FYFD

Category: Research

  • Morphing Wings Using Real Feathers

    Morphing Wings Using Real Feathers

    Although humanity has long been inspired by bird flight, most of our flying machines are nothing like birds. Engineers have struggled to recreate the ease with which birds are able to morph their wings’ characteristics as they change from one shape to another. Now researchers have built a biohybrid robot, PigeonBot, that uses actual pigeon feathers as part of its morphing design.

    Many species of birds, including pigeons, have Velcro-like hooks in the microstructure of their feathers. These hooks help the flight feathers stick to one another and create a continuous wing surface that air cannot easily slip through, even as the wing drastically changes shape. By using actual feathers, PigeonBot shares this advantage.

    PigeonBot also has a somewhat minimalist design in its articulation, using only a wrist and finger joint in each wing to control shape. The feathers are connected through an elastic ligament, which — along with their microstructure — allows them to smoothly change shape under aerodynamic loads. The end result is a remarkably capable and agile biorobot researchers can use to better understand how birds control their flight. (Image and research credit: L. Matloff et al. and E. Chang et al.; via NPR and Gizmodo)

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    Rattlesnakes Sip Rain From Their Scales

    Getting enough water in arid climates can be tough, but Western diamondback rattlesnakes have a secret weapon: their scales. During rain, sleet, and even snow, these rattlesnakes venture out of their dens to catch precipitation on their flattened backs, which they then sip off their scales.

    Researchers found that impacting water droplets tend to bead up on rattlesnake scales, forming spherical drops that the snake can then drink. Compared to other desert-dwelling snakes, Western diamondbacks have a far more complicated microstructure to their scales, with labyrinthine microchannels that provide a sticky, hydrophobic surface for impacting drops. (Video and image credit: ACS; research credit: A. Phadnis et al.; via The Kid Should See This)

  • Tapping a Can Won’t Save Your Beer

    Tapping a Can Won’t Save Your Beer

    It happens to the best of us: sometimes our beer gets shaken up during transit. One common reaction to this is to tap the side of the can repeatedly before opening, but a new scientific study shows that tapping doesn’t affect the volume of beer lost. Danish scientists tested over 1,000 cans of beer in randomized combinations of shaken, unshaken, tapped, and untapped, and observed no difference between tapped and untapped cans.

    The foam-up upon opening takes place in shaken beer because carbon dioxide bubbles form in the pressurized beer, especially along defects in the wall where bubbles can nucleate. When the pressure is released, the carbon dioxide becomes supersaturated and comes out of solution, especially into the pre-formed bubbles, which rapidly grow and overflow. In theory, tapping could disturb those bubbles before opening, but in practice, it makes no difference. Your best bet? Give the beer time to settle before you open it. (Image credit: Q. Dombrowski; research credit: E. Sopina et al.; via Ars Technica)

  • The Physics of Al Dente

    The Physics of Al Dente

    It’s a simple weeknight routine: toss a handful of spaghetti noodles in boiling water, wait a few minutes, and enjoy with the sauce of your choice. But there’s a surprising amount of physics in the humble strand of spaghetti, and a new model focuses on the way spaghetti sags and curls as it cooks.

    Spaghetti, like most pastas, is made of semolina flour mixed with water, extruded (in commercially produced spaghetti), and then dried. Once immersed in water, the rod of pasta begins to swell and soften as water works its way slowly inward. At the same time, it will lose some of its starches to the surrounding water. If the water is hot enough, the pasta undergoes an additional process, starch gelatinization, which is responsible for cooked pasta’s characteristic texture. That perfect al dente condition occurs right as the hydration front reaches the pasta’s core.

    As all of this happens, the initially straight spaghetti strand sags, settles, and curls. Researchers found that, even with a relatively simple model that assumes spaghetti doesn’t stick to the pot, they could capture shape change of individual spaghetti strands, suggesting it’s possible to identify perfectly cooked pasta by shape alone. (Image credit: Pixabay; research credit: N. Goldberg and O. O’Reilly; via Ars Technica)

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    Swinging Jets

    In the tiny realm of microfluidics, flows are, in general, completely laminar. That makes mixing a challenge. But it turns out that pumping water steadily into multiple inlets can spontaneously generate oscillations between the jets, allowing dramatic mixing even at low Reynolds numbers. Two inlets in a parallel channel (first image) oscillate steadily over a small range of conditions, but widening the channels (second image) allows the jets to switch back and forth over a larger range. And adding additional inlets (third image) can create even more complex fluid oscillators! (Image, video, and research credit: A. Bertsch et al.)

