Tag Archives: bioinspired

Enhance or weaken memory with stretchy, bioinspired synaptic transistor

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This news is intriguing since they usually want to enhance memory not weaken it. Interestingly, this October 3, 2022 news item on ScienceDaily doesn’t immediately answer why you might want to weaken memory,

Robotics and wearable devices might soon get a little smarter with the addition of a stretchy, wearable synaptic transistor developed by Penn State engineers. The device works like neurons in the brain to send signals to some cells and inhibit others in order to enhance and weaken the devices’ memories.

Led by Cunjiang Yu, Dorothy Quiggle Career Development Associate Professor of Engineering Science and Mechanics and associate professor of biomedical engineering and of materials science and engineering, the team designed the synaptic transistor to be integrated in robots or wearables and use artificial intelligence to optimize functions. The details were published on Sept. 29 [2022] in Nature Electronics.

“Mirroring the human brain, robots and wearable devices using the synaptic transistor can use its artificial neurons to ‘learn’ and adapt their behaviors,” Yu said. “For example, if we burn our hand on a stove, it hurts, and we know to avoid touching it next time. The same results will be possible for devices that use the synaptic transistor, as the artificial intelligence is able to ‘learn’ and adapt to its environment.”

…

A September 29, 2022 Pennsylvania State University (Penn State) news release (also on EurekAlert but published on October 3, 2022) by Mariah Chuprinski, which originated the news item, explains why you might want to weaken memory,

According to Yu, the artificial neurons in the device were designed to perform like neurons in the ventral tegmental area, a tiny segment of the human brain located in the uppermost part of the brain stem. Neurons process and transmit information by releasing neurotransmitters at their synapses, typically located at the neural cell ends. Excitatory neurotransmitters trigger the activity of other neurons and are associated with enhancing memories, while inhibitory neurotransmitters reduce the activity of other neurons and are associated with weakening memories.

“Unlike all other areas of the brain, neurons in the ventral tegmental area are capable of releasing both excitatory and inhibitory neurotransmitters at the same time,” Yu said. “By designing the synaptic transistor to operate with both synaptic behaviors simultaneously, fewer transistors are needed [emphasis mine] compared to conventional integrated electronics technology, which simplifies the system architecture and allows the device to conserve energy.”

To model soft, stretchy biological tissues, the researchers used stretchable bilayer semiconductor materials to fabricate the device, allowing it to stretch and twist while in use, according to Yu. Conventional transistors, on the other hand, are rigid and will break when deformed.

“The transistor is mechanically deformable and functionally reconfigurable, yet still retains its functions when stretched extensively,” Yu said. “It can attach to a robot or wearable device to serve as their outermost skin.”

In addition to Yu, other contributors include Hyunseok Shim and Shubham Patel, Penn State Department of Engineering Science and Mechanics; Yongcao Zhang, the University of Houston Materials Science and Engineering Program; Faheem Ershad, Penn State Department of Biomedical Engineering and University of Houston Department of Biomedical Engineering; Binghao Wang, School of Electronic Science and Engineering, Southeast University [Note: There’s one in Bangladesh, one in China, and there’s a Southeastern University in Florida, US] and Department of Chemistry and the Materials Research Center, Northwestern University; Zhihua Chen, Flexterra Inc.; Tobin J. Marks, Department of Chemistry and the Materials Research Center, Northwestern University; Antonio Facchetti, Flexterra Inc. and Northwestern University’s Department of Chemistry and Materials Research Center.

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

An elastic and reconfigurable synaptic transistor based on a stretchable bilayer semiconductor by Hyunseok Shim, Faheem Ershad, Shubham Patel, Yongcao Zhang, Binghao Wang, Zhihua Chen, Tobin J. Marks, Antonio Facchetti & Cunjiang Yu. Nature Electronics (2022) DOI: DOI: https://doi.org/10.1038/s41928-022-00836-5 Published: 29 September 2022

This paper is behind a paywall.

One of world’s most precise microchip sensors thanks to nanotechnology, machine learning, extended cognition, and spiderwebs

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I love science stories about the inspirational qualities of spiderwebs. A November 26, 2021 news item on phys.org describes how spiderwebs have inspired advances in sensors and, potentially, quantum computing,,

A team of researchers from TU Delft [Delft University of Technology; Netherlands] managed to design one of the world’s most precise microchip sensors. The device can function at room temperature—a ‘holy grail’ for quantum technologies and sensing. Combining nanotechnology and machine learning inspired by nature’s spiderwebs, they were able to make a nanomechanical sensor vibrate in extreme isolation from everyday noise. This breakthrough, published in the Advanced Materials Rising Stars Issue, has implications for the study of gravity and dark matter as well as the fields of quantum internet, navigation and sensing.

