In Bio-Inspired Engineering, De Facto Design Science Flourishes
The quiet design revolution continues. It’s called biomimetics, biomimicry, or biologically inspired design. It’s everywhere. From elephants down to individual cells and their components, nature shows the way to get things done. So elegant are natural designs, they have spurred a gold rush by human imitators.
Let’s look at a few recent examples. These all deal with insect designs. We’ll start with the insect that is Günter Bechly’s specialty, the dragonfly.
They call it “glitterwing.” The wing membranes of the male Amazonian dragonfly, Chalcopteryx rutilans, shimmer with shades of red, blue, yellow, and green. The bright colors have sent Brazilian scientists on a hunt to understand the source. Phys.org says that they began the search by studying electron micrographs of the wings.
Brazilian investigators derived partial answers to this question using electron microscopy methods of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Probing the glitterwing color mechanics revealed that the iridescent wings have multiple alternating layers with different electronic densities. The variation of local color was related to the number and thickness of the layers, which changed across the wing. [Emphasis added.]
That was a start, but it didn’t provide data on the chemistry of the wing. For that clue, they teamed up Minnesota experts at Physical Electronics, Inc. (PHI) in Minnesota. Among the interesting findings there was new information about changes in concentrations of sodium and potassium in different layers through the wing’s thickness. The team presented their initial findings at a conference in Tampa, Florida, last week. Apparently there’s a lot more to learn.
The last paragraph of this short article, which begins with a stunning photo of the dragonfly’s colorful wings, makes an important statement about the value of bio-inspired research in general:
“Nature can often provide examples for engineering solutions. The whole field of biomimicry is devoted to learning from nature for potential solutions to difficult engineering problems,” Carr said. “Every natural sample has unique features and a lot to teach us.”
Back in 2013, we wrote about the remarkable gear mechanism in the nymphs of planthoppers. A related family in the insect order Hemiptera (true bugs) made news recently. Leafhoppers employ another design feature worth imitating — two design features, in fact. Another entry on Phys.org says that Penn State engineers are finding a use for a photonic trick used by leafhoppers to escape predators.
Scientists have long been aware that leaf hoppers extrude microparticles, called brochosomes, and wipe them on their wings. Because the particles are superhydrophobic, the leaf hopper’s wings stay dry in wet conditions. What was not understood before the current work is that the brochosomes also allow leaf hoppers and their eggs to blend in with their backgrounds at the wavelengths of light visible to their main predators, such as the ladybird beetle.
Here was a case where artificial design preceded understanding of biological design. The team had created synthetic brochosomes made of microspheres with nanoscale holes. They found that arrays of these spheres “absorb light from all directions across a wide range of frequencies, making them a candidate for antireflective coatings.” This made them wonder if the leafhoppers used their brochosomes for a similar function.
Sure enough, they found that the leafhopper’s brochosomes absorb 99 percent of light hitting them, from ultraviolet to infrared wavelengths. This renders their eggs almost invisible to predators.
Now that they know the trick, the researchers hope that their synthetic antireflective coatings may be used in sensors, cameras, solar cells, and anyplace else where stray light needs to be minimized. The engineered brochosomes “closely mimic the natural ones created by leafhoppers” in geometry and shape, they say in Nature Communications. The open-access paper has an electron micrograph of the soccer-ball-shaped spheres created by the insects, which readers can see look very similar to their manufactured ones. What can one say other than “intelligent design” when the authors mention “design parameters” several times about their work plagiarizing nature?
Those noisy cicadas that emerge in prime-number years are also members of Hemiptera with designs worth swiping. Another team in China is working on antireflective coatings modeled after cicada wings, a third article on Phys.org reports. In this case, the “stealth surface” doesn’t come from brochosome spheres, but from nanostructures on the wings that resemble closely packed cones.
As researchers Imran Zada et al. at Shanghai Jiao Tong University in China explain in a recent issue of Applied Physics Letters, cicada wings have nanoscale structures that give them exceptional antireflective properties, allowing them to transmit or absorb close to 100% of visible light. When it comes to solar cells, antireflective properties play an important role since absorbing more light leads to a better overall performance.
Learning how the finished structures work is one thing, but none of these articles explains how the insects manufacture these devices. How does the insect get from genetic code to finished structure? That would be a fascinating research project in itself. It would seem that the design parameters must be very strict, finely tuned to the wavelengths of light that need to be absorbed.
One more insect design we will look at briefly is honeybee navigation. Another article from Phys.org describes how bees find their way home.
How can a bee fly straight home in the middle of the night after a complicated route through thick vegetation in search of food? For the first time, researchers have been able to show what happens in the brain of the bee.
That brain is really tiny. Packed inside is the ability to interpret optic flow, the constantly changing stream of information during flight. Researchers at Lund University in Sweden knew that bees have “direction neurons” and “speed neurons” but wanted to learn how they work together. The bee brain not only needs to manage the flood of incoming visual information, but also has to be able to store it in a memory to get home. Bees in the rain forest often forage at night, yet somehow are able to fly straight home after work despite a multitude of path changes.
Laboratory experiments with electrodes in the bee’s brain while they navigated “virtual flights” in a simulator allowed the scientists to produce a computational model of path integration. When they tested it on a robot, the model worked. Stanley Heinze was pleased, but also humbled:
He is fascinated by the fact that these insects, whose brains are about the size of a grain of rice and have 100 000 times fewer neurons than human brains, register their convoluted routes, often several kilometres long, and then have no trouble flying the most direct way home again, a task that we humans can only master with the help of GPS devices, despite our huge brains.
Not surprisingly, these articles said nothing about evolution. This may be the way that Darwinism dies a slow, quiet death: by being ignored in the gold rush of design-based research.
Photo: A leafhopper (Alnetoidia alneti), by S. Rae [CC BY 2.0], via Wikimedia Commons.