“Before, we thought that it was impossible for liquid metal to adhere to non-wetting surfaces so easily, but here it can adhere to various surfaces only by adjusting the pressure, which is very interesting,” said Bo Yuan, a scientist at Tsinghua University and the first author of the study.

Scientists seeking to combine liquid metal with traditional materials have been impeded by liquid metal’s extremely high surface tension, which prevents it from binding with most materials, including paper. To overcome this issue, previous research has mainly focused on a technique called “transfer printing,” which involves using a third material to bind the liquid metal to the surface. But this strategy comes with drawbacks — adding more materials can complicate the process and may weaken the end product’s electrical, thermal, or mechanical performance.

To explore an alternative approach that would allow them to directly print liquid metal on substrates without sacrificing the metal’s properties, Yuan and colleagues applied two different liquid metals (eGaln and BilnSn) to various silicone and silicone polymer stamps, then applied different forces as they rubbed the stamps onto paper surfaces.

“At first, it was hard to realize stable adhesion of the liquid metal coating on the substrate,” said Yuan. “However, after a lot of trial and error, we finally had the right parameters to achieve stable, repeatable adhesion.”

The researchers found that rubbing the liquid metal-covered stamp against the paper with a small amount of force enabled the metal droplets to bind effectively to the surface, while applying larger amounts of force prevented the droplets from staying in place.

Next, the team folded the metal-coated paper into a paper crane, demonstrating that the surface can still be folded as usual after the process is completed. And after doing so, the modified paper still maintains its usual properties.

While the technique appears promising, Yuan noted that the researchers are still figuring out how to guarantee that the liquid metal coating stays in place after it has been applied. For now, a packaging material can be added to the paper’s surface, but the team hopes to figure out a solution that won’t require it.

“Just like wet ink on paper can be wiped off by hand, the liquid metal coating without packaging here also can be wiped off by the object it touches as it is applied,” said Yuan. “The properties of the coating itself will not be greatly affected, but objects in contact may be soiled.”

In the future, the team also plans to build on the method so that it can be used to apply liquid metal to a greater variety of surfaces, including metal and ceramic.

“We also plan to construct smart devices using materials treated by this method,” said Yuan.

This work was supported by China Postdoctoral Science Foundation, the National Nature Science Foundation of China, and the cooperation funding between Nanshan and Tsinghua SIGS in science and technology.

Rhynchosaurs are a little-understood group of roughly sheep-sized ancient reptiles that thrived during the Triassic Period, a time of generally warm climates and tough vegetation.

In the new study, the researchers studied specimens found in Devon and used CT scanning to see how the teeth wore down as they fed, and how new teeth were added at the backs of the tooth rows as the animals grew in size.

The findings, published today in Palaeontology, show that these early herbivores likely eventually starved to death in old age, the vegetation taking its toll on their teeth.

“I first studied the rhynchosaurs years ago,” said team-leader Professor Mike Benton from Bristol’s School of Earth Sciences, “and I was amazed to find that in many cases they dominated their ecosystems. If you found one fossil, you found hundreds. They were the sheep or antelopes of their day, and yet they had specialized dental systems that were apparently adapted for dealing with masses of tough plant food.”

Dr Rob Coram, who discovered the Devon fossils, said: “The fossils are rare, but occasionally individuals were entombed during river floods. This has made it possible to put together a series of jaw bones of rhynchosaurs that ranged in age from quite young, maybe even babies, through adults, and including one particularly old animal, a Triassic old-timer whose teeth had worn right down and probably struggled to get enough nutrition each day.”

“Comparing the sequence of fossils through their lifetime, we could see that as the animals aged, the area of the jaws under wear at any time moved backwards relative to the front of the skull, bringing new teeth and new bone into wear,” said Thitiwoot Sethapanichsakul who studied the jaws as part of his MSc in Palaeobiology. “They were clearly eating really tough food such as ferns, that wore the teeth down to the bone of the jaw, meaning that they were basically chopping their meals by a mix of teeth and bone.”

“Eventually, though, after a certain age — we’re not sure quite how many years — their growth slowed down and the area of wear was fixed and just got deeper and deeper,” added Dr Coram. “It’s like elephants today — they have a fixed number of teeth that come into use from the back, and after the age of seventy or so they’re on their last tooth, and then that’s that.

“We don’t think the rhynchosaurs lived that long, but their plant food was so testing that their jaws simply wore out and presumably they eventually starved to death.”

The rhynchosaurs were an important part of the ecosystems on land during the Triassic, when life was recovering from the world’s greatest mass extinction, at the end of the preceding Permian Period. These animals were part of this recovery and setting the scene for new types of ecologies when first dinosaurs, and later mammals became dominant, as the modern world was being slowly constructed.