Inspired by nature’s spider webs and guided by machine learning, Richard Norte (left) and Miguel Bessa (right) demonstrate a new type of sensor in the lab. [Photography: Frank Auperlé]

A November 24, 2021 TU Delft press release (also on EurekAlert but published on November 23, 2021), which originated the news item, describes the research in more detail,

One of the biggest challenges for studying vibrating objects at the smallest scale, like those used in sensors or quantum hardware, is how to keep ambient thermal noise from interacting with their fragile states. Quantum hardware for example is usually kept at near absolute zero (−273.15°C) temperatures, with refrigerators costing half a million euros apiece. Researchers from TU Delft created a web-shaped microchip sensor which resonates extremely well in isolation from room temperature noise. Among other applications, their discovery will make building quantum devices much more affordable.

Hitchhiking on evolution
Richard Norte and Miguel Bessa, who led the research, were looking for new ways to combine nanotechnology and machine learning. How did they come up with the idea to use spiderwebs as a model? Richard Norte: “I’ve been doing this work already for a decade when during lockdown, I noticed a lot of spiderwebs on my terrace. I realised spiderwebs are really good vibration detectors, in that they want to measure vibrations inside the web to find their prey, but not outside of it, like wind through a tree. So why not hitchhike on millions of years of evolution and use a spiderweb as an initial model for an ultra-sensitive device?” 

Since the team did not know anything about spiderwebs’ complexities, they let machine learning guide the discovery process. Miguel Bessa: “We knew that the experiments and simulations were costly and time-consuming, so with my group we decided to use an algorithm called Bayesian optimization, to find a good design using few attempts.” Dongil Shin, co-first author in this work, then implemented the computer model and applied the machine learning algorithm to find the new device design. 

Microchip sensor based on spiderwebs
To the researcher’s surprise, the algorithm proposed a relatively simple spiderweb out of 150 different spiderweb designs, which consists of only six strings put together in a deceivingly simple way. Bessa: “Dongil’s computer simulations showed that this device could work at room temperature, in which atoms vibrate a lot, but still have an incredibly low amount of energy leaking in from the environment – a higher Quality factor in other words. With machine learning and optimization we managed to adapt Richard’s spider web concept towards this much better quality factor.”

Based on this new design, co-first author Andrea Cupertino built a microchip sensor with an ultra-thin, nanometre-thick film of ceramic material called Silicon Nitride. They tested the model by forcefully vibrating the microchip ‘web’ and measuring the time it takes for the vibrations to stop. The result was spectacular: a record-breaking isolated vibration at room temperature. Norte: “We found almost no energy loss outside of our microchip web: the vibrations move in a circle on the inside and don’t touch the outside. This is somewhat like giving someone a single push on a swing, and having them swing on for nearly a century without stopping.”

Implications for fundamental and applied sciences
With their spiderweb-based sensor, the researchers’ show how this interdisciplinary strategy opens a path to new breakthroughs in science, by combining bio-inspired designs, machine learning and nanotechnology. This novel paradigm has interesting implications for quantum internet, sensing, microchip technologies and fundamental physics: exploring ultra-small forces for example, like gravity or dark matter which are notoriously difficult to measure. According to the researchers, the discovery would not have been possible without the university’s Cohesion grant, which led to this collaboration between nanotechnology and machine learning.

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

Spiderweb Nanomechanical Resonators via Bayesian Optimization: Inspired by Nature and Guided by Machine Learning by Dongil Shin, Andrea Cupertino, Matthijs H. J. de Jong, Peter G. Steeneken, Miguel A. Bessa, Richard A. Norte. Advanced Materials Volume34, Issue3 January 20, 2022 2106248 DOI: https://doi.org/10.1002/adma.202106248 First published (online): 25 October 2021

This paper is open access.

If spiderwebs can be sensors, can they also think?

it’s called ‘extended cognition’ or ‘extended mind thesis’ (Wikipedia entry) and the theory holds that the mind is not solely in the brain or even in the body. Predictably, the theory has both its supporters and critics as noted in Joshua Sokol’s article “The Thoughts of a Spiderweb” originally published on May 22, 2017 in Quanta Magazine (Note: Links have been removed),

Millions of years ago, a few spiders abandoned the kind of round webs that the word “spiderweb” calls to mind and started to focus on a new strategy. Before, they would wait for prey to become ensnared in their webs and then walk out to retrieve it. Then they began building horizontal nets to use as a fishing platform. Now their modern descendants, the cobweb spiders, dangle sticky threads below, wait until insects walk by and get snagged, and reel their unlucky victims in.

In 2008, the researcher Hilton Japyassú prompted 12 species of orb spiders collected from all over Brazil to go through this transition again. He waited until the spiders wove an ordinary web. Then he snipped its threads so that the silk drooped to where crickets wandered below. When a cricket got hooked, not all the orb spiders could fully pull it up, as a cobweb spider does. But some could, and all at least began to reel it in with their two front legs.

Their ability to recapitulate the ancient spiders’ innovation got Japyassú, a biologist at the Federal University of Bahia in Brazil, thinking. When the spider was confronted with a problem to solve that it might not have seen before, how did it figure out what to do? “Where is this information?” he said. “Where is it? Is it in her head, or does this information emerge during the interaction with the altered web?”

