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Femtosecond laser bionic fabrication enabling bubble manipulation – Phys.org

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The femtosecond laser-induced hierarchical micro/nanostructures promote superhydrophobicity in air and excellent underwater superaerophilicity on the polytetrafluoroethylene (PTFE) surface. Immersing the PTFE surface with superhydrophobic microgrooves in water generates hollow microchannels between the PTFE substrate and the water medium. Underwater gas can flow through this channel. When a microchannel connects two underwater bubbles, the gas spontaneously transports from the small bubble to the large bubble along this hollow microchannel. Gas self-transportation can be extended to more functions related to manipulating bubbles underwater, such as unidirectional gas passage and water/gas separation. Credit: Jiale Yong et al

The manipulation and use of gas in water have broad applications in energy utilization, chemical manufacturing, environmental protection, agricultural breeding, microfluidic chips, and health care. The possibility of driving underwater bubbles to move directionally and continuously over a given distance via unique gradient geometries has been successfully archived, opening room for more research on this exciting topic. In many cases, however, the gradient geometry is microscope and unsuitable for transporting gas at microscope level because most microscale gradient structures provide the insufficient driving force. This makes underwater self-transportation of bubbles and gases at the microscopic level a big challenge.

In a new paper published in the International Journal of Extreme Manufacturing, a team of researchers, led by Prof. Feng Chen from the School of Electronic Science and Engineering, Xi’an Jiaotong University, China, have proposed an innovative strategy for underwater self-transportation of gas along a -induced open superhydrophobic surface with a microchannel width less than 100 µm. The microgroove with superhydrophobic and underwater superaerophilic micro/ nanostructures on its inner wall cannot be wetted by , so a hollow microchannel forms between the substrate and water as the groove-structured surface is immersed in water. Gas can freely flow along the underwater microchannel; that is, this microchannel enables gas transport in water. The superhydrophobic microgrooves make it possible to self-transport bubbles and gases at the microscopic level.

Femtosecond (1015 s) has emerged as a promising solution to prepare such a superhydrophobic microgroove. Leveraging on its two key features: extremely high peak intensity and ultrashort pulse width, femtosecond lasers have become an essential tool for modern extreme and ultra-precision manufacturing. Femtosecond laser processing has the characteristics of high spatial resolution, small heat-affected zone, and non-contact manufacturing. In particular, the femtosecond laser can ablate almost any material, resulting in microstructures on the material’s surface. Thus, the femtosecond laser is a viable tool for creating superhydrophobic microstructures on material surfaces, which is essential for realizing gas self-transportation at microscopic level.

Hierarchical micro/nanostructures were easily produced on the inherently hydrophobic polytetrafluoroethylene (PTFE) substrate by femtosecond laser processing, endowing the PTFE surface with excellent superhydrophobicity and underwater superaerophilicity. The femtosecond laser-induced superhydrophobic and underwater superaerophilic microgrooves greatly repel water and can support gas transportation underwater because a hollow microchannel formed between the PTFE surface and water medium in water. Underwater gas was easily transported through this hollow microchannel.

Interestingly, when superhydrophobic microgrooves connect different superhydrophobic regions in water, the gas spontaneously transfers from a small region to a large region. A unique laser drilling process can also integrate the microholes into the superhydrophobic and underwater superaerophilic PTFE sheet.

The asymmetric morphology of the femtosecond laser-induced ‘Y’-shaped microholes and the unique surface superwettability of the PTFE sheet allowed the gas bubbles to unidirectionally pass through the porous superwetting PTFE sheet (from the small-holes side to the big-holes side) in the water.

Anti-buoyancy unidirectional penetration was achieved; that is, the gas overcame the buoyance of the bubble and self-transported downward. Similar to a diode, the function of the unidirectional gas passage of the superwetting porous sheet was used to determine the gas’s transporting direction in manipulating underwater gas, preventing gas backflow.

The Laplace pressure difference drove the processes of spontaneous gas transportation and unidirectional bubble passage. The superhydrophobic and underwater superaerophilic porous sheets were also successfully used to separate water and gas based on the behavior of gas self-transportation.

Professor Feng Chen (Director of Ultrafast Photonic Laboratory, UPL) and Associate Professor Jiale Yong have identified the significance of the research and the potential applications of this technology (underwater gas self-transportation) as follows:

“How to think of using superhydrophobic microgrooves for gas transportation?”

“Superhydrophobic microstructures have great water repellence, allowing the materials to repel liquids. If a microgroove has superhydrophobic micro/nanostructures on its inner wall, the microgroove will not be wetted by water as the groove-structured surface is immersed in water. Therefore, a hollow microchannel forms between the substrate and water medium. This microchannel enables gas transport in water so that gas can freely flow along the underwater microchannel. The femtosecond laser can easily fabricate such a superhydrophobic microgroove. The width of the laser-induced microgroove determines the width of the hollow microchannel, which is less than 100 μm, enabling us to realize gas self-transportation at microscopic level.”

“Why was femtosecond laser used to prepare such a superhydrophobic microgroove for gas self-transportation?”

“The laser is one of the greatest inventions of the 20th century. In recent years, the femtosecond laser has become an essential tool for modern extreme and ultra-precision manufacturing. Femtosecond laser processing is a flexible technology that can directly write superhydrophobic and underwater superaerophilic microgrooves on the surface of a solid substrate and drill open microholes through a thin film. Furthermore, the track of the open microgrooves and the location of the open microholes can be accurately designed by the control program during laser processing.”

“Does the types of the gas affect the self-transportation of bubbles and gases at microscopic level?”

“Although just the ordinary air bubble has been studied, it should be noticed that the driving force for gas transportation does not involve the chemical composition of the gas. Therefore, the manipulation of gas reported in this paper is applicable to other gases as long as they do not completely dissolve into the corresponding liquids.”

“What are the potential applications of the technology achieving bubble/gas self-transportation and manipulation based on the femtosecond laser-written superhydrophobic microgrooves?”

“We believe the reported methods of self-transporting gas in water along -structured superhydrophobic microchannels will open up many new applications in energy utilization, chemical manufacturing, environmental protection, agricultural breeding, microfluidic chips, health care, etc.”

Researchers also point out that this strategy for self-transporting gas based on the superhydrophobic microgrooves, while validated, is still in its infancy. The influence of various factors (such as the size of the microgrooves, the length of the channel, and the volume of the gas) on the performance of gas transportation needs further research. The practical applications based on the gas self-transportation function also need to be developed.


Explore further

New technology may help repel water, save lives through improved medical devices


More information:
Jiale Yong et al, Underwater gas self-transportation along femtosecond laser-written open superhydrophobic surface microchannels (100 µm) for bubble/gas manipulation, International Journal of Extreme Manufacturing (2021). DOI: 10.1088/2631-7990/ac466f

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International Journal of Extreme Manufacturing

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Femtosecond laser bionic fabrication enabling bubble manipulation (2022, July 27)
retrieved 28 July 2022
from https://phys.org/news/2022-07-femtosecond-laser-bionic-fabrication-enabling.html

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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