Researcher finds inspiration from spider webs and beetles to harvest fresh water from thin air

A team of researchers is designing novel systems to capture water vapour in the air and turn it into liquid.

University of Waterloo professor Michael Tam and his PhD students Yi Wang and Weinan Zhao have developed sponges or membranes with a large surface area that continually capture moisture from their surrounding environment.

Traditionally, fresh water for consumption is collected from rivers, lakes, groundwater, and oceans (with treatment). The current technologies Dr. Tam is developing are inspired by nature to harvest water from alternative sources as the world is facing a serious challenge with freshwater scarcity.

"A spider's web is an engineering marvel," said Tam, a University Research Chair in the field of functional colloids and sustainable nanomaterials. "Water is efficiently captured by the web. The spider doesn't need to go to the river to drink, as it traps moisture from the air."

Similarly, Namib desert beetles have no easy access to water but acquire water from thin air by leaning into the wind to capture droplets of water from the fog with their textured body armour. This allows the moisture to accumulate and drip into their mouths.

Tam and his research group are engaged in biomimetic surface engineering for sustainable water harvesting. One technology Tam is designing is called atmospheric water harvesting. To mimic the beetle's unique surface structure, Tam's research group is designing a similar surface structure using a cellulose-stabilized wax emulsion to fabricate surfaces that attract tiny water droplets while swiftly releasing larger ones.

Tam is working with net zero carbon materials, such as natural and plant-based materials, to develop sustainable technologies. His research group is developing technologies that capture and repel water droplets by harnessing the power of interfacial science and nanotechnology. He has successfully developed superhydrophobic and waterproof paper. He is also engineering a smart and tunable surface that captures water from the air and dehumidifies it with minimal energy consumption.

The next step is to develop a scalable process to engineer such surfaces.

Solar evaporation systems directly harvest solar energy, absorbing water and generating fresh collectible vapour through evaporation. Unique mushroom structures inspired the smart biomimetic structural designs for solar evaporation.

The proposed freshwater generation systems are inexpensive, energy-efficient, and environmentally friendly.

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New ice is like a snapshot of liquid water

A collaboration between scientists at Cambridge and UCL has led to the discovery of a new form of ice that more closely resembles liquid water than any other and may hold the key to understanding this most famous of liquids.

The new form of ice is amorphous. Unlike ordinary crystalline ice where the molecules arrange themselves in a regular pattern, in amorphous ice the molecules are in a disorganised form that resembles a liquid.

In this paper, published in Science, the team created a new form of amorphous ice in experiment and achieved an atomic-scale model of it in computer simulation. The experiments used a technique called ball-milling, which grinds crystalline ice into small particles using metal balls in a steel jar. Ball-milling is regularly used to make amorphous materials, but it had never been applied to ice.

The team found that ball-milling created a novel amorphous form of ice, which unlike all other known ices, had a density similar to that of liquid water and whose state resembled water in solid form. They named the new ice medium-density amorphous ice (MDA).

To understand the process at the molecular scale the team employed computational simulation. By mimicking the ball-milling procedure via repeated random shearing of crystalline ice, the team successfully created a computational model of MDA.

"Our discovery of MDA raises many questions on the very nature of liquid water and so understanding MDA's precise atomic structure is very important" comments co-author Dr. Michael Davies, who carried out the computational modelling. "We found remarkable similarities between MDA and liquid water."

A happy medium

Amorphous ices have been suggested to be models for liquid water. Until now, there have been two main types of amorphous ice: high-density and low-density amorphous ice.

As the names suggest, there is a large density gap between them. This density gap, combined with the fact that the density of liquid water lies in the middle, has been a cornerstone of our understanding of liquid water. It has led in part to the suggestion that water consists of two liquids: one high- and one low-density liquid.

Senior author Professor Christoph Salzmann said: "The accepted wisdom has been that no ice exists within that density gap. Our study shows that the density of MDA is precisely within this density gap and this finding may have far-reaching consequences for our understanding of liquid water and its many anomalies."

A high-energy geophysical material

The discovery of MDA gives rise to the question: where might it exist in nature? Shear forces were discovered to be key to creating MDA in this study. The team suggests ordinary ice could undergo similar shear forces in the ice moons due to the tidal forces exerted by gas giants such as Jupiter.

Moreover, MDA displays one remarkable property that is not found in other forms of ice. Using calorimetry, they found that when MDA recrystallises to ordinary ice it releases an extraordinary amount of heat. The heat released from the recrystallization of MDA could play a role in activating tectonic motions. More broadly, this discovery shows water can be a high-energy geophysical material.

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The bubbling universe: A previously unknown phase transition in the early universe

Think of bringing a pot of water to the boil: As the temperature reaches the boiling point, bubbles form in the water, burst and evaporate as the water boils. This continues until there is no more water changing phase from liquid to steam.

This is roughly the idea of what happened in the very early universe, right after the Big Bang, 13.7 billion years ago.

The idea comes from particle physicists Martin S. Sloth from the Center for Cosmology and Particle Physics Phenomenology at University of Southern Denmark and Florian Niedermann from the Nordic Institute for Theoretical Physics (NORDITA) in Stockholm. Niedermann is a previous postdoc in Sloth's research group. In this new scientific article, they present an even stronger basis for their idea.

Many bubbles crashing into each other

"One must imagine that bubbles arose in various places in the early universe. They got bigger and they started crashing into each other. In the end, there was a complicated state of colliding bubbles, which released energy and eventually evaporated," said Martin S. Sloth.

The background for their theory of phase changes in a bubbling universe is a highly interesting problem with calculating the so-called Hubble constant; a value for how fast the universe is expanding. Sloth and Niedermann believe that the bubbling universe plays a role here.

