An intriguing field, and why not a thread?
A new ceramic which will probably soon be coming to a device near you . . .
"Researchers develop thermoformable ceramics, 'a new frontier in materials'" |
Phys.org (https://phys.org/news/2022-10-thermoformable-ceramics-frontier-materials.html)
QuoteIt was one of those happy accidents of science. Northeastern professor Randall Erb and Ph.D. student Jason Bice were working on a product for a university client—and wound up with an entirely new class of material.
Their discovery of an all-ceramic that can be compression-molded into complex parts—an industry breakthrough—could transform the design and construction of heat-emitting electronics, including cellphones and other radio components.
"Our research group's lives are very much situated at the bleeding edge of technology," says Erb, an associate professor of mechanical and industrial engineering who heads the DAPS Lab at Northeastern. "Things break a lot, and every once in a while one of those breaks turns out to be good fortune."
Last July, Erb was in his Northeastern lab with Bice, who has since earned a mechanical engineering Ph.D. They were testing an experimental ceramic compound as part of a hypersonic project for an industrial partner when something appeared to go wrong.
"We blasted it with a blowtorch and, while we were loading it, it unexpectedly deformed and fell out of the fixture," Erb says. "We looked at the sample on the floor thinking that it was a failure."
Closer examination gave way to a revelation.
"We realized it was perfectly intact," Erb says. "It was just shaped differently."
[Continues . . . (https://phys.org/news/2022-10-thermoformable-ceramics-frontier-materials.html)]
Thanks for that interesting link. So many important discoveries are the result of happy accidents. First class scientists are open minded and alert, so they notice interesting results in "failed" experiments. The accidental discovery of mauveine by Perkin when he was in his tens is a classic example.
https://www.vox.com/science-and-health/2018/3/12/17109258/sir-william-henry-perkin-google-doodle-birthday-180-mauveine-purple-dye (https://www.vox.com/science-and-health/2018/3/12/17109258/sir-william-henry-perkin-google-doodle-birthday-180-mauveine-purple-dye)
This one is cool; a new material composed of bosons.
"Scientists Discover a Weird Material Made of Subatomic Particles" |
Science Alert (https://www.sciencealert.com/scientists-discover-a-weird-material-made-of-subatomic-particles)
QuoteScientists are always looking for the next weird and wonderful material, and they've just found it: A bosonic correlated insulator to give it its technical name, which is both a new material and, indeed, a whole new state of matter.
It's a lattice formed from a layer of tungsten diselenide and a layer of tungsten disulfide placed on top of each other but not fully aligned.
That slight misalignment creates what's known as a moiré pattern, and here has revealed some interesting properties.
To understand what's special about the material, you need to understand what bosons and fermions are. At the quantum level, particles are grouped into two main types: bosons (force carriers like photons) that can share the same quantum state, and fermions (matter particles like electrons), which can't. Usually, fermions are easier to work with.
"Conventionally, people have spent most of their efforts to understand what happens when you put many fermions together," says condensed matter physicist Chenhao Jin from the University of California, Santa Barbara (UCSB).
"The main thrust of our work is that we basically made a new material out of interacting bosons."
[Continues . . . (https://www.sciencealert.com/scientists-discover-a-weird-material-made-of-subatomic-particles)]
The paper (https://www.science.org/doi/10.1126/science.add5574) is behind a paywall.
QuoteAbstract:
A panoply of unconventional electronic states has been observed in moiré superlattices. Engineering similar bosonic phases remains, however, largely unexplored.
We report the observation of a bosonic correlated insulator in tungsten diselenide/tungsten disulfide (WSe2/WS2) moiré superlattices composed of excitons, that is, tightly bound electron-hole pairs. We develop a pump probe spectroscopy method that we use to observe an exciton incompressible state at exciton filling νex = 1 and charge neutrality, indicating a correlated insulator of excitons.
With varying charge density, the bosonic correlated insulator continuously transitions into an electron correlated insulator at charge filling νe = 1, suggesting a mixed correlated insulating state between the two limits. Our studies establish semiconducting moiré superlattices as an intriguing platform for engineering bosonic phases.
My mind is officially blown!
Quote from: Tank on June 20, 2023, 08:48:41 PMMy mind is officially blown!
Yeah, I got a little frisson myself when I read the article. ;D
Quote from: hermes2015 on October 14, 2022, 04:08:24 AMThanks for that interesting link. So many important discoveries are the result of happy accidents. First class scientists are open minded and alert, so they notice interesting results in "failed" experiments. The accidental discovery of mauveine by Perkin when he was in his tens is a classic example.
https://www.vox.com/science-and-health/2018/3/12/17109258/sir-william-henry-perkin-google-doodle-birthday-180-mauveine-purple-dye (https://www.vox.com/science-and-health/2018/3/12/17109258/sir-william-henry-perkin-google-doodle-birthday-180-mauveine-purple-dye)
Missed this first time around--thanks in return for your link! Interesting that our idea of mauve is distinctly different from the color produced by the original dye. I did a bit of further looking and learned that Perkin's original mauve fades fairly quickly, which may have something to do with it. I had always thought the 1890s being the "Mauve Decade" referred to the more subdued tone, but perhaps not. :)
Here is another important development aimed at heat mitigation.
