Tag Archives: droplet

Science

Watch thousands of ‘vinegar eels’ swarm through a water droplet in amazing new video

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There’s something strange in the water… a swarm of swirling, squiggling white lines, swimming from the edge of a puddle to the center and back again. They look like bolts of electricity, but they are alive. And they are getting their groove on.

These sentient squiggles are Turbatrix aceti, a species of millimeter-long, worm-like animal known as a nematode. With more than 25,000 species described so far, nematodes are some of the most prolific animals on the planet, Live Science previously reported. Many are parasites. Others, like T. aceti, feed on tiny microbes in pretty much any environment you can think of … including jars of vinegar. Hence, T. aceti‘s somewhat slimy nickname: the vinegar eel.

A team of scientists recently took an interest in vinegar eels not because of where the creatures live, but how they move; like many birds or fish, these unctuous creatures travel in synchronized swarms. To get a better look at the choreography of vinegar eels in motion, researchers watched colonies of thousands of vinegar eels swimming inside water droplets under a microscope. Their results were published Jan. 10 in the journal Soft Matter.

As you can see in the video of the team’s experiments, that choreography is a sight to behold.

After roaming the droplet randomly for the better part of an hour, some nematodes began to cluster at the center, while others swarmed to the water’s edge, racing around the rim like cars in a roundabout. Soon, individual nematodes began undulating their bodies — then, others nearby started to undulate in sync.

Before long, the entire swarm was oscillating, moving in sync to a beat only they could perceive. Lead study author Anton Peshkov, a physicist at the University of Rochester in New York, was astounded by the synchronized complexity of their movement.

“This is a combination of two different kinds of synchronization,” Peshkov told ScienceNews.org. “Motion and oscillation.”

One final surprise remained. As the swarm swam in unison, it pushed against the edge of the droplet, temporarily preventing the droplet from contracting as it slowly evaporated. When the team measured the force exerted by the roiling nematode horde, they found that the worms had the potential to move objects hundreds of times their own weight.

Perhaps this video can serve as a reminder that one should not underestimate the nematodes. One worm in your vinegar bottle might be an inconvenience — but a thousand worms in your bottle is a flash mob in the making. Good luck stopping that party.

Originally published on Live Science.

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Health

Exposure to one nasal droplet enough for Covid infection – study | Coronavirus

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Exposure to a single nasal droplet is sufficient to become infected with Covid-19, according to a landmark trial in which healthy volunteers were intentionally given a dose of the virus.

The trial, the first to have monitored people during the entire course of infection, also found that people typically develop symptoms very quickly – on average, within two days of encountering the virus – and are most infectious five days into the infection. The study was carried out using a strain of the virus before the Alpha, Delta and Omicron variants emerged.

The trial’s chief investigator, Prof Christopher Chiu, of Imperial College London, said: “Our study reveals some very interesting clinical insights, particularly around the short incubation period of the virus, extremely high viral shedding from the nose, as well as the utility of lateral flow tests, with potential implications for public health.”

The findings, published on Springer Nature’s pre-print server, and which have not yet been peer-reviewed, detail the outcomes in 36 healthy, young participants with no immunity to the virus. The volunteers were monitored at a specialist unit at the Royal Free hospital in London, and experienced no severe symptoms.

The study found that the infection first appears in the throat and that infectious virus peaks about five days into infection, by which point the nose has a much higher viral load than the throat. The study also suggested that lateral flow tests are a reassuringly reliable indicator of whether infectious virus is present. Swabbing the nose and throat makes it more likely to detect infections during the first few days, the work suggests.

“We found that overall, lateral flow tests correlate very well with the presence of infectious virus,” said Chiu. “Even though in the first day or two they may be less sensitive, if you use them correctly and repeatedly, and act on them if they read positive, this will have a major impact on interrupting viral spread.”

The team say the trial paves the way for future challenge studies that could help accelerate the development of the next generation of vaccines and antiviral drugs.

Prof Sir Jonathan Van-Tam, the deputy chief medical officer for England, said: “Scientifically, these studies offer real advantage because the timing of exposure to the virus is always known exactly, therefore things like the interval between exposure and the profile of virus shedding can be accurately described. This important study has provided further key data on Covid-19 and how it spreads, which is invaluable in learning more about this novel virus, so we can fine-tune our response.”

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Science

Scientists Smash Temperature Record on Keeping ‘Freezing Cold’ Water in Liquid Form

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Scientists have just proven that the freezing temperature of water can be even lower than what we thought was possible.

Taking tiny droplets of water, up to just 150 nanometers in size, a team of engineers at the University of Houston has pushed the critical temperature threshold to -44 degrees Celsius (-47.2 degrees Fahrenheit) – and, more saliently, accurately measured it.

 

Not just a fun thing to brag about at engineering parties, this achievement can now help us to better understand how water freezes, which has implications for a range of scientific fields, from meteorology to cryopreservation.

“Experimental probing of the freezing temperature of few-nanometer water droplets has been an unresolved challenge,” says mechanical engineer Hadi Ghasemi of the University of Houston, Texas.

“Here, through newly developed metrologies, we have been able to probe freezing of water droplets from micron scale down to 2 nm scale.”