In February [2017], Japyassú and Kevin Laland, an evolutionary biologist at the University of Saint Andrews, proposed a bold answer to the question. They argued in a review paper, published in the journal Animal Cognition, that a spider’s web is at least an adjustable part of its sensory apparatus, and at most an extension of the spider’s cognitive system.

This would make the web a model example of extended cognition, an idea first proposed by the philosophers Andy Clark and David Chalmers in 1998 to apply to human thought. In accounts of extended cognition, processes like checking a grocery list or rearranging Scrabble tiles in a tray are close enough to memory-retrieval or problem-solving tasks that happen entirely inside the brain that proponents argue they are actually part of a single, larger, “extended” mind.

Among philosophers of mind, that idea has racked up citations, including supporters and critics. And by its very design, Japyassú’s paper, which aims to export extended cognition as a testable idea to the field of animal behavior, is already stirring up antibodies among scientists. …

It seems there is no definitive answer to the question of whether there is an ‘extended mind’ but it’s an intriguing question made (in my opinion) even more so with the spiderweb-inspired sensors from TU Delft.

Lobster-inspired 3D printed concrete

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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.

Optical fibers made from marine algae

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Apparently after you’ve finished imaging with your marine algae-based optical fibers, you can eat them. A July 24, 2020 news item on Nanowerk announces the new research,

An optical fiber made of agar has been produced at the University of Campinas (UNICAMP) in the state of São Paulo, Brazil. This device is edible, biocompatible and biodegradable. It can be used in vivo for body structure imaging, localized light delivery in phototherapy or optogenetics (e.g., stimulating neurons with light to study neural circuits in a living brain), and localized drug delivery.

Another possible application is the detection of microorganisms in specific organs, in which case the probe would be completely absorbed by the body after performing its function.

…

Caption: Edible, biocompatible and biodegradable, these fibers have potential for various medical applications. Credit: Eric Fujiwara

A July 24, 2020 Fundação de Amparo à Pesquisa dFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) do Estado de São Paulo press release on EurekAlert, which originated the news item, provides a few more details about the researches and the work,

The research project, which was supported by São Paulo Research Foundation – FAPESP, was led by Eric Fujiwara, a professor in UNICAMP’s School of Mechanical Engineering, and Cristiano Cordeiro, a professor in UNICAMP’s Gleb Wataghin Institute of Physics, in collaboration with Hiromasa Oku, a professor at Gunma University in Japan.

An article on the study is published) in Scientific Reports, an online journal owned by Springer Nature.

Agar, also called agar-agar, is a natural gelatin obtained from marine algae. Its composition consists of a mixture of two polysaccharides, agarose and agaropectin. “Our optical fiber is an agar cylinder with an external diameter of 2.5 millimeters [mm] and a regular inner arrangement of six 0.5 mm cylindrical airholes around a solid core. Light is confined owing to the difference between the refraction indices of the agar core and the airholes,” Fujiwara told.

“To produce the fiber, we poured food-grade agar into a mold with six internal rods placed lengthwise around the main axis,” he continued. “The gel distributes itself to fill the available space. After cooling, the rods are removed to form airholes, and the solidified waveguide is released from the mold. The refraction index and geometry of the fiber can be adapted by varying the composition of the agar solution and mold design, respectively.”

The researchers tested the fiber in different media, from air and water to ethanol and acetone, concluding that it is context-sensitive. “The fact that the gel undergoes structural changes in response to variations in temperature, humidity and pH makes the fiber suitable for optical sensing,” Fujiwara said.

Another promising application is its simultaneous use as an optical sensor and a growth medium for microorganisms. “In this case, the waveguide can be designed as a disposable sample unit containing the necessary nutrients. The immobilized cells in the device would be optically sensed, and the signal would be analyzed using a camera or spectrometer,” he said.

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About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at http://www.fapesp.br/en and visit FAPESP news agency at http://www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

As per my usual practice, here’s a link to and a citation for the paper,

Agarose-based structured optical fibre by Eric Fujiwara, Thiago D. Cabral, Miko Sato, Hiromasa Oku & Cristiano M. B. Cordeiro. Scientific Reports volume 10, Article number: 7035 (2020) DOI: https://doi.org/10.1038/s41598-020-64103-3 Published: 27 April 2020

This paper is open access.

Should you have a problem accessing the English language version of the FAPESP website, the Portuguese language version of the site seems more accessible (assuming you have the language skills).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This paper is open access.

Why the high hopes?

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

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

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

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

Bacterial cellulose nanofibers made strong and tough

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

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

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

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

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

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

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

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

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

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

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

This paper appears to be open access.

Beautiful solar cells based on insect eyes

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What a gorgeous image!

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

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

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

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

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

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

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

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

Eye of the fly

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

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

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

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

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

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

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

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

Durability

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

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

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

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

Researchers have also made this image available,

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

Not quite as weirdly beautiful as the insect eyes.

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

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

This paper is behind a paywall.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This paper is behind a paywall.

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

A nano fabrication technique used to create next generation heart valve

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

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

From a May 18, 2017 news item on ScienceDaily,

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

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

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

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

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

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

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

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

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

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

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

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

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

This paper is behind a paywall.