Quote from: Icarus on July 28, 2023, 12:07:36 AMHere is another important development aimed at heat mitigation.
Ah, hoping you still have the link for that video,
Icarus. Sounds intriguing.
I can't see it either. What was the subject.
Purdue University engineering school has developed a white paint that can reject a huge proportion of th suns heat. It is different from ordinary white paint which might be capable of rejecting nine percent of the heat. The new paint can reject something on the order of ninety percent. Something about the way that the particulate matter is distributed and variously sized in the paint.
I will root around on the internet and see if I can find the descriptive article. By now, if this is for real, the report will appear in various scientific journals.
That is not the one that I tried to post.
This one is detailed beyond need for the casual viewer. I did watch the whole deal and managed to recall some of the chemistry that I had long forgotten.
In any case, the end product may well be important for our survival. Imagine that most of the worlds roofs were coated with this stuff. Air conditioners would not run so much. That would reduce the demand for electricity, thus reduce the carbon output of the generating facilities, affect the world economy and more.
Thanks for the help Hermes.
I think I read about this a few months ago. Still worthwhile for this thread.
"We Finally Know How Ancient Roman Concrete Was Able to Last Thousands of Years" |
Science Alert (https://www.sciencealert.com/we-finally-know-how-ancient-roman-concrete-was-able-to-last-thousands-of-years)
QuoteThe ancient Romans were masters of building and engineering, perhaps most famously represented by the aqueducts. And those still functional marvels rely on a unique construction material: pozzolanic concrete, a spectacularly durable concrete that gave Roman structures their incredible strength.
Even today, one of their structures – the Pantheon, still intact and nearly 2,000 years old – holds the record for the world's largest dome of unreinforced concrete.
The properties of this concrete have generally been attributed to its ingredients: pozzolana, a mix of volcanic ash – named after the Italian city of Pozzuoli, where a significant deposit of it can be found – and lime. When mixed with water, the two materials can react to produce strong concrete.
But that, as it turns out, is not the whole story. In 2023, an international team of researchers led by the Massachusetts Institute of Technology (MIT) found that not only are the materials slightly different from what we may have thought, but the techniques used to mix them were also different.
The smoking guns were small, white chunks of lime that can be found in what seems to be otherwise well-mixed concrete. The presence of these chunks had previously been attributed to poor mixing or materials, but that did not make sense to materials scientist Admir Masic of MIT.
"The idea that the presence of these lime clasts was simply attributed to low quality control always bothered me," Masic said back in January 2023.
"If the Romans put so much effort into making an outstanding construction material, following all of the detailed recipes that had been optimized over the course of many centuries, why would they put so little effort into ensuring the production of a well-mixed final product? There has to be more to this story."
Masic and the team, led by MIT civil engineer Linda Seymour, carefully studied 2,000-year-old samples of Roman concrete from the archaeological site of Privernum in Italy. These samples were subjected to large-area scanning electron microscopy and energy-dispersive x-ray spectroscopy, powder X-ray diffraction, and confocal Raman imaging to gain a better understanding of the lime clasts.
One of the questions in mind was the nature of the lime used. The standard understanding of pozzolanic concrete is that it uses slaked lime. First, limestone is heated at high temperatures to produce a highly reactive caustic powder called quicklime, or calcium oxide.
Mixing quicklime with water produces slaked lime, or calcium hydroxide: a slightly less reactive, less caustic paste. According to theory, it was this slaked lime that ancient Romans mixed with the pozzolana.
Based on the team's analysis, the lime clasts in their samples are not consistent with this method. Rather, Roman concrete was probably made by mixing the quicklime directly with the pozzolana and water at extremely high temperatures, by itself or in addition to slaked lime, a process the team calls "hot mixing" that results in the lime clasts.
"The benefits of hot mixing are twofold," Masic said.
"First, when the overall concrete is heated to high temperatures, it allows chemistries that are not possible if you only used slaked lime, producing high-temperature-associated compounds that would not otherwise form. Second, this increased temperature significantly reduces curing and setting times since all the reactions are accelerated, allowing for much faster construction."
And it has another benefit: The lime clasts give the concrete remarkable self-healing abilities.
When cracks form in the concrete, they preferentially travel to the lime clasts, which have a higher surface area than other particles in the matrix. When water gets into the crack, it reacts with the lime to form a solution rich in calcium that dries and hardens as calcium carbonate, gluing the crack back together and preventing it from spreading further.
