Nature Holds Clues to Improving 3D Design

Posted by Editor On March - 28 - 2017

Presenting a two-part series on how biomimicry paves the way for new, improved structures

Nature Holds Clues to Improving 3D Design

The orange puffball sponge is showing researchers how to build structures that can resist increased pressures without buckling

The thing about learning from nature is that it is a recipe proven in time. Evolution is life’s own method of reiteration, and it does a significant job in refining design to fit needs and circumstances.

Gleaning information from what nature has provided is the essence of biomimicry, the engineering of man-made objects whose engineering was first formed in living creatures.

A number of organisms have been the subject of biomimicry scrutiny for good reason. A good example is the sea turtle. Examination of its interlocking jigsaw shapes of its shell is already lending technique to 3D printing design.

The advent of additive manufacturing has made it easier to replicate these oftentimes complex biological structures. Through the process, scientists are fashioning new insights into object construction and functionality. All of this is leading to better designed helmets and protective gear, lighter and stronger building materials, and even challenging our notions of how we reproduce colors.

Underwater Armor

Nature Holds Clues to Improving 3D Design

The mantis shrimp is providing a treasure trove of engineering design

A keen favorite of biomimicry is the mantis shrimp, of the order Stomatopoda. An unique member of the crustacean family, the mantis shrimp is unlike other shrimp, crabs and lobsters due to the development of dactyl clubs in lieu of claws on its forward legs.

These dactyl clubs operate together like a pair of scissors, giving the mantis shrimp the ability to slice its prey like a ocean floor sushi chef. The mantis shrimp dactyl club is so efficient, in fact, a mantis shrimp can cut through a human finger or glass rod in one strike.

When scientists began studying the mantis shrimp dactyl club up close, they discovered a whole new way of building tensile strength into materials. The herringbone lattice of the calcium-rich cells have shown researchers how the mantis shrimp is able to exert thousands of pounds of punch without fracturing or denting the appendage. This herringbone lattice is now being duplicated in protective gear for motorcycle riders and military with encouraging results.

The dactyl club isn’t the only advantage the mantis shrimp has lent science. In addition to superior shell construction, the eyes of the mantis shrimp have proven beneficial to cancer researchers, as it has been shown that the shrimp is able to see refracted polarized light in a way to visually recognize cancer cells in other animals.

The mantis shrimp isn’t the only animal with its own special protective gear. Scientists are looking at mammals like the pangolin (Phataginus tetradactyla) for insights on how it is able to fashion keratin into dense, lightweight plates. Another animal with a serious coat of armament is the alligator gar (Atractosteus spatula). A ferocious and well-defended type of fish, the gar has ganoid scales of such tensile density they have been known to deflect steel knives. Ganoid scales, found in sturgeons, paddlefishes, gars, bowfin, and bichirs, are made with a layer of dentine and a layer of inorganic bone salt called ganoine which give the fish scales an enamel-like surface.

Strong and Light

An exciting development in ideal construction shapes was recently uncovered by researchers at Brown University. Studies of the orange puffball sponge (Tethya aurantia) have uncovered the ideal shape of thin and flexible rods that resist buckling. It is believed these structures will lend greater industrial strength of everything from building columns to bicycle spokes to arterial stints.

Inside the internal structure of the sponge, which must weather the churn of ocean currents, are the tiny rod-shaped structures that keep the sponge from being crushed.

According to the report: “The rods, called strongyloxea spicules, measure about 2 millimeters long and are thinner than a human hair. Hundreds of them are bundled together, forming stiff rib-like structures inside the orange puffball’s spongy body. It was the odd and remarkably consistent shape of each spicule that caught the eye of Brown University engineers Haneesh Kesari and Michael Monn. Each one is symmetrically tapered along its length — going gradually from fatter in the middle to thinner at the ends.”

Complementing their discovery were structural models found in obscure mathematic journals. Monn and Kesari were able to correlate the engineering ratios of the puffball sponge spicules to designs first uncovered more than 100 years ago.

“This is one of the rare examples that we’re aware of where a natural structure is not just well-suited for a given function, but actually approaches a theoretical optimum,” said Kesari, an assistant professor of engineering at Brown. “There’s no engineering analog for this shape — we don’t see any columns or other slender structures that are tapered in this way. So in this case, nature has shown us something quite new that we think could be useful in engineering.”

The researchers investigated the material composing the spicules and realized that they were nearly pure silicate, making them nothing stronger really than glass. It was the shape of the spicules that were helping the sponge hold its shape.

What substantiated their studies was designs found published more than 150 years ago by a German scientist named Thomas Clausen. According to the article: “In 1851, Clausen proposed that columns that are tapered toward their ends should have more buckling resistance than plain cylinders, which had been and still are the primary design for architectural columns. In the 1960s, mathematician Joseph Keller published an ironclad mathematical proof that the Clausen column was indeed optimal for resistance to buckling — having 33 percent better resistance than a cylinder. Even compared to a very similar shape — an ellipse, which is slightly fatter in the middle and pointier at the ends — the Clausen column had 18 percent better buckling resistance.”

“The spicules were a match for the best shape of all possible column shapes,” Monn said. “It would be easy to 3D-print the Clausen profile into these materials, and you’d get a tremendous increase in buckling resistance, which is often how these materials fail.”

“This work shows that nature can hit an optimum,” Kesari said, “and the biological world can still be hiding completely new designs of considerable technological significance in plain sight.”

The work was supported by the National Science Foundation (1562656). The findings are published in the journal Scientific Reports.

To be continued in Part Two of biomimicry: the structural printing of colors.