The Hubble constant can be calculated very reliably by, for example, analyzing cosmic background radiation or by measuring how fast a galaxy or an exploding star is moving away from us. According to Sloth and Niedermann, both methods are not only reliable, but also scientifically recognized. The problem is that the two methods do not lead to the same Hubble constant. Physicists call this problem "the Hubble tension."

Is there something wrong with our picture of the early universe?

"In science, you have to be able to reach the same result by using different methods, so here we have a problem. Why don't we get the same result when we are so confident about both methods?" said Florian Niedermann.

Sloth and Niedermann believe they have found a way to get the same Hubble constant, regardless of which method is used. The path starts with a phase transition and a bubbling universe -- and thus an early, bubbling universe is connected to "the Hubble tension."

"If we assume that these methods are reliable -- and we think they are -- then maybe the methods are not the problem. Maybe we need to look at the starting point, the basis, that we apply the methods to. Maybe this basis is wrong."

An unknown dark energy

The basis for the methods is the so-called Standard Model, which assumes that there was a lot of radiation and matter, both normal and dark, in the early universe, and that these were the dominant forms of energy. The radiation and the normal matter were compressed in a dark, hot and dense plasma; the state of the universe in the first 380,000 years after Big Bang.

When you base your calculations on the Standard Model, you arrive at different results for how fast the universe is expanding -- and thus different Hubble constants.

But maybe a new form of dark energy was at play in the early universe? Sloth and Niedermann think so.

If you introduce the idea that a new form of dark energy in the early universe suddenly began to bubble and undergo a phase transition, the calculations agree. In their model, Sloth and Niedermann arrive at the same Hubble constant when using both measurement methods. They call this idea New Early Dark Energy -- NEDE.

Change from one phase to another -- like water to steam

Sloth and Niedermann believe that this new, dark energy underwent a phase transition when the universe expanded, shortly before it changed from the dense and hot plasma state to the universe we know today.

- This means that the dark energy in the early universe underwent a phase transition, just as water can change phase between frozen, liquid and steam. In the process, the energy bubbles eventually collided with other bubbles and along the way released energy, said Niedermann.

"It could have lasted anything from an insanely short time -- perhaps just the time it takes two particles to collide -- to 300,000 years. We don't know, but that is something we are working to find out," added Sloth.

Do we need new physics?

So, the phase transition model is based on the fact that the universe does not behave as the Standard Model tells us. It may sound a little scientifically crazy to suggest that something is wrong with our fundamental understanding of the universe; that you can just propose the existence of hitherto unknown forces or particles to solve the Hubble tension.

"But if we trust the observations and calculations, we must accept that our current model of the universe cannot explain the data, and then we must improve the model. Not by discarding it and its success so far, but by elaborating on it and making it more detailed so that it can explain the new and better data," said Martin S. Sloth, adding:

"It appears that a phase transition in the dark energy is the missing element in the current Standard Model to explain the differing measurements of the universe's expansion rate.

How fast is the universe expanding?

The Hubble constant is a value for how fast the universe is expanding.

In Martin S. Sloth and Florian Niedermann's model, the Hubble constant is 72. Approximately. After all, large distances are being calculated, so we must allow for uncertainty of a few decimals.

What does 72 mean? It means 72 km per second per Megaparsec. Megaparsecs are a measure of the distance between, for example, two galaxies, and one megaparsec is 30,000,000,000,000,000,000 km. For every megaparsec between us and, for example, a galaxy, the galaxy moves away from us at 72 km per second.

When you measure the distance to galaxies by supernovas, you get a Hubble constant of approx. 73 (km/s)/megaparsec. But when measuring on the first light particles (the cosmic background radiation), the Hubble constant is 67.4 (km/s)/megaparsec.

Read more at Science Daily

Botany: From the soil to the sky

Every day, about one quadrillion gallons of water are silently pumped from the ground to the treetops. Earth's plant life accomplishes this staggering feat using only sunlight. It takes energy to lift all this liquid, but just how much was an open question until this year.

Researchers at UC Santa Barbara have calculated the tremendous amount of power used by plants to move water through their xylem from the soil to their leaves. They found that, on average, it was an additional 14% of the energy the plants harvested through photosynthesis. On a global scale, this is comparable to the production of all of humanity's hydropower. Their study, published in the Journal of Geophysical Research: Biogeosciences, is the first to estimate how much energy goes into lifting water up to plant canopies, both for individual plants and worldwide.

"It takes power to move water up through the xylem of the tree. It takes energy. We're quantifying how much energy that is," said first author Gregory Quetin, a postdoctoral researcher in the Department of Geography. This energy is in addition to what a plant produces via photosynthesis. "It's energy that's being harvested passively from the environment, just through the tree's structure."

Photosynthesis requires carbon dioxide, light and water. CO2 is widely available in the air, but the other two ingredients pose a challenge: Light comes from above, and water from below. So, plants need to bring the water up (sometimes a considerable distance) to where the light is.

More complex plants accomplish this with a vascular system, in which tubes called xylem bring water from the roots to the leaves, while other tubes called phloem move sugar produced in the leaves down to the rest of the plant. "Vascular plants evolving xylem is a huge deal that allowed for trees to exist," Quetin said.

Many animals also have a vascular system. We evolved a closed circulatory system with a heart that pumps blood through arteries, capillaries and veins to deliver oxygen and nutrients around our bodies. "This is a function that many organisms pay a lot for," said co-author Anna Trugman, an assistant professor in the Department of Geography. "We pay for it because we have to keep our hearts beating, and that's probably a lot of our metabolic energy."

Plants could have evolved hearts, too. But they didn't. And it saves them a lot of metabolic energy.

