3D imaging shows how shark intestines work like a Tesla valve

In 1920, of Serbian origin inventor Nikola Tesla designed and patented what he called a “valve duct “: A hose whose internal design ensures that the fluid will flow in a preferred direction, without the need for moving parts, making it ideal for microfluidics applications, among other uses. According to a recent article published in the Proceedings of the Royal Society B, the Tesla valve also provides a useful model for how food moves through the digestive systems of many species of sharks. Based on new CT scans of shark intestines, scientists concluded that the intestines are naturally occurring Tesla Valves.

“It is high time that modern technology was used to examine these truly amazing spiral shark intestines,” said co-author Samantha Leigh from California State University, Dominguez Hills. “We have developed a new method to digitally scan these tissues and can now examine soft tissues in so much detail without having to cut them out. “

Key to Tesla’s ingenious valve design is a set of asymmetric, interconnected teardrop-shaped loops. In his patent applicationTesla described this series of 11 flow control segments as being made up of “widenings, recessions, projections, baffles, or buckets which, while offering virtually no resistance to the passage of fluid in one direction, other than surface friction, constitute an almost impassable barrier to its reverse flow. ”And because it does this without moving parts, a Tesla valve is much more resistant to the wear and tear of frequent operation.

Tesla claimed that water would flow through his valve 200 times slower one way than the other, which could be an exaggeration. A team of scientists from New York University builds a functional Tesla valve in 2021according to the inventor’s design, and tested this claim by measuring the flow of water through the valve in both directions at various pressures. Scientists found that the water only flows about twice as slowly in the non-preferred direction.

However, the flow turned out to be a critical factor. The valve offered very little resistance at slow flows, but once that flow increased above a certain threshold, the resistance of the valve would also increase, generating turbulent flows in the opposite direction, thus “plugging” the valve. pipe with vortices and disturbing currents. According to co-author Leif Ristroph, this therefore works more like a switch, and can also help smooth out pulsed flows, in the same way that AC / DC converters transform AC currents into DC currents. In fact, Ristroph suggested that perhaps it was Tesla’s intention in designing the valve, given that his greatest fame is to invent both the AC motor and an AC / DC converter. .

And now, the Tesla valve provides insight into the unusual structure of shark intestines, thanks to a team of researchers from three universities: CSU, Dominguez Hills; the University of Washington; and UC Irvine.

the Sharks are advanced predators, feeding on a wide range of species, and are therefore important for controlling biodiversity in the larger ecosystem. Most sharks have spiral intestines made up of a varying number of folds in the intestinal tissue, usually in one of four basic configurations: columnar, spiral, a backward pointing funnel, or a funnel pointing forward. These four types of intestines are typically depicted in 2D sketches that are laid out in two dimensions after dissection or shown as two-dimensional slices through the three-dimensional structure. But that doesn’t give scientists a lot of information about how the structure works in situ.

Last year, Japanese researchers reconstituted micrographs of histological sections from a species of cat shark to a three-dimensional model, offering “a tantalizing glimpse into the anatomy of a spiral-shaped spiral gut,” according to the authors of this latest article. Co-author Adam Summers, of the Friday Harbor Labs at the University of Washington, and his colleagues decided that CT scanning could accomplish something similar, because the technique involves taking a series of x-ray images from different angles and then looking at combine them into 3D images.

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