[Continues . . . (https://www.sciencealert.com/we-finally-know-how-ancient-roman-concrete-was-able-to-last-thousands-of-years)]
The paper is open source:
"Hot mixing: Mechanistic insights into the durability of ancient Roman concrete" |
Science Advances (https://www.science.org/doi/10.1126/sciadv.add1602)
QuoteAbstract:
Ancient Roman concretes have survived millennia, but mechanistic insights into their durability remain an enigma. Here, we use a multiscale correlative elemental and chemical mapping approach to investigating relict lime clasts, a ubiquitous and conspicuous mineral component associated with ancient Roman mortars.
Together, these analyses provide new insights into mortar preparation methodologies and provide evidence that the Romans employed hot mixing, using quicklime in conjunction with, or instead of, slaked lime, to create an environment where high surface area aggregate-scale lime clasts are retained within the mortar matrix.
Inspired by these findings, we propose that these macroscopic inclusions might serve as critical sources of reactive calcium for long-term pore and crack-filling or post-pozzolanic reactivity within the cementitious constructs. The subsequent development and testing of modern lime clast–containing cementitious mixtures demonstrate their self-healing potential, thus paving the way for the development of more durable, resilient, and sustainable concrete formulations.
Wow :)
Missed this one the first time around. May be an early inkling of an important development, or maybe not.
"A Cracked Piece of Metal Healed Itself in Experiment That Stunned Scientists" |
Science Alert (https://www.sciencealert.com/a-cracked-piece-of-metal-healed-itself-in-experiment-that-stunned-scientists)
QuoteIn a study published last year, a team from Sandia National Laboratories and Texas A&M University was testing the resilience of the metal, using a specialized transmission electron microscope technique to pull the ends of the metal 200 times every second.
They then observed the self-healing at ultra-small scales in a 40-nanometer-thick piece of platinum suspended in a vacuum.
Cracks caused by the kind of strain described above are known as fatigue damage: repeated stress and motion that causes microscopic breaks, eventually causing machines or structures to break.
Amazingly, after about 40 minutes of observation, the crack in the platinum started to fuse back together and mend itself before starting again in a different direction.
[. . .]
While the observation is unprecedented, it's not wholly unexpected. In 2013, Texas A&M University materials scientist Michael Demkowicz worked on a study predicting that this kind of nanocrack healing could happen, driven by the tiny crystalline grains inside metals essentially shifting their boundaries in response to stress.
Demkowicz also worked on this study, using updated computer models to show that his decade-old theories about metal's self-healing behavior at the nanoscale matched what was happening here.
That the automatic mending process happened at room temperature is another promising aspect of the research. Metal usually requires lots of heat to shift its form, but the experiment was carried out in a vacuum; it remains to be seen whether the same process will happen in conventional metals in a typical environment.
A possible explanation involves a process known as cold welding, which occurs under ambient temperatures whenever metal surfaces come close enough together for their respective atoms to tangle together.
Typically, thin layers of air or contaminants interfere with the process; in environments like the vacuum of space, pure metals can be forced close enough together to literally stick.
[Continues . . . (https://www.sciencealert.com/a-cracked-piece-of-metal-healed-itself-in-experiment-that-stunned-scientists)]
The paper (https://www.nature.com/articles/s41586-023-06223-0) is behind a paywall.
QuoteAbstract:
Fatigue in metals involves gradual failure through incremental propagation of cracks under repetitive mechanical load. In structural applications, fatigue accounts for up to 90% of in-service failure. Prevention of fatigue relies on implementation of large safety factors and inefficient overdesign. In traditional metallurgical design for fatigue resistance, microstructures are developed to either arrest or slow the progression of cracks. Crack growth is assumed to be irreversible. By contrast, in other material classes, there is a compelling alternative based on latent healing mechanisms and damage reversal.
Here, we report that fatigue cracks in pure metals can undergo intrinsic self-healing. We directly observe the early progression of nanoscale fatigue cracks, and as expected, the cracks advance, deflect and arrest at local microstructural barriers. However, unexpectedly, cracks were also observed to heal by a process that can be described as crack flank cold welding induced by a combination of local stress state and grain boundary migration.
The premise that fatigue cracks can autonomously heal in metals through local interaction with microstructural features challenges the most fundamental theories on how engineers design and evaluate fatigue life in structural materials. We discuss the implications for fatigue in a variety of service environments.
While the previous item shows an intriguing possibility for materials science, this one is just cool, in my opinion.
"Radical Theory Suggests Earthquakes Spark Gold Nuggets Into Existence" |
Science Alert (https://www.sciencealert.com/radical-theory-suggests-earthquakes-spark-gold-nuggets-into-existence)
QuoteNew findings by scientists in Australia could challenge what we thought we knew about the way gold nuggets bloom in vast reefs beneath our feet.
Under pressures of hundreds of megapascals (tens of thousands of pounds per square inch) and boiling hot temperatures, water squeezed up from the depths of Earth's crust carries dissolved gases, metals, and minerals to the surface with every quake and shudder of a seismic event.