By comparing examples of earlier rhynchosaurs, such as those from Devon, with later-occurring examples from Scotland and Argentina, the team were also able to show how their dentitions evolved through time, and how their unique teeth enabled them to diversify twice, in the Middle and then in the Late Triassic. But in the end, climate change, and especially changes of available plants, seem to have enabled the dinosaurs to take over as the rhynchosaurs died out.

Currents can sometimes formulate into circular motions, forming a whirlpool-like phenomena. These are known as eddies, and they are prominent in areas where there are strong gradients in temperature, salinity, or velocity. Their rotating motion can cause nutrients from the colder, deeper waters to rise to the surface.

To investigate the role eddies play in determining the path of the ITF, an international research group has harnessed a high-resolution ocean general circulation model that reproduces eddies. The group featured researchers from Tohoku University, JAMSTEC, Kyushu University, the University of Hawai`i at Manoa, and the National Research and Innovation Agency of Indonesia.

Details of their research were reported in the Journal of Geophysical Research — Oceans on May 14, 2023.

The group’s model enabled them to calculate the transport of simulated particles in a daily-averaged flow field with eddies and a monthly-averaged flow field with smoothed eddy currents, respectively, and estimate the flow rate transported by the simulated particles.

In the Sulawesi Sea, which is situated along the northeastern coast of Borneo and also borders the southern Filipino island of Mindanao, the Sulu archipelago, and Sulawesi Island’s western coast, the group found that large flow fluctuations occur, and seawater circulates over a wider area for an extended period. Seawater also rises from the middle to near the surface, which may cause significant changes in the water when flowing through due to turbulent mixing.

On the eastern side of Sulawesi Island sits the Banda Sea, which surrounds the Maluku Islands and borders the islands of New Guinea and Timor. Here, the current fluctuation is slight, and the model predicted negligible influence from the eddies on the Indonesian Current.

“Our results indicate that the path and residence time of the ITF, along with the mixing process of seawater, must be appropriately reproduced by an ocean general circulation model to gain further insights into and better predict sea surface temperature fluctuations in each region of the Indonesian Archipelago,” points out Toshio Suga, professor of physical oceanography at Tohoku University’s Graduate School of Science and co-author of the paper.

Global warming’s progression is expected to change the ITF. Such changes could have profound repercussions for water temperatures in the Indonesia Archipelago and the Indian Ocean, El Niño and the Indian Ocean Dipole, and the frequency and scale of marine heatwaves that affect marine ecosystems and local weather. Therefore, it is vital to predict accurately such phenomena.

Looking ahead, the group hopes to improve the accuracy of future predictions by clarifying the degree to which eddies impact the path and residence time of the ITF, something quantitatively linked to the determination of water temperature in these areas.

The discovery of these 12,000 -year-old aerophones is extremely rare — in fact, they are the first to be discovered in the Near East. The “flutes,” made from the bones of a small waterfowl, produce a sound similar to certain birds of prey (Eurasian sparrowhawk and common kestrel) when air is blown into them.

The choice of bones used to make these instruments was no accident — larger birds, with bigger bones that produce deeper sounds, have also been found at the site. The Natufians, the Near Eastern civilisation that occupied this village between 13,000 and 9,700 BC, deliberately selected smaller bones in order to obtain the high-pitched sound needed to imitate these particular raptors. The instruments may have been used for hunting, music or to communicate with the birds themselves. Indeed, it is clear that the Natufians attributed birds with a special symbolic value, as attested by the many ornaments made of talons found at Eynan-Mallaha.

The village, located on the shores of Lake Hula, was home to this civilisation throughout its 3,000 years of existence. It is therefore of vital importance in revealing the practices and habits of a culture at the crossroads between mobile and sedentary lifestyles, and the transition from a predatory economy to agriculture. This work² was supported by the Fyssen Fondation and the ministère des Affaires étrangères.

Notes

1. The team is co-directed by Laurent Davin (post-doctoral researcher at the Fyssen Fondation) and José-Miguel Tejero (University of Vienna, University of Barcelona) and includes scientists from the Centre de recherche français à Jérusalem (CNRS/Aix-Marseille Université/ministère de la Culture), the laboratoire Technologie et ethnologie des mondes préhistoriques (CNRS/Université Panthéon-Sorbonne/Université Paris Nanterre), The Hebrew University of Jerusalem (Institute of Archaeology), Israel Antiquities Authority, Virginia Commonwealth University (Department of Forensic Science), École Nationale Vétérinaire (Laboratoire d’Anatomie comparée, Nantes), the laboratoire Archéologies et sciences de l’Antiquité (CNRS/ministère de la Culture/Université Panthéon-Sorbonne/Université Paris Nanterre) and the l’Institut d’ethnologie méditerranéenne, européenne et comparative (CNRS/Université Aix-Marseille).
2. Excavation of the Eynan-Mallaha site is still ongoing, under the direction of CNRS researcher Fanny Bocquentin and Israel Antiquities Authority researcher Lior Weisbrod.