In contrast to animals, plant circulatory systems are open and powered passively. Sunlight evaporates water, which escapes from pores in the leaves. This creates a negative pressure that pulls up the water beneath it. Scientists call this process "transpiration."

In essence, transpiration is merely another way that plants harvest energy from sunlight. It's just that, unlike in photosynthesis, this energy doesn't need to be processed before it can be put to use.

Scientists understand this process fairly well, but no one had ever estimated how much energy it consumes. "I've only seen it mentioned specifically as energy in one paper," co-author Leander Anderegg said, "and it was to say that 'this is a really large number. If plants had to pay for it with their metabolism, they wouldn't work.'"

This particular study grew out of basic curiosity. "When Greg [Quetin]and I were both graduate students, we were reading a lot about plant transpiration," recalled Anderegg, now an assistant professor in the Department of Ecology, Evolution, and Marine Biology. "At some point Greg asked, 'How much work do plants do just lifting water against gravity?'

"I said, 'I have no idea. I wonder if anyone knows?' And Greg said, 'surely we can calculate that.'"

About a decade later, they circled back and did just that. The team combined a global database of plant conductance with mathematical models of sap ascent to estimate how much power the world's plant life devotes to pumping water. They found that the Earth's forests consume around 9.4 petawatt-hours per year. That's on par with global hydropower production, they quickly point out.

This is about 14.2% of the energy that plants take in through photosynthesis. So it's a significant chunk of energy that plants benefit from but don't have to actively process. This free energy passes to the animals and fungi that consume plants, and the animals that consume them, and so on.

Surprisingly, the researchers discovered that fighting gravity accounts for only a tiny fraction of this total. Most of the energy goes into simply overcoming the resistance of a plant's own stem.

These findings may not have many immediate applications, but they help us better understand life on Earth. "The fact that there's a global energy stream of this magnitude that we didn't have quantified, is mildly jarring," Quetin said. "It does seem like a concept that slipped through the cracks."

The energies involved in transpiration seem to fall in between the scales that different scientists examine. It's too big for plant physiologists to consider and too small for scientists who study Earth systems to bother with, so it was forgotten. And it's only within the past decade that scientists have collected enough data on water use and xylem resistance to begin addressing the energy of transpiration at global scales, the authors explained.

Within that time, scientists have been able to refine the significance of transpiration in Earth systems using new observations and models. It affects temperatures, air currents and rainfall, and helps shape a region's ecology and biodiversity. Sap ascent power is a small component of transpiration overall, but the authors suspect it may turn out to be noteworthy given the significant energy involved.

It's still early days, and the team admits there's a lot of work to do in tightening their estimates. Plants vary widely in how conductive their stems are to water flow. Compare a hardy desert juniper with a riverside cottonwood, for instance. "A juniper tree that is very drought adapted has a very high resistance," Anderegg said, "while cottonwoods just live to pump water."

Read more at Science Daily

Liquid water beneath Martian south polar cap?

A Southwest Research Institute scientist measured the properties of ice-brine mixtures as cold as -145 degrees Fahrenheit to help confirm that salty water likely exists between grains of ice or sediment under the ice cap at Mars' south pole. Laboratory measurements conducted by SwRI geophysicist Dr. David Stillman support oddly bright reflections detected by the MARSIS subsurface sounding radar aboard ESA's Mars Express orbiter.

With a 130-foot antenna, MARSIS flies over the planet, bouncing radio waves over a selected area and then receiving and analyzing the echoes or reflections. Any near-surface liquid water should send a strong bright signal, whereas the radar signal for ice and rock would be much smaller.

Because conventional models assume the Mars south polar cap experiences temperatures much lower than the melting point of water, many scientists have questioned the presence of liquid water. Clay, hydrated salts and saline ices have been proposed as potential explanations for the source of the bright basal reflections. The Italian-led team investigating the proposed phenomena used previously published data, simulations and new laboratory measurements.

"Lakes of liquid water actually exist beneath glaciers in Arctic and Antarctic regions, so we have Earth analogs for finding liquid water below ice," said Stillman, a specialist in detecting water in any format -- liquid, ice or absorbed -- on planetary bodies and co-author of a paper describing these findings. "The exotic salts that we know exist on Mars have amazing 'antifreeze' properties allowing brines to remain liquid down to -103 degrees Fahrenheit. We studied these salts in our lab to understand how they would respond to radar."

Stillman has over a decade of experience measuring the properties of materials at cold temperatures to detect and characterize subsurface ice, unfrozen water and the potential for life throughout the solar system. For this project, Stillman measured the properties of perchlorate brines in an SwRI environmental chamber that produces near-liquid-nitrogen temperatures at Mars-like pressures.

"My Italian colleagues reached out to see if my laboratory experiment data would support the presence of liquid water beneath the Martian ice cap," Stillman said. "The research showed that we don't have to have lakes of perchlorate and chloride brines, but that these brines could exist between the grains of ice or sediments and are enough to exhibit a strong dielectric response. This is similar to how seawater saturates grains of sand at the shoreline or how flavoring permeates a slushie, but at -103 degrees Fahrenheit below a mile of ice near the South Pole of Mars."

Read more at Science Daily

Researchers film human viruses in liquid droplets at near-atomic detail

A pond in summer can reveal more about a fish than a pond in winter. The fish living in icy conditions might remain still enough to study its scales, but to understand how the fish swims and behaves, it needs to freely move in three dimensions. The same holds true for analyzing how biological items, such as viruses, move in the human body, according to a research team led by Deb Kelly, Huck Chair in Molecular Biophysics and professor of biomedical engineering at Penn State, who has used advanced electron microscopy (EM) technology to see how human viruses move in high resolution in a near-native environment. The visualization technique could lead to improved understanding of how vaccine candidates and treatments behave and function as they interact with target cells, Kelly said.

