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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.


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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

Citation:
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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Jupiter will be its brightest in 59 years Monday. Here's how to see it for yourself – CBC News

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You may have noticed a bright “star” in the eastern sky after sunset, but that’s no star: it’s the mighty planet Jupiter, and it’s almost at its peak brightness.

Jupiter, the largest planet in our solar system, is reaching opposition, an event that occurs when a celestial object rises in the east as the sun sets in the west, putting both the sun and the object on opposite sides of Earth.

But what also makes this special is that the planet will be the closest it has been to Earth in 59 years, meaning it will also be brighter than usual.

The reason planets vary in their distance from Earth is because their orbits aren’t perfectly circular, but rather slightly elliptical.

This image of Jupiter and its moons Io (lower left) and Ganymede (upper right) was acquired by amateur astronomer Damian Peach on Sept. 12, 2010, when Jupiter was close to opposition. South is up and the ‘Great Red Spot’ is visible in the image. (NASA/Damian Peach)

While Jupiter’s opposition happens roughly every 13 months, it’s not common for it to coincide with its closest approach, making this a particularly special treat.

How to see it

At its farthest, Jupiter can be as far as 966 million kilometres away, but on Monday, it will be about 591 million kilometres from Earth. The last time it was this close was in October 1963. And it won’t be this close again until 2129.

You can find the planet in the east after sunset. It’s hard to miss, even from a light-polluted city, as it is the brightest object in the sky. 

As the night progresses, it rises higher into the sky, eventually appearing in the southeast around 11 p.m. ET. on Monday.

You don’t need a telescope or binoculars to see it, but if you do have a pair of binoculars or a telescope, you can have some fun over the coming days. 

One of the special things about Jupiter is its four brightest moons: Callisto, Io, Ganymede and Europa. They orbit Jupiter in a timescale visible from Earth night after night, and even hour after hour — if you’re patient. 

This sky map shows the positions of four of Jupiter’s moons the following night of the opposition, on Sept. 27 at roughly 10:30 p.m. ET. (Stellarium)
This sky chart shows the positions of four of Jupiter’s 80 moons at 10:30 p.m. ET on Sept. 26. (Stellarium)

If you do have a telescope, you can view the moons — and the amazing cloud bands of the gaseous planet, which make for a stunning sight. Also, according to Sky & Telescope magazine, the Great Red Spot will begin its transit — or its crossing — at 8:44 p.m. ET Monday. You can find local times using the publication’s online app or find its app and others like it for your cellphone or tablet. 

Saturn will also be visible in the sky. It currently lies in the south around 10 p.m. ET, but it’s more difficult to spot as it’s not as bright as Jupiter.

You can find several free apps available for download on Android phones and iPhones — such as Stellarium, Star Walk and Sky View — that will help you identify what you see in the night sky, including planets and where to find them.

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NASA Will Crash A Spacecraft Into An Asteroid For Science! – Forbes

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NASA will intentionally crash a spacecraft into an orbiting asteroid at high speed in the coming hours. The DART mission will attempt to prove that an unmanned space probe can autonomously navigate to a target asteroid and intentionally collide with it. The technique, called kinetic impact, could be used to re-direct an asteroids that may pose a threat to Earth, should one ever be discovered.

NASA’s Double Asteroid Redirection Test – a first-of-its-kind experiment – will try to alter the orbit of one of two gravitationally bound asteroids in orbit around the Sun. This binary asteroid system is known as Didymos, and the smaller “moonlet” of the pair, Dimorphos, will be the first asteroid in the Solar System to be the target of a humanmade “kinetic impactor”.

The 1,2 x 1,3 x 1,3-meter space probe will intercept the Didymos system at 7:14 p.m. on Monday, with DART slamming into the 160-meters wide Dimorphos at roughly 6,6 kilometers per second a few hours later if everything goes as planned.

The target asteroid Dimorphos, orbiting the larger Didymos, poses no threat to Earth, and even a successful impact will alter its orbit by just 0,4 millimeters. Any changes in the orbital parameters will be precisely measured using telescopes on Earth. The experiment results will be used to validate and improve computer models for kinetic impacts.

In the last few hours of DART’s life, it will send a constant stream of images to Earth.

“This is an amazing moment for our space program,” so Elena Adams, the mission systems engineer at the Johns Hopkins Applied Physics Laboratory.

“For the first time, we will move a celestial body intentionally in space, beyond Earth orbit! This test goes beyond international borders, and really shows what we can accomplish if we all work together as one team and as one Earth.”

Material provided by the European Space Agency and NASA.

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Squirrels, volcanoes, and ancient DNA – TownAndCountryToday.com – Town and Country TODAY

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ATHABASCA — What does the research into ground squirrels dating back 50,000 years have to do with ancient DNA or volcanoes? 

Those are some of the fascinating details Scott Cocker, a paleoecologist and PhD student at the University of Alberta (U of A), will be discussing in a Zoom presentation hosted by Science Outreach – Athabasca Sept. 27 at 7 p.m. 

“I’m interested in the ground squirrels themselves because we jokingly refer to them as furry botanists,” Cocker said in a Sept. 15 interview. “They were grabbing plants; they were grabbing whatever they could grab before they went into hibernation. So, they would store all this stuff in their nest and then the nest is what we find 40,000 years later or whatever have you … frozen in the permafrost with all those seeds or with bones of other animals. They are basically like little archives of the Ice Age and Yukon.” 

Cocker realized while everyone was distracted by larger creatures like woolly mammoths and woolly rhinos, they didn’t offer as much information on life at the time as ground squirrel nests could. 

“The ecosystem and the environment, we call that the mammoth steppe and for a long time that’s what everyone referred to; the mammoth steppe this, the mammoth steppe that, and it’s just because the mammoths are big and charismatic,” he said. “But my whole thesis is that if you really want to understand the mammoth steppe and the environment that they were living in, you actually have to look to things like the ground squirrels because they tell us way more about the environment than the mammoths do.” 

Throw in some new sequencing of DNA which allows scientists to accurately identify a species from just small pieces of DNA. 

“In the last 20 years, it’s something that’s been developed,” he said. “We can work with modern DNA really easily because stranded DNA are in the count of millions … but once that organism dies and sits around for a while, then the DNA starts to degrade, and it breaks down over time and so we end up with these really short little pieces of DNA.” 

Then mix in the aftermath of a volcanic eruption in southern Alaska 25,000 years ago which covered the area with up to a metre of ash and it changes how all fauna lived and you have the basics of Cocker’s presentation. 

“How did that impact the animals and plants at the time of the eruption? Because it definitely was one of the largest in the last million years in this part of the world,” Cocker said. “It completely covered the plants. Think about (the) ground squirrels or the voles and mice and stuff that … rely on foraging and you’re half the size of the ash fall, you’re gonna struggle.” 

The link to the presentation can be found on the Science Outreach – Athabasca website and social media and will start at 7 p.m. Sept. 27. 

hstocking@athabasca.greatwest.ca 

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