As any good prospector knows, buried seams of crystalized silicon dioxide – better known as quartz – are fertile ground for gold mining, with both materials precipitating out of solution under strikingly similar conditions.
Though the basic mechanisms behind the precious ore's formation have been understood for some time, certain details have never quite added up, and new research from scientists at Australia's Monash University, the CSIRO, and the Australian Nuclear Science and Technology Organisation challenge the conventional views on how gold forms.
[. . .]
Silicon dioxide is an incredibly unique material. Where other crystals are relatively symmetrical, quartz forms with a bias that produces a voltage when stressed – a phenomenon known as the piezoelectric effect.
With every tremor of Earth's crust, seams of quartz will crackle with static currents as voltages emerge and electrons rebalance.
This charge jump is unlikely to move very far given quartz is an insulating material. Gold, on the other hand, is a great conductor of electricity, raising the possibility that electrochemical reactions within quartz seams might serve as a catalyst, drawing sufficient gold from solution in concentrated spots through repeated cycles of tiny shakes.
[. . .]
What was simulated in the lab using concentrated solutions and extensive periods of shaking would of course take far longer in the real world with dilute solutions and occasional tremors.
On geological timescales, however, the process could be relatively rapid. Without the added zap of stressed quartz, it's difficult to even explain how gold might accumulate in such rich deposits in the first place.
[Continues . . . (https://www.sciencealert.com/radical-theory-suggests-earthquakes-spark-gold-nuggets-into-existence)]
The paper (https://www.nature.com/articles/s41561-024-01514-1) is behind a paywall.
QuoteAbstract:
Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg kg−1 gold), hot, water ± carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry.
However, the widespread occurrence of large gold nuggets is at odds with the dilute nature of these fluids and the chemical inertness of quartz. Quartz is the only abundant piezoelectric mineral on Earth, and the cyclical nature of earthquake activity that drives orogenic gold deposit formation means that quartz crystals in veins will experience thousands of episodes of deviatoric stress.
Here we use quartz deformation experiments and piezoelectric modelling to investigate whether piezoelectric discharge from quartz can explain the ubiquitous gold–quartz association and the formation of gold nuggets. We find that stress on quartz crystals can generate enough voltage to electrochemically deposit aqueous gold from solution as well as accumulate gold nanoparticles.
Nucleation of gold via piezo-driven reactions is rate-limiting because quartz is an insulator; however, since gold is a conductor, our results show that existing gold grains are the focus of ongoing growth. We suggest this mechanism can help explain the creation of large nuggets and the commonly observed highly interconnected gold networks within quartz vein fractures.
Direct observation of palladium acting as a catalyst to synthesize water.
"Watch The Smallest Water Droplet Ever Seen Grow, Molecule by Molecule" |
Science Alert (https://www.sciencealert.com/watch-the-smallest-water-droplet-ever-seen-grow-molecule-by-molecule)
Quote
We all know the ingredients for water. You take two atoms of hydrogen and one of oxygen, moosh them together just so, and voila – you have a molecule of the most important compound to life on Earth.
Now, for the first time, scientists have observed this process in action up close. In real-time, and on a molecular scale, materials scientist Vinayak Dravid of Northwestern University and his colleagues watched as the tiniest bubble of water ever seen bloomed seemingly out of thin air.
How did they do it? By harnessing the strange powers of palladium, a metal that is known to catalyze the two elements to synthesize water.
"Think of Matt Damon's character, Mark Watney, in the movie The Martian," Dravid says. "He burned rocket fuel to extract hydrogen and then added oxygen from his oxygenator. Our process is analogous, except we bypass the need for fire and other extreme conditions. We simply mixed palladium and gasses together."
We've known about palladium's strange ability to synthesize significant amounts of water in a relatively short amount of time. But how exactly it works has been tricky to pin down. This is because it's hard to observe the process on the scales at which it occurs.
"You really need to be able to combine the direct visualization of water generation and the structure analysis at the atomic scale in order to figure out what's happening," explains materials scientist Yukun Liu of Northwestern University.
To overcome this significant obstacle, the team developed a membrane that traps molecules inside tiny, hexagonal nanoreactor cells. This makes it easier to image molecular processes using transmission electron microscopy, down to the nanometer scale.
Even so, the researchers were not sure that their attempt to directly observe the palladium reaction would be successful. They added hydrogen and oxygen atoms to the surface of a 20 nanometer-wide piece of palladium, and used their membrane to capture the ensuing interaction.
A single water molecule is less than a third of a nanometer across, while the atoms they consist of are far, far smaller. To 'see' the bonding of these tiny compounds, the researchers used a form of electron microscopy that recorded energy lost by scattering electrons.
[Continues . . . (https://www.sciencealert.com/watch-the-smallest-water-droplet-ever-seen-grow-molecule-by-molecule)]
The paper (https://www.pnas.org/doi/10.1073/pnas.2408277121) is behind a paywall.