In an effort to expand the tools scientists have to study the microscopic world, researchers recorded live, 20-second-long movies of human viruses floating in liquid at near-atomic detail in an electron microscope. The same degree of information, immediately available as they record, may take up to 24 hours to acquire using traditional static imaging methods. Their approach and results were made available online July 24 in Advanced Materials.

"The challenge remained to view biological materials in dynamic systems that reflects their authentic performance in the body," said Kelly, who also directs the Penn State Center for Structural Oncology. "Our results show new structures and active insights of human viruses contained in minute volumes of liquid -- the same size as respiratory droplets that spread SARS-CoV-2."

Cryogenic electron microscopy (cryo-EM) is becoming the field's gold standard for observing samples at or beyond atomic resolution, according to Kelly. The technique involves flash freezing the sample and focusing a beam of electrons through it. The electrons and the sample's components interact, which is captured by detectors embedded in the instrument. Thousands of images can be processed to calculate what the item looks like in 3D -- but more is needed to fully understand how the item functions in a more natural setting.

"While cryo-EM can tell us a lot of information, it still produces a static image," said GM Jonaid, the paper's first author and a student in the Bioinformatics and Genomics Graduate Program in the Huck Institutes of the Life Sciences. Jonaid is conducting his doctoral dissertation research in Kelly's lab. "With improved chips and a powerful direct detector on the microscope, we can accumulate a lot of movie frames to view how the sample acts in real time. We can see things how they exist -- not just how we prepared them."

The researchers used adeno-associated virus (AAV) as a model system to demonstrate their approach. AAV is a biological nanoparticle that can be used to help deliver vaccines or treatments directly to cells. The platform is based on a hijacked adenovirus, which can easily enter several kinds of cells. The ease with which it interacts with cells makes it a useful capsule to transport its engineered payload.

"AAV is a well-known, gene therapy vehicle with current applications involved in drug delivery and vaccine development for COVID-19," Kelly said. "This model system is already well-studied so we can use it to validate our approach with the goal of seeing biological entitles in a liquid state, as maintained in the human body."

The researchers applied minute volumes of liquid solution containing AAV to the wells of specialized silicon nitride microchips, commercially supplied by Protochips Inc. They then placed the microchip assemblies in the EM to examine the viruses in action.

"The images are very comparable to cryo-EM data, but the preparation was less complex, less technically involved," Jonaid said. "Once we had the images, taken rapidly, like frames of a movie, we processed them just like we would any other high-resolution data."

The results were videos of AAV moving in liquid, with subtle changes in the particle's surface, suggesting that the particle's physical properties change as it explores its environment, Kelly said. The resolution was close to three to four Angstroms (a single atom is measured as one Angstrom).

Once they proved the imaging strategies worked, the researchers set their sights on a smaller target: antibodies produced by COVID-19 patients.

"We saw how antibodies contained in the serum of COVID-19 patients interacted with the remaining SARS-CoV-2 particles," Kelly said, noting that the ability to observe such interactions would be especially useful when assessing the viability of vaccine candidates prior to clinical trials.

Kelly and her team plan to continue investigating the molecular underpinnings of SARS-CoV-2 and host-receptor proteins using liquid phase-EM, as a complement to the information garnered from cryo-EM results.

"You really need data from both techniques to understand how viruses look and behave in the living body," Kelly said. "Visualizing the dynamic movement in solution complements high-resolution snapshots to reveal more complete information."

Read more at Science Daily

Preconditions for life present 3.5 billion years ago

Microbial life already had the necessary conditions to exist on our planet 3.5 billion years ago. This was the conclusion reached by a research team after studying microscopic fluid inclusions in barium sulfate (barite) from the Dresser Mine in Marble Bar, Australia. In their publication "Ingredients for microbial life preserved in 3.5-billion-year-old fluid inclusions," the researchers suggest that organic carbon compounds which could serve as nutrients for microbial life already existed at this time. The study by first author Helge Mißbach (University of Göttingen, Germany) was published in the journal Nature Communications. Co-author Volker Lüders from the GFZ German Research Center for Geosciences carried out carbon isotope analyses on gases in fluid inclusions.

Fluid inclusions show potential for prehistoric life

Lüders assesses the results as surprising, although he cautions against misinterpreting them. "One should not take the study results as direct evidence for early life," says the GFZ researcher. Rather, the findings on the 3.5-billion-year-old fluids showed the existence of the potential for just such prehistoric life. Whether life actually arose from it at that time cannot be determined. Based on the results, "we now know a point in time from which we can say it would have been possible," explains Lüders.

Australian barites as geo-archives

Fluid inclusions in minerals are microscopic geo-archives for the migration of hot solutions and gases in the Earth's crust. Primary fluid inclusions were formed directly during mineral growth and provide important information about the conditions under which they were formed. This includes the pressure, temperature and the solution composition. In addition to an aqueous phase, fluid inclusions can also contain gases whose chemistry can persist for billions of years. The fluid inclusions examined in this study were trapped during crystallization of the host minerals. The fluid inclusions investigated in this study originate from the Dresser Mine in Australia. They were trapped during crystallisation of the host minerals of barium sulphate (barite). The research team analysed them extensively for their formation conditions, biosignatures and carbon isotopes.

In the course of the analyses, it turned out that they contained primordial metabolism -- and thus energy sources for life. The results of Lüders' carbon isotope analysis provided additional evidence for different carbon sources. While the gas-rich inclusions of gray barites contained traces of magmatic carbon, clear evidence of an organic origin of the carbon could be found in the fluid inclusions of black barites.