  • Flowery Splashes

    Flowery Splashes

    Plunge a disk into water and you’ll get a dome-like splash that closes back on itself. But what happens when that disk has a patterned surface? In this video, researchers added a wedge-like surface pattern to the disk, creating a splash with petals like a flower. Just as the surface of disk is about to submerge completely, a jet of the remaining air spurts out the trough of each wedge. This air jet breaks up the tip of the triangular splashes focused by the wedge. (Image, research, and video credit: H. Kim et al.)

  • Testing Waves in High Gravity

    Testing Waves in High Gravity

    Where waves crash and meet, turbulence is inevitable. But exactly how large waves interact — whether in the ocean, in plasma, or the atmosphere — is far from understood. A new experiment is teasing out a better physical understanding by tweaking a variable that’s been hard to change: gravity.

    To do so, the researchers conduct their experiments in a large-diameter centrifuge (shown above) where they can create effective gravitational forces as high as 20 times Earth’s gravity. This increases the range of frequencies where gravity-dominated waves occur by an order of magnitude.

    By studying this extended frequency range, the authors found something unexpected: the timescales of wave interactions did not depend on wave frequency, as predicted by theory. Instead, those interactions were dictated by the longest available wavelength in the system, a parameter set by the size of the container. It will be interesting to see if future work can confirm that result with even larger containers. (Image credit: ocean waves – M. Power, others – A. Cazaubiel et al.; research credit: A. Cazaubiel et al.; via APS Physics; submitted by Kam-Yung Soh)

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    “Viscoelasticity Gives You Wings!”

    What happens when you drop a hydrogel bead on a water droplet? Because of the hydrogel’s viscoelasticity and its hydrophilic nature, the rebounding bead carries the droplet with it. As seen in the video above, when the impact energy is small enough, the droplet forms a reverse crown during lift-off, kind of like giving the hydrogel bead a skirt. The key feature for lift-off is the bead’s deformation on impact. Because the hydrogel widens at its base, it is sometimes able to push the entire droplet off its initial footprint and detach it from the surface. (Image, research, and video credit: R. Rabbi et al.)

  • Self-Assembly Under Stratification

    Self-Assembly Under Stratification

    Sometimes mistakes lead to great discoveries. After leaving a failed outreach demo overnight, researchers discovered a new mechanism for self-assembling particles. In the initial set-up, a layer of fresh water is poured atop a layer of denser, saltier water. This creates what’s known as a stably stratified fluid, with progressively denser mixtures of salt water as one moves downward. If you pour in particles of an intermediate density (heavier than fresh water and lighter than salt water), they’ll form a layer at one height, and, if you wait overnight, those particles will slowly form a disk-like raft.

    A spheroidal particle causes attractive flow at its equator and repulsive flow at its poles.

    This self-assembly is driven by fluid dynamics — not by any attraction between the particles. Because the particles are unable to absorb salt, their boundaries distort the concentration gradients in the surrounding fluid. This generates subtle currents at the particle boundaries, like in the picture above, where flow moves toward the particle at the equator and away at the poles. Larger particle clusters generate stronger flows, allowing them to attract even more particles.

    Although the speeds involved are quite slow, this mechanism may play an important role in nature, where stratified flows are common. The researchers speculate, for example, that the effect could be important in the clustering of microplastics in the ocean. (Image and research credit: R. Camassa et al.; see also R. McLaughlin; submitted by Kam-Yung Soh)

  • Recreating Volcanic Lightning

    Recreating Volcanic Lightning

    Some natural phenomena, like volcanic eruptions or tornado formation, don’t lend themselves to fieldwork — at least not at the height of the action. The danger, unpredictability, and destructiveness of these environments is more than our equipment can survive. And so researchers find clever ways to recreate these phenomena in controllable ways. The latest example comes from a lab in Germany, where researchers are recreating volcanic lightning.

    To do so, they heat and pressurize actual volcanic ash in an argon environment and let the mixture decompress into a jet, like a miniature eruption. The lightning that accompanies the jet is thought to depend on friction between ash particles, which build up electric charges when rubbed, just like a balloon rubbed against one’s hair. When the charges get large enough, lightning discharges the build-up.

    Small-scale experiments like this one allow researchers to vary the temperature and water content of the ash and observe how this changes the lightning. Drier ash generates more lightning, but it’s hard to distinguish whether this is inherent to the ash or the result of the denser jets that form without the added eruptive force of steam. (Image credit: eruption – M. Szeglat, lab lightning – Sönke Stern/Ludwig-Maximilians-Universität München/Gizmodo; research credit: S. Stern et al.; via Gizmodo)