QuoteAbstract:
Palladium (Pd) catalysts have been extensively studied for the direct synthesis of H2O through the hydrogen oxidation reaction at ambient conditions. This heterogeneous catalytic reaction not only holds considerable practical significance but also serves as a classical model for investigating fundamental mechanisms, including adsorption and reactions between adsorbates.
Nonetheless, the governing mechanisms and kinetics of its intermediate reaction stages under varying gas conditions remain elusive. This is attributed to the intricate interplay between adsorption, atomic diffusion, and concurrent phase transformation of catalyst. Herein, the Pd-catalyzed, water-forming hydrogen oxidation is studied in situ, to investigate intermediate reaction stages via gas cell transmission electron microscopy.
The dynamic behaviors of water generation, associated with reversible palladium hydride formation, are captured in real time with a nanoscale spatial resolution. Our findings suggest that the hydrogen oxidation rate catalyzed by Pd is significantly affected by the sequence in which gases are introduced. Through direct evidence of electron diffraction and density functional theory calculation, we demonstrate that the hydrogen oxidation rate is limited by precursors' adsorption. These nanoscale insights help identify the optimal reaction conditions for Pd-catalyzed hydrogen oxidation, which has substantial implications for water production technologies. The developed understanding also advocates a broader exploration of analogous mechanisms in other metal-catalyzed reactions.
Rec you do contribute some thoroughly fascinating posts. Thank you for periodically :toff: elevating my mind for at least a few minutes of time.
:toff:
Quote from: Icarus on October 26, 2024, 01:09:00 AMRec you do contribute some thoroughly fascinating posts. Thank you for periodically :toff: elevating my mind for at least a few minutes of time.
:toff:
Hear hear!
Quote from: Icarus on October 26, 2024, 01:09:00 AMRec you do contribute some thoroughly fascinating posts. Thank you for periodically :toff: elevating my mind for at least a few minutes of time.
:toff:
It's my pleasure,
Icarus and
Tank! I know that though the science posts may not stimulate a lot of discussion, they can be interesting to members of this site. I appreciate your appreciation. :) :toff:
You're no slouches when it comes to the thought-provoking department. I'm still reading that
New Yorker article about various election interference efforts by non-US entities, for instance.
A couple of good items for this thread today.
"Living Material Made From Blood Can Repair Bones, Study Shows" |
Science Alert (https://www.sciencealert.com/living-material-made-from-blood-can-repair-bones-study-shows)
QuoteWhen skin tissue is wounded, our blood starts clotting as part of the healing process. Scientists have now developed a blood-based implant that supercharges this mechanism for bigger repair projects: broken bones.
The international team of researchers behind the implant calls it a "biocooperative regenerative" material: it uses synthetic peptides to improve the structure and function of the barrier naturally formed by blood when it clots.
In tests on rats, the gel-like substance – which can be 3D-printed – was effective in repairing bone damage. If this can be adapted and scaled up for human use, it has huge potential as a way of boosting the body's natural healing processes.
[. . .]
A key component of clotting blood is the solid regenerative hematoma (RH), and this was the main focus of the research. Custom molecules called peptide amphiphiles (PAs) were developed in the lab, which help guide and enhance what the RH does naturally.
When added to human blood, these molecules safely ramped up the clotting process. The researchers were able to get the nanofibers of the PAs to link with the scaffolding of the RH, for example, guiding the creation of stronger structures.
Using PAs added to the animal's own blood to create the material, the team was able to successfully repair small bone defects in the skulls of rats.
Different types of cells that are key to the repair process – including mesenchymal stromal cells, endothelial cells, and fibroblasts (which help form connective tissue) – were observed to be active in the new implant material.
[Continues . . . (https://www.sciencealert.com/living-material-made-from-blood-can-repair-bones-study-shows)]
The paper is open access:
"Biocooperative Regenerative Materials by Harnessing Blood-Clotting and Peptide Self-Assembly" |
Advanced Materials (https://onlinelibrary.wiley.com/doi/10.1002/adma.202407156)
QuoteAbstract:
The immune system has evolved to heal small ruptures and fractures with remarkable efficacy through regulation of the regenerative hematoma (RH); a rich and dynamic environment that coordinates numerous molecular and cellular processes to achieve complete repair. Here, a biocooperative approach that harnesses endogenous molecules and natural healing to engineer personalized regenerative materials is presented.
Peptide amphiphiles (PAs) are co-assembled with blood components during coagulation to engineer a living material that exhibits key compositional and structural properties of the RH. By exploiting non-selective and selective PA-blood interactions, the material can be immediately manipulated, mechanically-tuned, and 3D printed. The material preserves normal platelet behavior, generates and provides a continuous source of growth factors, and promotes in vitro growth of mesenchymal stromal cells, endothelial cells, and fibroblasts.