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Scientists create liquid crystals that look a lot like their solid counterparts

 A team at the University of Colorado Boulder has designed new kinds of liquid crystals that mirror the complex structures of some solid crystals -- a major step forward in building flowing materials that can match the colorful diversity of forms seen in minerals and gems, from lazulite to topaz.

The group's findings, published today in the journal Nature, may one day lead to new types of smart windows and television or computer displays that can bend and control light like never before.

The results come down to a property of solid crystals that will be familiar to many chemists and gemologists: Symmetry.

Ivan Smalyukh, a professor in the Department of Physics at CU Boulder, explained that scientists categorize all known crystals into seven main classes, plus many more sub-classes -- in part based on the "symmetry operations" of their internal atoms. In other words, how many ways can you stick an imaginary mirror inside of a crystal or rotate it and still see the same structure? Think of this classification system as Baskin-Robbins' 32 flavors but for minerals.

To date, however, scientists haven't been able to create liquid crystals -- flowing materials that are found in most modern display technologies -- that come in those same many flavors.

"We know everything about all the possible symmetries of solid crystals that we can make. There are 230 of them," said Smalyukh, senior author of the new study who is also a fellow of the Renewable and Sustainable Energy Institute (RASEI) at CU Boulder. "When it comes to nematic liquid crystals, the kind in most displays, we only have a few that have been demonstrated so far."

That is, until now.

In their latest findings, Smalyukh and his colleagues came up with a way to design the first liquid crystals that resemble monoclinic and orthorhombic crystals -- two of those seven main classes of solid crystals. The findings, he said, bring a bit more of order to the chaotic world of fluids.

"There are a lot of possible types of liquid crystals, but, so far, very few have been discovered," Smalyukh said. "That is great news for students because there's a lot more to find."

Symmetry in action

To understand symmetry in crystals, first picture your body. If you place a giant mirror running down the middle of your face, you'll see a reflection that looks (more or less) like the same person.

Solid crystals have similar properties. Cubic crystals, which include diamonds and pyrite, for example, are made up of atoms arranged in the shape of a perfect cube. They have a lot of symmetry operations.

"If you rotate those crystals by 90 or 180 degrees around many special axes, for example, all of the atoms stay in the right places," Smalyukh said.

But there are other types of crystals, too. The atoms inside monoclinic crystals, which include gypsum or lazulite, are arranged in a shape that looks like a slanted column. Flip or rotate these crystals all you want, and they still have only two distinct symmetries -- one mirror plane and one axis of 180-degree rotation, or the symmetry that you can see by spinning a crystal around an axis and noticing that it looks the same every 180 degrees. Scientists call that a "low-symmetry" state.

Traditional liquid crystals, however, don't display those kinds of complex structures. The most common liquid crystals, for example, are made up of tiny rod-shaped molecules. Under the microscope, they tend to line up like dry pasta noodles tossed into a pot, Smalyukh said.

"When things can flow they don't usually exhibit such low symmetries," Smalyukh said.

Order in liquids

He and his colleagues wanted to see if they could change that. To begin, the team mixed together two different kinds of liquid crystals. The first was the common class made up of rod-shaped molecules. The second was made up of particles shaped like ultra-thin disks.

When the researchers brought them together, they noticed something strange: Under the right conditions in the lab, those two types of crystals pushed and squeezed each other, changing their orientation and arrangement. The end result was a nematic liquid crystal fluid with symmetry that looks a lot like that of a solid monoclinic crystal. The molecules inside displayed some symmetry, but only one mirror plane and one axis of 180-degree rotation.

The group had created, in other words, a material with the mathematical properties of a lazulite or gypsum crystal -- but theirs could flow like a fluid.

"We're asking a very fundamental question: What are the ways that you can combine order and fluidity in a single material?" Smalyukh said.

And, the team's creations are dynamic: If you heat the liquid crystals up or cool them down, for example, you can morph them into a rainbow of different structures, each with their own properties, said Haridas Mundoor, lead author of the new paper. That's pretty handy for engineers.

"This offers different avenues that can modify display technologies, which may enhance the energy efficiency in performance of devices like smart phones," said Mundoor, a postdoctoral research associate at CU Boulder.

He and his colleagues are still nowhere near making liquid crystals that can replicate the full spectrum of solid crystals. But the new paper gets them closer than ever before -- good news for fans of shiny things everywhere.

Read more at Science Daily

Liquid water at 170 degrees Celsius

 Using the X-ray laser European XFEL, a research team has investigated how water heats up under extreme conditions. In the process, the scientists were able to observe water that remained liquid even at temperatures of more than 170 degrees Celsius. The investigation revealed an anomalous dynamic behaviour of water under these conditions. The results of the study, which are published in the Proceedings of the National Academy of Sciences (PNAS), are of fundamental importance for the planning and analysis of investigations of sensitive samples using X-ray lasers.

European XFEL, an international research facility, which extends from the DESY site in Hamburg to the neighbouring town of Schenefeld in Schleswig-Holstein, is home to the most powerful X-ray laser in the world. It can generate up to 27,000 intense X-ray flashes per second. For their experiments, the researchers used series of 120 flashes each. The individual flashes were less than a millionth of a second apart (exactly 0.886 microseconds). The scientists sent these pulse trains into a thin, water-filled quartz glass tube and observed the reaction of the water.

"We asked ourselves how long and how strongly water can be heated in the X-ray laser and whether it still behaves like water," explains lead author Felix Lehmkühler from DESY. "For example, does it still function as a coolant at high temperatures?" A detailed understanding of superheated water is also essential for a large number of investigations on heat-sensitive samples, such as polymers or biological samples.

