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Tag: surfactants

  • Deep Breaths Renew Lung Surfactants + A Special Announcement

    Deep Breaths Renew Lung Surfactants + A Special Announcement

    Taking a deep breath may actually help you breathe easier, according to a new study. When we inhale, air fills our alveoli–tiny balloon-like compartments within our lungs. To make alveoli easier to open, they’re coated in a surfactant chemical produced by our lungs. Just as soap’s surfactant molecules squeezing between water molecules lowers the interface’s surface tension, our lung surfactants gather at the interface and lower the surface tension, making alveoli easier to inflate.

    But things are a little more complicated in our lungs than in our kitchen sink because of our constant cycle of breathing, which stretches and compresses our lungs’ surfaces and surfactant layers. Imagine a flat interface, lined with surfactant molecules; then stretch it. As the interface stretches, gaps open between the surfactant molecules and allowing molecules from the interior of the liquid to push their way to the newly stretched interface, changing the surface tension. If the interface gets compressed, some of the excess molecules will get pushed back into the liquid bulk.

    In looking at how lung surfactants respond to these cycles of compression and stretching, the researchers found that the lung liquid develops a microstructure during cycles of shallow breathing that makes the surface tension higher, thus making lungs harder to fill. In contrast, a deep breath like a sigh replenished the saturated lipids at the interface, lowering surface tension and making lungs more compliant. So a deep sigh actually can help you breathe easier. (Image credit: F. Møller; research credit: M.. Novaes-Silva et al.; via Gizmodo)

    P.S. — I’ve got a book (chapter)! Several years ago, I joined an amazing group of women to write two books (one for middle grades and one for older audiences) about our journeys as scientists. And they are out now! In fact, today we’re holding a “Book Bomb” where we aim for as many of us as possible to buy the book(s) on the same day. If you’d like to join (and get ahead on your gift shopping), here are (affiliate) links:

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  • Bubble Trails – Straight or Wonky?

    Bubble Trails – Straight or Wonky?

    Watch the bubbles rising in a glass of champagne and you’ll see them form tiny straight lines, with each bubble following its predecessor. But in a carbonated soda, the bubbles rise all over the place, each following its own zig-zaggy line. Why the difference? A recent study points out the culprits: bubble size and surfactants.

    As bubble size increases from left to right, the bubble trail straightens.
    As bubble size increases from left to right, the bubble trail straightens.

    Looking at a variety of beverage scenarios, researchers found that both a bubble’s size and its surfactant concentration affected what sort of path it followed. For clean (surfactant-free) bubbles, small bubbles take a winding path, but bigger ones move in a straight line. Simulations show that bubbles can only form a straight path if they produce enough vorticity on their surface. Small bubbles just can’t deform enough to do that.

    For bubbles of the same size, increasing the surfactant on the bubbles straightens their path.
    For bubbles of the same size, increasing the surfactants on the bubbles straightens their path.

    When surfactants get added, though, the story changes. For bubbles of a set size, adding surfactants made their paths straighter. This was due, the team found, to a bump in vorticity provided by the stabilizing effect of the surfactants. Champagne, they concluded, has straight bubble paths despite its tiny bubbles because of the drink’s high number of flavorful surfactants. (Image credit: top – D. Cook, experiments – O. Atasi et al.; research credit: O. Atasi et al.; via APS Physics)

  • Soapy Solutions

    Soapy Solutions

    When a drop of soap falls into a pool of water, its surface-loving molecules spread out on the water’s surface. Exactly how the soap spreads depends on the local concentration of its surfactant molecules, which create areas with different surface tensions that cause flow. All in all, it’s a tough process to predict because it varies in time at every point on the pool. But a recent paper offers a new class of exact solutions for the problem.

    The paper considers a surfactant-laden droplet spreading over a (relatively speaking) deep pool. Other researchers showed recently that this situation can be described with a complex version of the Burgers’s equation, which was originally developed to describe turbulent flows. The authors solved the equation for a variety of initial conditions and found that the time-dependent spread of the surfactants was sensitive to the initial surface distribution. The higher the initial surface concentration, the faster the surfactants spread. (Image credit: T. Despeyroux; research credit: T. Bickel and F. Detcheverry; via APS Physics; submitted by Kam-Yung Soh)

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    Within the Bubble’s Pop

    To our eyes, a soap bubble appears to pop instantly, but when observed in high-speed video, the process is far more complex. In this video, the Slow Mo Guys pop human-sized bubbles, giving us an opportunity to appreciate the rupture process at speeds up to 50,000 frames per second.

    Once the rupture starts, the hole spreads very symmetrically. But as the hole grows, the remaining soap film starts distorting. As Gav and Dan observe, the far side of the bubble actually wrinkles up before the rupture front arrives and tears the remaining fluid into droplets! (Image and video credit: The Slow Mo Guys)