Furthermore, using a personalized autologous approach to convert whole blood into PA-blood gel implants, bone regeneration is shown in a critical-sized rat calvarial defect. This study provides proof-of-concept for a biocooperative approach that goes beyond biomimicry by using mechanisms that Nature has evolved to heal as tools to engineer accessible, personalized, and regenerative biomaterials that can be readily formed at point of use.
2nd item --
"Researchers develop new shape-changing polymer" |
EurekAlert (https://www.eurekalert.org/news-releases/1067435)
QuoteA team of scientists has created a new shape-changing polymer that could transform how future soft materials are constructed.
Made using a material called a liquid crystalline elastomer (LCE), a soft rubber-like material that can be stimulated by external forces like light or heat, the polymer is so versatile that it can move in several directions.
Its behavior, which resembles the movements of animals in nature, includes being able to twist, tilt left and right, shrink and expand, said Xiaoguang Wang, co-author of the study and an assistant professor in chemical and biomolecular engineering at The Ohio State University.
"Liquid crystals are materials that have very unique characteristics and properties that other materials cannot normally achieve," said Wang. "They're fascinating to work with."
This new polymer's ability to change shapes could make it useful for creating soft robots or artificial muscles, among other high-tech devices in medicine and other fields.
[Continues . . . (https://www.eurekalert.org/news-releases/1067435)]
The paper (https://www.science.org/doi/10.1126/science.adq6434) is behind a paywall.
QuoteAbstract:
Ambidirectionality, which is the ability of structural elements to move beyond a reference state in two opposite directions, is common in nature. However, conventional soft materials are typically limited to a single, unidirectional deformation unless complex hybrid constructs are used.
We exploited the combination of mesogen (https://en.wikipedia.org/wiki/Mesogen) self-assembly, polymer chain elasticity, and polymerization-induced stress to design liquid crystalline elastomers that exhibit two mesophases: chevron smectic (https://archive.is/eL4EH) C (cSmC) and smectic A (SmA).
Inducing the cSmC-SmA–isotropic phase transition led to an unusual inversion of the strain field in the microstructure, resulting in opposite deformation modes (e.g., consecutive shrinkage or expansion and right-handed or left-handed twisting and tilting in opposite directions) and high-frequency nonmonotonic oscillations. This ambidirectional movement is scalable and can be used to generate Gaussian transformations at the macroscale.
As a bonus, though I think this is more engineering than materials science, it's a neat item.
"Magnetically Controlled Kirigami Surfaces Move Objects: No Grasping Needed" |
NCSU News (https://news.ncsu.edu/2024/12/remote-control-kirigami-metasheets/)
QuoteResearchers have developed a novel device that couples magnetic fields and kirigami design principles to remotely control the movement of a flexible dimpled surface, allowing it to manipulate objects without actually grasping them – making it useful for lifting and moving items such as fragile objects, gels or liquids. The technology has potential for use in confined spaces, where robotic arms or similar tools aren't an option.
"We were trying to address two challenges here," says Jie Yin, co-corresponding author of a paper on the work and an associate professor of mechanical and aerospace engineering at North Carolina State University. "The first challenge was how to move objects that you can't pick up with grippers – such as fragile objects or things in confined spaces. The second challenge was how to use a magnetic field to remotely lift and move objects that are not magnetic."
To address those challenges, the researchers created a "metasheet" that consists of an elastic polymer that is embedded with magnetic microparticles. A pattern was then cut into the sheet. The outer edges of the metasheet are attached to a rigid frame.
By moving a magnetic field under the metasheet, you can force sections of the metasheet to bulge upward or sink downward.
"You can actually cause the surface of the metasheet to move like a wave by controlling the direction of the magnetic field," Yin says. "And adjusting the strength of the magnetic field determines how much the wave rise or fall."
[Continues . . . (https://news.ncsu.edu/2024/12/remote-control-kirigami-metasheets/)]
The paper is open access:
"Magnetic kirigami dome metasheet with high deformability and stiffness for adaptive dynamic shape-shifting and multimodal manipulation" |
Science Advances (https://www.science.org/doi/10.1126/sciadv.adr8421)
QuoteSoft shape-shifting materials offer enhanced adaptability in shape-governed properties and functionalities. However, once morphed, they struggle to reprogram their shapes and simultaneously bear loads for fulfilling multifunctionalities.
Here, we report a dynamic spatiotemporal shape-shifting kirigami dome metasheet with high deformability and stiffness that responds rapidly to dynamically changing magnetic fields. The magnetic kirigami dome exhibits over twice higher doming height and 1.5 times larger bending curvature, as well as sevenfold enhanced structural stiffness compared to its continuous counterpart without cuts. The metasheet achieves omnidirectional doming and multimodal translational and rotational wave-like shape-shifting, quickly responding to changing magnetic fields within 2 milliseconds.