"With the X-ray flashes, we were able to heat the water up to 172 degrees Celsius within a ten thousandth of a second without it evaporating," reports Lehmkühler. Such a boiling delay can normally only be observed up to about 110 degrees Celsius. "But that is not the only anomalous feature," the physicist emphasises. The scientists investigated the movement of silicon nanospheres floating in the water as markers for the dynamics in the sample. "In the extremely overheated water, we observed that the movement of silicon dioxide nanospheres deviated significantly from the expected random Brownian molecular movement. This indicates an uneven heating of the sample," says Lehmkühler. Existing theoretical models cannot yet satisfactorily explain this behaviour because they are not designed for water under these extreme conditions.

Thanks to the rapid flash sequence of the European XFEL, the researchers were able to observe the process in extreme detail. "What makes the European XFEL unique is the high repetition rate, that is, the high number of pulses per second," explains co-author Adrian Mancuso, head of the SPB/SFX instrument at the European XFEL where the experiments took place. "And we have all the instrumentation in place -- such as fast cameras, diagnostics and more -- to make these experiments possible." For instance, the Adaptive Gain Integrating Pixel Detector (AGIPD) developed by a DESY-led consortium can take around 350 serial images at intervals of only 220 billionths of a second (nanoseconds).

This setup not only allowed the superheated water to be generated, but also enabled the scientists to carry out precisely controlled series of experiments with X-ray flashes of reduced intensity. "Using silicon filters, we fine-tuned the energy of the pulses so that we were able to control exactly how much the water was heated," reports Lehmkühler. "For example, we were able to determine how strong the X-ray flashes should be so that the temperature of an aqueous sample remains more or less constant."

This enables researchers to better plan experiments with heat-sensitive samples at the X-ray laser, for example. On the other hand, the heating effect can also be used in a targeted manner if its exact course is known. The team plans to further investigate these effects also within the framework of the Centre for Molecular Water Science (CMWS), which is currently being set up at DESY.

Read more at Science Daily

After a century of searching, scientists find new liquid phase

Researchers at the University of Colorado Boulder's Soft Materials Research Center (SMRC) have discovered an elusive phase of matter, first proposed more than 100 years ago and sought after ever since.

The team describes the discovery of what scientists call a "ferroelectric nematic" phase of liquid crystal in a study published today in the Proceedings of the National Academy of Sciences. The discovery opens a door to a new universe of materials, said co-author Matt Glaser, a professor in the Department of Physics.

Nematic liquid crystals have been a hot topic in materials research since the 1970s. These materials exhibit a curious mix of fluid- and solid-like behaviors, which allow them to control light. Engineers have used them extensively to make the liquid crystal displays (LCDs) in many laptops, TVs and cellphones.

Think of nematic liquid crystals like dropping a handful of pins on a table. The pins in this case are rod-shaped molecules that are "polar" -- with heads (the blunt ends) that carry a positive charge and tails (the pointy ends) that are negatively charged. In a traditional nematic liquid crystal, half of the pins point left and the other half point right, with the direction chosen at random.

A ferroelectric nematic liquid crystal phase, however, is much more disciplined. In such a liquid crystal, patches or "domains" form in the sample in which the molecules all point in the same direction, either right or left. In physics parlance, these materials have polar ordering.

Noel Clark, a professor of physics and director of the SMRC, said that his team's discovery of one such liquid crystal could open up a wealth of technological innovations -- from new types of display screens to reimagined computer memory.

"There are 40,000 research papers on nematics, and in almost any one of them you see interesting new possibilities if the nematic had been ferroelectric," Clark said.

Under the microscope

The discovery is years in the making.

Nobel Laureates Peter Debye and Max Born first suggested in the 1910s that, if you designed a liquid crystal correctly, its molecules could spontaneously fall into a polar ordered state. Not long after that, researchers began to discover solid crystals that did something similar: Their molecules pointed in uniform directions. They could also be reversed, flipping from right to left or vice versa under an applied electric field. These solid crystals were called "ferroelectrics" because of their similarities to magnets. (Ferrum is Latin for "iron").

In the decades since, however, scientists struggled to find a liquid crystal phase that behaved in the same way. That is, until Clark and his colleagues began examining RM734, an organic molecule created by a group of British scientists several years ago.

That same British group, plus a second team of Slovenian scientists, reported that RM734 exhibited a conventional nematic liquid crystal phase at higher temperatures. At lower temperatures, another unusual phase appeared.

When Clark's team tried to observe that strange phase under the microscope they noticed something new. Under a weak electric field, a palette of striking colors developed toward the edges of the cell containing the liquid crystal.

"It was like connecting a light bulb to voltage to test it but finding the socket and hookup wires glowing much more brightly instead," Clark said.

Stunning results

So, what was happening?

The researchers ran more tests and discovered that this phase of RM734 was 100 to 1,000 times more responsive to electric fields than the usual nematic liquid crystals. This suggested that the molecules that make up the liquid crystal demonstrated strong polar order.

"When the molecules are all pointing to the left, and they all see a field that says, 'go right,' the response is dramatic," Clark said.

The team also discovered that distinct domains seemed to form spontaneously in the liquid crystal when it cooled from higher temperature. There were, in other words, patches within their sample in which the molecules seemed to be aligned.

"That confirmed that this phase was, indeed, a ferroelectric nematic fluid," Clark said.

That alignment was also more uniform than the team was expecting.

"Entropy reigns in a fluid," said Joe MacLennan, a study coauthor and a professor of physics at CU Boulder. "Everything is wiggling around, so we expected a lot of disorder."

When the researchers examined how well aligned the molecules were inside a single domain, "we were stunned by the result," MacLennan said. The molecules were nearly all pointing in the same direction.

The team's next goal is to discover how RM734 achieves this rare feat. Glaser and SMRC researcher Dmitry Bedrov of the University of Utah, are currently using computer simulation to tackle this question.

