We are not able to fully comprehend nature, and we don’t know how to imitate it in an ideal manner, but we are trying and we’re getting better at it. Engineers spy on mechanisms developed in the course of evolution and put it to good technical use. The effects are often remarkable. Here are six inventions of nature that were copied by humans.
What can be more beautiful than a trail in the woods, sun shining, carriage rolling?
What will the next turn bring, what will fill our surprised eyes?
Mirosław Hrynkiewicz, The Trail in the Woods (O drodze w lesie)
Immaculate in the swamp
For many Asian cultures, the lotus flower is the example of perfection. It symbolizes beauty, purity, sanctity and reincarnation. The beautiful flower grows in muddy rivers and lakes. The leaves of this plant are amazing; although they are often immersed in muddy water, they never get dirty.
The German botanists Wilhelm Barthlott and Christoph Neinhuis explained the unusual self-cleaning capabilities of the lotus. The cells of the external layer of the leaf create protrusions about 20–50 micrometres in size, which in turn have smaller protrusions of 0.5–3 micrometres in size covered with wax crystals, which have a diameter of one nanometre. All this gives the surface a specific roughness; drops of water do not flow along the leaf like rainwater along a window, but thanks to the water’s surface tension they form a ball and roll down collecting any dirt.
Researchers called this phenomenon the ‘lotus effect’. Today, we produce paint, shingles, paper, textiles and automotive care products that take advantage of this phenomenon.
The alluring luciferin
The exceptional talent of a species of beetles, commonly referred to as fireflies, contributed to the development of LEDs. At the beginning of summer (June to July), the female firefly attracts a potential partner with a series of light flashes. The insects emit light by oxidizing a chemical compound called luciferin caused by the action of the enzyme luciferase. This process is incredibly effective and its capacity reaches 98%. (Compare this to the efficiency of a regular light bulb, which usually does not exceed 10%.)
The organ responsible for emitting the light is located on the lower abdomen of the firefly. Before the photons leave the insect’s body, they pass through cuticle layers, and part of them are reflected and go back in. But this is not the case in the genus of fireflies called Photuris. In these insects, the abdomen is covered with tiny scales, which bring to mind overlapping shingles that prevent the light from going back. As a result, the insect emits a light that is 50% stronger than if the scales were to create a flat surface.
International research groups led by Annick Bay from the Université de Namur in Brussels and Ki-Hun Jeong from the Korea Advanced Institute of Science and Technology developed LEDs that apply this observation. The appropriate crimping made on the surface of the diode is a substitute for anti-reflection coating, and is significantly cheaper.
The bird skull
The overload generated when a woodpecker drums its beak on wood at a frequency of 22 beats per second is 1200 times more than the acceleration of gravity. Humans experience concussion already in the range from 80 to 100 g, so how does the woodpecker withstand this? It seems that in the process of evolution, a protection mechanism developed in the woodpecker, which is made up of several elements: a hard yet flexible beak, a resilient hyoid bone that surrounds and protects the skull, bones in the inner part of the skull that have a sponge-like structure, and last but not least, minimum space for the cerebrospinal fluid between the skull and brain.
Based on the example of the woodpecker, Sang-Hee Yoon and Sungmin Park from the University of California Berkeley decided to develop protective layers for airplane ‘black boxes’. They took a steel container (the equivalent of the woodpecker beak), placed an aluminium container in it (that’s the skull), separated the two with thick rubber ribbons (the hyoid bone) and added closely-packed glass spheres (imitating the spongy padding of the brain). A container thus prepared protected the electronics contained within from overloads up to 60,000 g, which is a very good result, considering that the currently applicable standard is 3400 g. We cannot rule out the possibility that this idea could be used in car bumpers or to protect space ships from the impact of meteorites.
Areoles in fog
Cacti have adapted to life in dry conditions in a number of ways. They transformed their stalks and leaves into thick plump formations, thus restricting evaporation. They learned how to collect supplies of water in tissue referred to as water-storage tissue. An important evolutionary modification of cacti is the development of areoles; these are bumps out of which spines, flowers or sometimes even lateral shoots grow. We shouldn’t confuse spines with thorns, as the latter is used for defence only, while spines additionally collect water from fog. The mechanism of this water collection is not simple, but a good description of it was made for the Opuntia microdasys. The areoles of this cactus are set apart by between 7 to 23 centimetres and have 100 spines each. The top part of the spine is covered with a type of burr (looking much like a badly-sharpened pencil) used to catch the water from the fog, while the bottom part has small grooves. Water flows through these cavities to the semi-circle shaped base of the spine, called the trichome; from here it is transferred further on.
Devices that can collect water from fog this way were designed by several research teams from China, Korea and the US. They all use water-repellent surfaces with tiny cones ‘planted’ in them, which are made from a variety of materials: polymers, different metals, nanotubes or MOFs (metal organic framework). The simplest of these machines was built at a university in Beijing and consists of a sphere-shaped sponge with 180 needles made of porous silver. These devices not only collect water from fog, but they also clean it.
To bear a resemblance
A young polar bear has white fur because its hair is transparent, much like the drops of water that create a cloud. The hair is also empty inside, and the fur is light and warm as a result. The thermal insulation properties of the polar bear’s fur are so good that sometimes you can’t see the animal, even through thermal vision cameras.
Following the example of polar bear fur, a research team at the Hefei University of Technology led by Shu-Hong Yu designed a special thermal insulation material. The scientists developed an aerogel (foam in solid physical state) from carbon tubes; it’s a light material that holds heat better than any thermal insulation material known and does not degrade with time. You can compress it to 10% of its volume, and after decompression it still retains its properties. The only drawback is the steep price resulting from the cost of carbon tube production.
Yet another Chinese team from Zheijang University, led by Hao Bai, developed a method to obtain silk fibres that resemble the hair of the polar bear, meaning they are hollow inside. The scientists went on to weave a textile from the fibres, before using it to tailor special clothing for rabbits. It turned out that the textile had exceptional thermal insulation properties, so you can hardly see the rabbits dressed in the clothing in infrared. The army quickly expressed interest in the research and it has since been classified as confidential.
Trembling in the slits
In its arsenal of senses, the tarantula has so-called slit sensilla, or special organs that register mechanical stimulation. They are usually located near the leg joints and consist of small slits in the cuticle, which contain nerve cells. The slits open and close when exposed to vibration, and the nerve cells register these events.
As he was researching the mating customs of tarantulas, Peter Fratzl of the Max Planck Institute in Potsdam observed that they communicate with potential partners by rubbing the leaf they are sitting on, while the object of their advances, even if a few metres away, registers the encouraging vibrations thanks to the slit sensilla.
Man Soo Choi from the National Institute in Seoul read Fratzl’s article and decided to make a copy of the slit sensilla. He coated a 5 × 10 millimetre polymer plate with a very thin (20 nanometre) layer of platinum speckled with irregular slits. When under the influence of acoustic waves, the entire structure gently vibrates, causing changes in electrical conductivity; these are registered in turn by electrodes placed on the shorter sides of the rectangle. If you were to attach such a sensor to somebody’s neck or wrist, you could read off the pulse and register what that person is saying. The plate enables you to distinguish individual words with 98 % accuracy and register very soft sounds, such as the sound made by the wings of a flying ladybird.
Translated from the Polish by Mark Ordon
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