Using the dynamic shape-shifting and adaptive interactions with objects, we demonstrate its applications in voxelated (https://en.wikipedia.org/wiki/Voxel) dynamic displays and remote magnetic multimodal directional and rotary manipulation of nonmagnetic objects without grasping. It shows high-load transportation ability of over 40 times its own weight, as well as versatility in handling objects of different materials (liquid and solid), sizes, shapes, and weights.
^ ^ Will wonders never cease? One would hope not.
Quote from: Icarus on December 09, 2024, 12:06:38 AM^ ^ Will wonders never cease? One would hope not.
Fully agree
Icarus! In the course of assembling that post I learned three new words. "Voxelated" I think I should have already known--a voxel is basically a three dimensional pixel. "Mesogen" (general descriptor of liquid crystal) and "smectic" (of, relating to, or being the phase of a liquid crystal characterized by arrangement of molecules in layers with the long molecular axes in a given layer being parallel to one another and those of other layers and perpendicular or slightly inclined to the plane of the layer) on the other hand, being more or less specific to the field of liquid crystal, are a bit more arcane.
Creating small-scale structures that interlock in interesting ways is apparently a branch of materials science. Previously I'd have considered it more an exercise in engineering of a sort, but then I'm not a materials scientist. As the article explains, creating this stuff at a molecular level was too much of a challenge so they scaled up. It remains to be seen whether that particular challenge can be overcome but they seem optimistic. In any case, they've produced some interesting stuff.
"Reimagining chain mail" |
Science Daily (https://www.sciencedaily.com/releases/2025/01/250121162100.htm)
QuoteExperiments from the Caltech lab of Chiara Daraio, G. Bradford Jones Professor of Mechanical Engineering and Applied Physics and Heritage Medical Research Institute Investigator, have yielded a fascinating new type of matter, neither granular nor crystalline, that responds to some stresses as a fluid would and to others like a solid. The new material, known as PAM (for polycatenated architected materials) could have uses in areas ranging from helmets and other protective gear to biomedical devices and robotics.
PAMs are not found in nature, though their basic form is known to us through the millennia-old manufacture of chain mail: small metal rings linked together to form a mesh, most often used as a flexible form of armor. PAMs, however, are like chain mail on steroids. Following the basic principle of interlocking shapes, like those found in a chain, PAMs are made up of a variety of shapes linked together to form three-dimensional patterns whose configurations are almost unimaginably variable. The resulting materials, which Daraio and her colleagues have rendered using 3D printers, exhibit behaviors not found in other types of materials.
Wenjie Zhou, postdoctoral scholar research associate in mechanical and civil engineering, has been working on these types of materials for two years in Daraio's lab. "I was a chemist, and I wanted to make these structures at a molecular scale, but that proved too challenging. In order to get answers to the questions I had about how these structures behave, I decided to join Chiara's group and study PAMs at a larger scale."
The PAMs that Daraio's group created and studied were first modeled on a computer and were designed to replicate lattice structures found in crystalline substances but with the crystal's fixed particles replaced by entangled rings or cages with multiple sides.
These lattices were then printed out three-dimensionally using a variety of materials, including acrylic polymers, nylon, and metals. Once the PAMs could be held in the palm of one's hand—most of the prototypes are 5-centimeter (2-inch) cubes or spheres with a 5-centimeter diameter—they were exposed to various types of physical stress. "We started with compression," Zhou explains, "compressing the objects a bit harder each time. Then we tried a simple shear, a lateral force, like what you would apply if you were trying to tear the material apart. Finally, we did rheology tests, seeing how the materials responded to twisting, first slowly and then more quickly and strongly."
In some scenarios, these PAMs behaved like liquids. "Imagine applying a shear stress to water," Zhou says. "There would be zero resistance. Because PAMs have all these coordinated degrees of freedom, with the rings and cages they are composed of sliding against one another as the links of a chain would, many have very little shear resistance." But when these structures are compressed, they may become fully rigid, behaving like solids.
This dynamism makes PAMs unique. "PAMs are really a new type of matter," Daraio says. "We all have a clear distinction in mind when we think of solid materials and granular matter. Solid materials are often described as crystalline lattices. This is what you see in the classic ball-and-stick models of atomic, chemical, or larger crystalline structures. It is these materials that have formed our conventional understanding of solid matter. The other class of materials is granular, as we see in substances like rice, flour, or ground coffee. These materials are made up of discrete particles, free to move and slide relative to one another."
PAMs defy this binary classification. "With PAMs, the individual particles are linked as they are in crystalline structures, and yet, because these particles are free to move relative to one another, they flow, they slide on top of each other, and they change their relative positions, more like grains of sand," Daraio explains. "PAMs can be very different from one another. You can print them in squishy materials or hard ones. You can change the shape of each particle, and you can change the lattice that you use to connect these particles. Each of these parameters affects the behavior of the resulting material. But all of them show a characteristic transition between fluid and solid-like behavior. This transition may happen under different circumstances, but it always happens."