"This work suggests that there are other ferroelectric fluids hiding in plain sight," Clark said. "It is exciting that right now techniques like artificial intelligence are emerging that will enable an efficient search for them."

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A new way to measure how water moves

When a chemical spills in the environment, it's important to know how quickly the spill will spread. If a farmer irrigates a crop, the person will need to know how fast the water should move through the soil and be absorbed by the roots. In both cases, a good understanding of water pore structure is necessary.

A new method to measure pore structure and water flow is described in a study published in the journal Water Resources Research. With it, scientists should be able to more accurately determine how fast water, contaminants, nutrients and other liquids move through the soil -- and where they go.

The mathematical model was validated by researchers at the University of California, Davis, California State University, Northridge and University of North Carolina at Chapel Hill.

"This will open a whole new direction that will help us use our resources more efficiently and better understand the flow of water, contaminants and nutrients," said corresponding author and UC Davis assistant professor Majdi Abou Najm, who developed the model when he was at the American University of Beirut.

NOT ONE-SIZE-FITS ALL

One of the most important equations in hydrology, Darcy's law, has long been used to describe the flow of fluids through a porous medium, like rocks and soil. But that equation assumes a one-size-fits all estimation of pore size, when the reality is more complicated.

"Our model finds a middle ground between reality, which has an infinite number of pore sizes, and the current model, which represents them with one average pore size," said Abou Najm.

CHEAP AND ACCESSIBLE

The new model, which was tested on four sands for the study, has the added benefit of being relatively cheap and accessible to use in a variety of environments. The study said that most pore size measurement methods require collecting samples of limited size for lab analysis. This new method provides a simple, inexpensive approach to measuring a variety of pore sizes directly in the field using items that can be bought in a typical grocery store, such as soup thickeners or food additives.

From Science Daily

Big Bang query: Mapping how a mysterious liquid became all matter

The leading theory about how the universe began is the Big Bang, which says that 14 billion years ago the universe existed as a singularity, a one-dimensional point, with a vast array of fundamental particles contained within it. Extremely high heat and energy caused it to inflate and then expand into the cosmos as we know it -- and, the expansion continues to this day.

The initial result of the Big Bang was an intensely hot and energetic liquid that existed for mere microseconds that was around 10 billion degrees Fahrenheit (5.5 billion Celsius). This liquid contained nothing less than the building blocks of all matter. As the universe cooled, the particles decayed or combined giving rise to...well, everything.

Quark-gluon plasma (QGP) is the name for this mysterious substance so called because it was made up of quarks -- the fundamental particles -- and gluons, which physicist Rosi J. Reed describes as "what quarks use to talk to each other."

Scientists like Reed, an assistant professor in Lehigh University's Department of Physics whose research includes experimental high-energy physics, cannot go back in time to study how the Universe began. So they re-create the circumstances, by colliding heavy ions, such as Gold, at nearly the speed of light, generating an environment that is 100,000 times hotter than the interior of the sun. The collision mimics how quark-gluon plasma became matter after the Big Bang, but in reverse: the heat melts the ions' protons and neutrons, releasing the quarks and gluons hidden inside them.

There are currently only two operational accelerators in the world capable of colliding heavy ions -- and only one in the U.S.: Brookhaven National Lab's Relativistic Heavy Ion Collider (RHIC). It is about a three-hour drive from Lehigh, in Long Island, New York.

Reed is part of the STAR Collaboration , an international group of scientists and engineers running experiments on the Solenoidal Tracker at RHIC (STAR). The STAR detector is massive and is actually made up of many detectors. It is as large as a house and weighs 1,200 tons. STAR's specialty is tracking the thousands of particles produced by each ion collision at RHIC in search of the signatures of quark-gluon plasma.

"When running experiments there are two 'knobs' we can change: the species -- such as gold on gold or proton on proton -- and the collision energy," says Reed. "We can accelerate the ions differently to achieve different energy-to-mass ratio."

Using the various STAR detectors, the team collides ions at different collision energies. The goal is to map quark-gluon plasma's phase diagram, or the different points of transition as the material changes under varying pressure and temperature conditions. Mapping quark-gluon plasma's phase diagram is also mapping the nuclear strong force, otherwise known as Quantum Chromodynamics (QCD), which is the force that holds positively charged protons together.

"There are a bunch of protons and neutrons in the center of an ion," explains Reed. "These are positively charged and should repel, but there's a 'strong force' that keeps them together --  strong enough to overcome their tendency to come apart."

Understanding quark-gluon plasma's phase diagram, and the location and existence of the phase transition between the plasma and normal matter is of fundamental importance, says Reed.

"It's a unique opportunity to learn how one of the four fundamental forces of nature operates at temperature and energy densities similar to those that existed only microseconds after the Big Bang," says Reed.

Upgrading the RHIC detectors to better map the "strong force"

The STAR team uses a Beam Energy Scan (BES) to do the phase transition mapping. During the first part of the project, known as BES-I, the team collected observable evidence with "intriguing results." Reed presented these results at the 5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan in Hawaii in October 2018 in a talk titled: "Testing the quark-gluon plasma limits with energy and species scans at RHIC."

However, limited statistics, acceptance, and poor event plane resolution did not allow firm conclusions for a discovery. The second phase of the project, known as BES-II, is going forward and includes an improvement that Reed is working on with STAR team members: an upgrade of the Event Plan Detector. Collaborators include scientists at Brookhaven as well as at Ohio State University.

The STAR team plans to continue to run experiments and collect data in 2019 and 2020, using the new Event Plan Detector. According to Reed, the new detector is designed to precisely locate where the collision happens and will help characterize the collision, specifically how "head on" it is.

