bats.

The researchers prepared a brief animated feature illustrating the research,

Prior to publication of the study, the scientists made a presentation at the Acoustical Society of America’s 176th Meeting, held in conjunction with the Canadian Acoustical Association’s 2018 Acoustics Week, Nov. 5-9 at the Victoria Conference Centre in Victoria, Canada according to a November 7, 2018 University of Bristol press release (also on EurekAlert but submitted by the Acoustical Society of America on November 6, 2018),

Moths are a mainstay food source for bats, which use echolocation (biological sonar) to hunt their prey. Scientists such as Thomas Neil, from the University of Bristol in the U.K., are studying how moths have evolved passive defenses over millions of years to resist their primary predators.

While some moths have evolved ears that detect the ultrasonic calls of bats, many types of moths remain deaf. In those moths, Neil has found that the insects developed types of “stealth coating” that serve as acoustic camouflage to evade hungry bats.

Neil will describe his work during the Acoustical Society of America’s 176th Meeting, held in conjunction with the Canadian Acoustical Association’s 2018 Acoustics Week, Nov. 5-9 at the Victoria Conference Centre in Victoria, Canada.

In his presentation, Neil will focus on how fur on a moth’s thorax and wing joints provide acoustic stealth by reducing the echoes of these body parts from bat calls.

“Thoracic fur provides substantial acoustic stealth at all ecologically relevant ultrasonic frequencies,” said Neil, a researcher at Bristol University. “The thorax fur of moths acts as a lightweight porous sound absorber, facilitating acoustic camouflage and offering a significant survival advantage against bats.” Removing the fur from the moth’s thorax increased its detection risk by as much as 38 percent.

Neil used acoustic tomography to quantify echo strength in the spatial and frequency domains of two deaf moth species that are subject to bat predation and two butterfly species that are not.

In comparing the effects of removing thorax fur from insects that serve as food for bats to those that don’t, Neil’s research team found that thoracic fur determines acoustic camouflage of moths but not butterflies.

“We found that the fur on moths was both thicker and denser than that of the butterflies, and these parameters seem to be linked with the absorptive performance of their respective furs,” Neil said. “The thorax fur of the moths was able to absorb up to 85 percent of the impinging sound energy. The maximum absorption we found in butterflies was just 20 percent.”

Neil’s research could contribute to the development of biomimetic materials for ultrathin sound absorbers and other noise-control devices.

“Moth fur is thin and lightweight,” said Neil, “and acts as a broadband and multidirectional ultrasound absorber that is on par with the performance of current porous sound-absorbing foams.”

Moth fur? This has changed my view of moths although I reserve the right to get cranky when local moths chew through my wool sweaters. Here’s a link to and a citation for the paper,

Biomechanics of a moth scale at ultrasonic frequencies by Zhiyuan Shen, Thomas R. Neil, Daniel Robert, Bruce W. Drinkwater, and Marc W. Holderied. PNAS [Proccedings of the National Academy of Sciences of the United States of America] November 27, 2018 115 (48) 12200-12205; published ahead of print November 12, 2018 https://doi.org/10.1073/pnas.1810025115

This paper is behind a paywall.

Unusually I’m going to include the paper’s abstract here,

The wings of moths and butterflies are densely covered in scales that exhibit intricate shapes and sculptured nanostructures. While certain butterfly scales create nanoscale photonic effects [emphasis mine], moth scales show different nanostructures suggesting different functionality. Here we investigate moth-scale vibrodynamics to understand their role in creating acoustic camouflage against bat echolocation, where scales on wings provide ultrasound absorber functionality. For this, individual scales can be considered as building blocks with adapted biomechanical properties at ultrasonic frequencies. The 3D nanostructure of a full Bunaea alcinoe moth forewing scale was characterized using confocal microscopy. Structurally, this scale is double layered and endowed with different perforation rates on the upper and lower laminae, which are interconnected by trabeculae pillars. From these observations a parameterized model of the scale’s nanostructure was formed and its effective elastic stiffness matrix extracted. Macroscale numerical modeling of scale vibrodynamics showed close qualitative and quantitative agreement with scanning laser Doppler vibrometry measurement of this scale’s oscillations, suggesting that the governing biomechanics have been captured accurately. Importantly, this scale of B. alcinoe exhibits its first three resonances in the typical echolocation frequency range of bats, suggesting it has evolved as a resonant absorber. Damping coefficients of the moth-scale resonator and ultrasonic absorption of a scaled wing were estimated using numerical modeling. The calculated absorption coefficient of 0.50 agrees with the published maximum acoustic effect of wing scaling. Understanding scale vibroacoustic behavior helps create macroscopic structures with the capacity for broadband acoustic camouflage.

Those nanoscale photonic effects caused by butterfly scales are something I’d usually describe as optical effects due to the nanoscale structures on some butterfly wings, notably those of the Blue Morpho butterfly. In fact there’s a whole field of study on what’s known as structural colo(u)r. Strictly speaking I’m not sure you could describe the nanostructures on Glasswing butterflies as an example of structure colour since those structures make that butterfly’s wings transparent but they are definitely an optical effect. For the curious, you can use ‘blue morpho butterfly’, ‘glasswing butterfly’ or ‘structural colo(u)r’ to search for more on this blog or pursue bigger fish with an internet search.