Science / The glass needles in marine sponge skeletons conduct light better than optical fibers
Sophisticated modern technology cannot yet compete with some of nature's creations. These include the sophisticated optical systems developed by sponges. Among the sponges, which are the earliest multicellular creatures, there are those that develop a skeleton composed of glass, hence their name - glass sponges. The lower part of the skeleton is made of glass needles whose optical properties are surprisingly similar to those of optical fibers used in the telecommunications industry. But with one difference: the most advanced man-made technological development has not yet been able to reach the performance of sponge needles.
Between 5,000 and 9,000 species of sponges live in the sea, and there are many more species that exist only in the form of fossils - these are the remains of the ancient sponges. Most of them have an internal skeleton. In living sponges used for bathing, the skeleton is composed of a collagen-like organic material. Other sponges are equipped with a calcareous mineral skeleton, but in most sponges the skeleton is made of vitreous, which is the main component of glass. The glass skeleton can appear in different geometric shapes such as needles, balls, horns, wire and more.
In the glass sponges, the needles are crowded together many times, and a kind of cage is created made of a trellis. This is what happens in the sponge that received the name "Venus' flower basket". With him, the needles were connected to a cylindrical shape and the glass material got a lace texture on the sides. In Japan it was customary to give this sponge skeleton as an engagement gift. The reason for the custom lies in the fact that the living sponge has only one opening for the exit of water, located in the upper part. When the sponge is relatively young, a pair of crabs (male and female) that live in its interior enter through this opening. But the growth rate of the crabs is faster than that of the sponge, and so after a short time the crabs become bigger than the exit door, and they are doomed to end their lives together inside the cavity of the sponge. The choice of their partner is therefore a total commitment, until their last day, hence the symbolism of giving the sponge skeleton with the pair of crabs to the couple about to get married.
"The flower basket of Venus" is the sponge that was used for the research of a multidisciplinary team, and was published last Thursday in the journal "Nature." The team involved Dr. Jeanne Eisenberg, a researcher in the field of nanotechnology who received her doctorate at the Weizmann Institute and now works at Bell Laboratories in New York Rasi, and marine biologist Dr. Micha Ilan from Tel Aviv University. Eisenberg tested the physical and chemical properties of the skeletal needles and discovered that the needles are able to conduct light just like optical fibers, and even like a network of optical fibers. The length of the needles of the "flower basket of Venus" reaches up to 15 centimeters, but they are very thin - their diameter ranges from 40 to 70 thousandths of a centimeter, and they carry tiny "spines" on them, like the stem of a rose. Inside the needle is hidden a core made of organic molecules and it is wrapped in a solid and continuous cylinder made of zinc, which itself is surrounded by a "shell" made of layers of organic material at regular intervals.
"The glass fiber of the sponge looks like a long wire with spikes on it, so when you illuminate it, the light does not run along the central axis only, but splits into spikes and at the end of each spike a point of light is obtained. Thus, from one light source passing through the biological fiber it is possible to obtain a split into a network of many lighting points. These properties give the sponge fibers better optical conduction than the optical fibers used in telecommunications today," says Ilan. One of the problems with industrial fibers is their rigidity, which causes them to break easily. "These biological fibers have organic molecules in the middle that give them flexibility, and even when a crack forms, the fiber does not break. Thanks to the organic component, the fiber can be bent and twisted without breaking it," says Ilan.
The needles of the sponges are created under the conditions of their natural environment, in the depths of the sea where the temperature reaches four degrees Celsius, and under the supervision of enzymes that direct the growth of the material to the characteristic shape of the sponge. These characteristics may make the needles an alternative to current technologies for the production of optical fibers, which require high temperatures. Many studies examine such production directions. Building a fiber at a low temperature allows the introduction of additional elements that affect the transmission of light in the fiber and improves its performance. According to Ilan, "Understanding the biological production pathway of such fibers can contribute to the development of more advanced optical fibers and networks than those in use today."
Now the question remains why a sponge, which lives in the depths of the sea, where no light penetrates at all, needs a mechanism that allows for such sophisticated light transmission? "We know that there are microorganisms in the sea that can produce light. We hypothesized that such microorganisms can live inside the sponge, and thus the light they produce is scattered at many points on the surface of the sponge using the biological fiber system," said Ilan. "In the depths of the dark sea, such a light can attract to it tiny creatures that the sponge filters for its livelihood."
The flower basket of Venus
Light-conducting abilities have been discovered in the creatures living on the seabed, which may be used by the fiber optic industry
Alex Doron, Maariv
The scientists studying nature often come across sophisticated mechanisms, which can serve as a basis for futuristic technology. Take for example the "flower basket of Venus", a special type of sponge (a creature that lives in the depths of the sea), which was recently studied by a team led by two Israelis, Dr. Micha Ilan from Tel Aviv University and Dr. Zhanna Einzberg, a former researcher at the Weizmann Institute and is now a researcher at Bell Laboratories in New Jersey.
The skeleton of the sponge is made of silicon (silicone, the chemical element in glass) and its shape resembles a needle. Its skeletal components are partially joined together to form a network. Thorns come out of the needles, which form a kind of trellis. In the research it was discovered that the needles and spikes conduct light like a sophisticated optical fiber. In fact, their light transmission is even better than that of industrial optical fibers.
Dr. Ilan says that the Japanese usually give the "Venus basket" as an engagement gift. There is an interesting story behind this custom. The sponge is a sedentary (non-mobile) multicellular creature, ancient and primitive, in the form of a cylinder, which looks like lace embroidery. It lives in the depths of the seas and lakes, and has one opening, located in its head. When the sponge is young, a pair of crabs (male and female) enter through this opening, settle in its interior and lead a symbiotic life with it. But the growth rate of the crabs is faster than the sponge, and after a while they are simply trapped inside it. They are therefore condemned to end their lives there, together. The Japanese saw it as a symbol for couples about to get married.
The length of some of the skeletal needles of the Venus basket is 5-15 cm and their diameter is 40-70 microns (thousandths of a millimeter). The sponge is made up of layers at regular intervals, and this structure makes the skeleton needles resistant to breaking even when they crack. They are resistant to bending and large mechanical stresses - which prevents the expansion of the slight crack into a complete fracture
of the fiber.
"Modern technology is still not able to compete with some of the most sophisticated optical systems found in biological organisms," emphasized Dr. Ilan in an interview with Nature magazine. According to him, imitation of these biological properties could in the future lead to the production of high-quality optical fibers, and of modern composite materials.