"It will also help improve the measurement capabilities of all the other detectors," says Reed.

The STAR collaboration expects to run their next experiments at RHIC in March 2019.

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Floating droplets: How droplets can 'levitate' on liquid surfaces

Visualization of vortices in a drop of silicone oil sitting on a warm bath. The temperature difference generates a recirculating flow that is visualized by shining a green laser light on fluorescent particles that are added as passive tracers within the drop.

A drop or two of cold cream in hot coffee can go a long way toward improving one's morning. But what if the two liquids didn't mix?

MIT scientists have now explained why under certain conditions a droplet of liquid should not coalesce with the liquid surface below. If the droplet is very cold, and the bath sufficiently hot, then the droplet should "levitate" on the bath's surface, as a result of the flows induced by the temperature difference.

The team's results, published today in the Journal of Fluid Mechanics, offer a detailed, mathematical understanding of drop coalescence, which can be observed in everday phenomena, from milk poured in coffee to raindrops skittering across puddles, and sprays created in surf zones.

The results may help researchers understand how biological or chemical substances are spread by rain or other sprays in nature. They could also serve as a guide for droplet-based designs, such as in microfluidic chips, in which droplets carrying various reagents can be designed to mix only in certain locations in a chip, at certain temperatures. With this new understanding, researchers could also engineer droplets to act as mechanical ball bearings in zero-gravity environments.

"Based on our new theory, engineers can determine what is the initial critical temperature difference they need to maintain two drops separately, and what is the maximum weight that a bearing constructed from these levitating drops would be able to sustain," says Michela Geri, a graduate student in MIT's Department of Mechanical Engineering and the study's lead author. "If you have a fundamental understanding, you can start designing things the way you want them to work."

Geri's co-authors are Bavand Keshavarz, a lecturer in mechanical engineering, John Bush, professor of applied mathematics in MIT's Department of Mathematics, and Gareth McKinley, the School of Engineering Professor of Teaching Innovation.

An uplifting experiment

The team's results grew out of a question that Bush posed in his graduate course 18.357 (Interfacial Phenomena): Why should a temperature difference play a role in a droplet's coalescence, or mixing?

Geri, who was taking the course at the time, took on the challenge, first by carrying out a series of experiments in McKinley's lab.

She built a small box, about the size of an espresso cup, with acrylic walls and a metal floor, which she placed on a hot/cold plate. She filled the cube with a bath of silicone oil, and just above the surface of the bath she set a syringe through which she pumped droplets of silicone oil of the same viscosity. In each series of experiments, she set the temperature of the hot/cold plate, and measured the temperatures of the oil pumped through the syringe and at the surface of the bath.

Geri used a high-speed camera to record each droplet, at 2,000 frames per second, from the time it was released from the syringe to the time at which it mixed thoroughly with the bath. She performed this experiment using silicone oils with a range of viscosities, from water-like to 500 times thicker.

She found that droplets appeared to levitate on a bath's surface as the temperature gradient between the two fluids increased. She was able to levitate a droplet, delaying its coalescence, by as long as 10 seconds, by maintaining a temperature difference of up to 30 degrees Celsius, or 86 degrees Fahrenheit, comparable to the difference between a drop of cold milk on a bath of hot black coffee.

Geri plotted the data and observed that the droplet's residence time on the bath's surface seemed to depend on the initial temperature difference between the two fluids, raised to the power of two-thirds. She also noticed that there exists a critical temperature difference at which a droplet of a given viscosity will not mix but instead levitate on a liquid surface.

"We saw this relationship clearly in the lab and then tried to develop a theory in hopes of rationalizing that dependence," Geri says.

A cushion's character

The team first looked to characterize the layer of air separating the droplet from the bath. The researchers hypothesized that a temperature difference between the two fluids may influence this air cushion, which may in turn act to keep a droplet afloat.

To investigate this idea mathematically, the researchers performed a calculation, referred to in fluid mechanics as a lubrication analysis, in which they appropriately simplified the complex equations describing fluid motion, to describe the flow of air between the droplet and the bath.

Through these equations, they found that temperature differences between the fluid drop and the fluid bath create convection, or circulating currents in the intervening layer of air. The greater the temperature difference, the stronger the air currents, and the greater the pressure that pushes against the droplet's weight, preventing it from sinking and making contact with the bath.

"We found the force coming from the droplet's weight and the force coming from the recirculation of the air layer will balance at a point, and to get that balance, you need a minimum, or critical temperature difference, in order for the droplet to levitate," Geri says.

Inside a single drop

Next, the team looked for a mathematical explanation for why they observed the 2:3 relationship between the amount of time a droplet levitates on a liquid surface and the initial temperature difference between the two fluids.

"For that, we had to think about how the temperature of the drop changes over time and approaches the temperature of the bath," Geri says.

"With a temperature difference, you generate a flow inside the drop, drawing up heat from the bath, which circulates around until the droplet temperature is the same as the bath and you don't levitate anymore," Bush adds. "We were able to describe that process mathematically."

To do so, the researchers adapted another set of equations, which describe the mixing of two fluids. They used the equations to model a warm parcel of liquid within the droplet that has been warmed by the bath below. They were able to characterize how that parcel of liquid mixed with the colder portions of the droplet, warming the entire droplet over time.

Through this modeling, they could observe how the temperature difference between fluids decreased over time, to the point at which a droplet stopped levitating and ultimately mixed with the rest of the bath.

"If you study that process mathematically, you can show the way in which temperature is changing in the droplet over time is exactly with this power law of 2/3 that we observed in our experiments," Geri says.

Bush says that their results can be used to characterize the spread of certain chemical and biological agents that are transferred through raindrops and sprays.

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