[Continues . . . (https://www.sciencedaily.com/releases/2025/01/250121162100.htm)]
The paper (https://www.science.org/doi/10.1126/science.adr9713) is behind a paywall.
QuoteAbstract:
Architected materials derive their properties from the geometric arrangement of their internal structural elements. Their designs rely on continuous networks of members to control the global mechanical behavior of the bulk. In this study, we introduce a class of materials that consist of discrete concatenated rings or cage particles interlocked in three-dimensional networks, forming polycatenated architected materials (PAMs).
We propose a general design framework that translates arbitrary crystalline networks into particle concatenations and geometries. In response to small external loads, PAMs behave like non-Newtonian fluids, showing both shear-thinning and shear-thickening responses, which can be controlled by their catenation topologies.
At larger strains, PAMs behave like lattices and foams, with a nonlinear stress-strain relation. At microscale, we demonstrate that PAMs can change their shapes in response to applied electrostatic charges. The distinctive properties of PAMs pave the path for developing stimuli-responsive materials, energy-absorbing systems, and morphing architectures.
Complex pattern formation (multi-arm spirals, etc.) on a germanium crystal surface, apparently similar in origin to pattern formation in organisms.
"Serendipitous discovery reveals how stress and chemistry etch mysterious spiral patterns" |
Phys.org (https://phys.org/news/2025-03-serendipitous-discovery-reveals-stress-chemistry.html)
QuoteUCLA doctoral student Yilin Wong noticed that some tiny dots had appeared on one of her samples, which had been accidentally left out overnight. The layered sample consisted of a germanium wafer topped with evaporated metal films in contact with a drop of water. On a whim, she looked at the dots under a microscope and couldn't believe her eyes. Beautiful spiral patterns had been etched into the germanium surface by a chemical reaction.
Wong's curiosity led her on a journey to discover what no one had seen before: Hundreds of near-identical spiral patterns can spontaneously form on a centimeter square germanium chip. Moreover, small changes in experiment parameters, such as the thickness of the metal film, generated different patterns, including Archimedean spirals, logarithmic spirals, lotus flower shapes, radially symmetric patterns and more.
The discovery, published in Physical Review Materials, occurred fortuitously when Wong made a small mistake while attempting to bind DNA to the metal film.
"I was trying to develop a measurement technique to categorize biomolecules on a surface through breaking and reforming of the chemical bonds," Wong said. "Fixing DNA molecules on a solid substrate is pretty common. I guess nobody who made the same mistake I did happened to look under the microscope."
[. . .]
One of the most exciting findings in this study is that the patterns are not purely chemical, but are influenced by residual stress in the metal film. The research suggests that the metal's preexisting tension or compression determines the shapes that emerge. Thus, two processes, one chemical and one mechanical, worked together to yield the patterns.
This type of coupling, formed between catalysis-driven deformations of an interface and the underlying chemical reactions, is unusual in laboratory experiments but common in nature. Enzymes catalyze growth in nature, which deforms cells and tissue. It's this mechanical instability that makes tissue grow into particular shapes, some of which resemble the ones seen in Wong's experiments.
"In the biological world, this kind of coupling is actually ubiquitous," Zocchi said. "We just don't think of it in laboratory experiments because most laboratory experiments about pattern formation are done in liquids. That's what makes this discovery so exciting. It gives us a non-living laboratory system in which to study this kind of coupling and its incredible pattern-forming ability."
The study of pattern formation in chemical reactions began in 1951 when the Soviet chemist Boris Belousov accidentally discovered a chemical system that could spontaneously oscillate in time, which inaugurated the new fields of chemical pattern formation and nonequilibrium thermodynamics.
At the same time and independently, the British mathematician Alan Turing discovered that chemical systems, later termed "reaction-diffusion systems," could spontaneously form patterns in space, such as stripes or polka dots. The reaction-diffusion dynamics observed in Wong's experiments mirrored the theoretical ones posited by Turing.
Although the field of complex systems in physics and pattern formation enjoyed a time in the spotlight during the 1980s and 90s, to this day, the experimental systems used to study chemical pattern formation in the laboratory are essentially variants of ones introduced in the 1950s. The Wong-Zocchi system represents a major advance in the experimental study of chemical pattern formation.
[Link to full article. (https://phys.org/news/2025-03-serendipitous-discovery-reveals-stress-chemistry.html)]
The paper (https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.9.035201) is behind a paywall.
QuoteAbstract:
We present a solid state system which spontaneously generates remarkable engraving patterns on the surface of Ge. The layered construction, with a metal film on the Ge surface, results in coupling of the metal catalyzed etching reaction with the long range stress field at the Ge-metal interface.
The etching patterns generated have similarities with Turing patterns, hydrodynamic patterns, crack propagation, and biological form. We describe spirals, radial patterns, and more disordered structures. Euler buckling of the metal layer generates a characteristic wavelength for some patterns.