Most of us don’t think about water very much, because it’s so ubiquitous and essential for our very existence. But common H2O is actually pretty weird; it doesn’t behave like any other liquid. Even the way it freezes is weird: where other liquids increase in density as they cool, water actually becomes less dense as it freezes.

Water’s behavior has been fairly well characterized and studied. We know, for example, that it tends to nucleate, or form ice crystals, at a variety of temperatures, sometimes resisting the process as far as -38 degrees Celsius. Any colder, and even the most stubborn water molecules will stick together as ice.

 

Ghasemi and colleagues pushed that temperature downwards by placing nanodroplets of water on a soft surface, like a gel or a lipid. Then, they probed the droplets using electrical resistance metrology and Fourier transform infrared spectroscopy to take their temperature as they froze.

The soft interface between the surface and the tiny droplet seemed to play a role in the suppression of ice nucleation, possibly because of the way the interface generates a large pressure on the droplet.

This is because the freezing temperature of water drops as ambient pressure rises. The most pronounced effect was seen in a droplet of water just 2 nanometers across.

“We found that if a water droplet is in contact with a soft interface, freezing temperature could be significantly lower than hard surfaces,” Ghasemi explains.

“Also, a few-nanometer water droplet could avoid freezing down to -44 degrees Celsius if it is in contact with a soft interface.”

The way tiny water droplets freeze is vitally important to cryopreservation, since the freezing of tiny droplets within cells can cause those cells to rupture and die. Learning how to slow or halt that process could help scientists find ways to mitigate that effect.

 

It could also help us better understand how nucleation happens in the atmosphere, where microscopic droplets of water freeze. And it could also help us to better design technology that suffers from ice exposure, such as aircraft and wind turbines, the researchers said.

“The findings are in good agreement with predictions of classical nucleation theory. This understanding contributes to a greater knowledge of natural phenomena and rational design of anti-icing systems for aviation, wind energy, and infrastructures and even cryopreservation systems,” they write in their paper.

“The findings provide an understanding of various natural phenomena and provide a route for the design of superior anti-icing biomimetics or smooth liquid-infused surfaces.”

The research has been published in Nature Communications.

 

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Science

Amazing Video Reveals a New Kind of Leidenfrost Effect We’ve Never Seen Before

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Above 193 °C (379 °F) something almost magical happens to water in a pan.

Called the Leidenfrost effect, when you sprinkle water onto a hot surface, the drops float above the surface on a layer of vapor. They stick around for a moment or two longer than they would at a lower (but still above boiling) temperature, skittering across the pan before evaporating away.

 

This happens to all different types of liquids, as long as the temperatures are much hotter than each particular liquid’s boiling point. But researchers have just discovered something even more interesting – that this effect can occur even between two droplets of different liquids, causing them to ‘bounce’ off each other.

The team of researchers, led by first author, University of Puebla physicist Felipe Pacheco-Vázquez, looked at liquids such as water, ethanol, methanol, chloroform, and formamide, and analysed whether two drops of each combination of liquids would ‘coalesce’ straight away into a single droplet, or would ‘consecutive rebound’ (bounce off each other a few times).

They did this by using a small metal plate with a slight inward slope and heating it to 250 degrees, which was well above any of the liquids’ boiling points (which ranged from acetone’s 50 °C to formamide’s 146 °C at the lab’s altitude).

A big clear drop of one liquid was then added with a small blue dyed drop and they watched what happened. Some – when both drops were the same type of liquid or liquids with similar boiling points – just merged straight away, once they slid into each other at the lowest point of the plate.

Others took their time before merging. They looked a lot like the small droplet bouncing on the big one. You can see this between ethanol (the small droplet) and water (the big droplet) below in the video:

 

“The direct coalescence lasts some milliseconds, and it was observed mainly with drops of the same liquid (e.g. water-water) or liquids with similar properties (e.g. ethanol-isopropanol),” the team writes in a new paper.

“In contrast, drops with large differences in properties (e.g. water-ethanol or water-acetonitrile) remain bouncing during several seconds, or even minutes, while they evaporate until reaching a critical size to finally coalesce.”

 

Eventually after the liquid that evaporates faster shrinks to a particular size, the two drops combine and then ‘pop’ – you’ve got one slightly bigger mixture of liquids skating around instead of two.

You can see from the table below whether any of the two liquids coalesced (c), rebounded (r), did some combination of both (c/r), or in special cases remained as separated phases because they can’t be mixed (s).

 Outcome of the collision of two Leidenfrost drops. (Pacheco-Vázquez et al., PRL, 2021)

The team suggest that this bouncing is actually a ‘triple Leidenfrost effect’, where the drops don’t just end up with an insulating vapour layer from the surface of the hot plate, but also between the two droplets.

“The bouncing dynamics is produced because the drops are not only in Leidenfrost state with the substrate, they also experience Leidenfrost effect between them at the moment of collision,” the team writes.  

“This happens due to their different boiling temperatures, and therefore, the hotter drop works as a hot surface for the drop with lower boiling point, producing three contact zones of Leidenfrost state simultaneously. We called this scenario the triple Leidenfrost effect.”

The research has been published in Physical Review Letters. 

 

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