The artificial spider cores may yet build the next generation of computers

Researchers have previously succeeded in weaving thin fibers like spider webs. Recently, two researchers from the Technion made a breakthrough: they managed to weave such fibers, which are also extremely strong, and weave them. The possible applications are many and varied: sensitive detectors for dangerous chemical substances, huge space sails, and more

By: Yuval Dror

The spider is a strange animal. It captures its prey using a web. The fibers that the spider weaves are thin and strong and scientists have been trying for many years to imitate this ability of the spider. Prof. Eyal Sussman and his colleague Prof. Alexander Yarin began five years ago to engage in technology, which makes it possible to produce tiny artificial spider webs. "It simply intrigued us to deal with nanometric elements," explains Sussman. Since then, the two have succeeded in developing artificial spider webs that may be used as sensitive biological detectors, as huge space sails and as tiny conductors for computer chips. So far, the commercial potential has not been realized.

"We don't have free time to contact commercial companies", says Sussman, but adds that they are in contact with several companies in the hope that the development will be integrated into a commercial product.

Sussman and Verin, professors of mechanical engineering from the Technion, are engaged in the field of nanotechnology. The orders of magnitude in this field are confusing because they are so small. One nanometer is one billionth of a meter. For comparison, the diameter of a human hair is about 40 microns, that is about 40 millionths of a meter. In the mid-90s, President Bill Clinton ordered the transfer of hundreds of millions of dollars to research in the field of nanotechnology and brought about a huge boom in the field. In Israel, too, several centers have been established that research materials and processes at the nanometer level. However, unlike the centers in the US, none of them were established with government aid.

In recent years, several groups around the world have begun to develop spider webs under laboratory conditions. The reason for this lies in the special properties of spider webs: they are thin but strong. While the spiders use a clear, thick and sticky liquid made up of different proteins to produce the thin silk webs, Sussman and Virin use a polymer solution - a chemical substance made up of large molecules.

The polymer solution has two important properties: it is viscous and flexible. Therefore, when it is stretched, fibers are formed. The two looked for a sophisticated method to create the fibers and chose the electronic spinning technique. This method was invented in the 30s, but it did not find many applications. Now, Prof. Yarin explains, the appropriate application for it has been found.

And this is how it works: the polymer solution is inserted into a syringe with an electrode inside. The syringe very slowly pushes the solution until a hemispherical drop forms at its tip. From the moment the voltage inside the syringe is increased to tens of kilovolts, the polymer solution is charged with an electric charge. The electrical forces acting on the drop pull it down until it stretches into a cone. From this cone comes out a thin fiber, which is piled on a surface under the syringe. The diameter of the fibers ranges from several tens of nanometers to one micron, depending on the type of polymer used. The fiber is collected randomly and is not woven.

This is how the drone will be improved

So far there is no novelty in the development of the two. Other places also know how to produce such fibers. But recently the two have taken an important step forward. The fibers that pile up at the bottom of the syringe are in a strong electrostatic field. The two built a kind of lens that serves as a lightning arrester, or rather - a fiber arrester. The fibers are drawn to the lens, which is able to weave them in any way you choose: as a rope, two and three and more.

"This was our breakthrough," says Prof. Sussman. "In most of the developments that preceded us, they knew how to produce a block of fibers, which they used as a filter. We were able to weave the fibers in a systematic way and thus create a structure of fibers and not a shapeless lump". The reason why the requested application of the unordered nanometer fibers is a filter lies in the properties of the "block" that is obtained. On the one hand it is tiny in size and on the other hand its surface area is several thousand times larger than the visible surface area. The result is a sensitive filter, capable of filtering dust or biological substances.

The fact that the two developed a way to tell the fibers how to arrange themselves in space opened up a whole world of applications for them. Working together with Prof. Daniel Weiss from the Technion, the two created a tiny aerodynamic mat, a kind of parachute based on a sheet of nanometer spider webs. The diameter of each small parachute is about one centimeter. The fibers were prepared in such a way that they contained a component that was sensitive to some biological substance. When they encounter this substance, they change color.

"This is not a curiosity," emphasizes Sussman. "This development can allow military forces to disperse dozens or hundreds of such parachutes from the air, which will monitor the presence of biological or chemical substances in a certain area. If the fiber encounters a substance, it changes its color or transmits some kind of transmitter to the forces behind it." Another military application is shielding soldiers by coating their uniforms with the thin fibrous material. The fibers will allow the soldiers to quickly distinguish if they come across a dangerous chemical or biological substance and even stop and neutralize the biological or chemical contamination.

Another development with security implications is related to the strength of the resulting fibers. "The force that needs to be invested in tearing real spider webs ranges from 1 to 10 grams per fiber (depending on the type of spider that weaves the webs). In the fibers we have produced so far, you only need to invest 0.1 gram to tear them. This means that we have not yet approached the strength of real spider webs," says Sussman. To strengthen the fibers, the two formed a collaboration with Prof. Yachin Cohen from the Faculty of Chemical Engineering at the Technion. Together they managed to develop a mechanism that threads carbon tubes inside the polymer fibers, which significantly strengthen the fiber. Threading the carbon tubes is not complicated. All that is needed is to insert them into the polymer solution. During the pushing of the liquid through the syringe, the cannulas are injected into the fine fibers.

"Stronger fibers will make it possible to build drones (tiny pilotless planes) that are lighter but just as strong," explains Sussman. "This combination will allow the UAV to save fuel and thus be able to stay in the air for a longer time." Indeed, projects with a distinct military potential are partially financed by the defense establishment. Next week representatives of the US Army will also arrive at the Technion to examine the development of Sussman Virin.

This is how the spacecraft is driven

"We have technology, we have a method to weave the fibers, now we just have to find the appropriate applications," says Sussman. Indeed, these days the two, together with a group of doctoral students, are busy experimenting with different polymers, some of which have electrical conductivity, trying to see what they can get out of them.

Recently, the two began working together with Prof. Oded Jordan from the Faculty of Agriculture of the Hebrew University in Jerusalem, with the aim of experimenting with polymer fibers produced in the presence of fungicidal substances. Almost any substrate can be coated with these fibers. For example, these fibers can be used as a means of protection against mold fungi, which damage agricultural produce in storage. The idea may also be integrated into medical uses, mainly in the use of fiber-combined bandages as another means of reducing the chance of infection from factors such as bacteria or fungi.

In a field where the development of artificial fibers has enormous commercial potential, there are companies capable of supporting the commercialization of the development. These are nanometer fibers capable of being used as conductors. Every electronic board has tiny copper wires that conduct the electrical current from one component to another. These are wires that are several hundred nanometers in size. But the electronics industry is approaching a limit where it will no longer be possible to reduce the thickness of the wire with the existing methods. "The processor manufacturer 'Intel' currently produces processors with wires with a thickness of 130 nanometers (or 0.13 microns). In our laboratory, with simple methods and with the help of basic technology, we were able to produce polymer fibers with electrical conduction properties, which are only 10 nanometers thick and hundreds of microns long," says Sussman.

According to him, by using electrostatic fields, they manage to direct the fibers so that they are placed in such a way that an electric circuit is formed. "If we 'grandmother's methods' can produce such tiny fibers that conduct electricity, imagine what 'Intel' can do with the technology. In fact, this ability opens up a new field known as nanoelectronics," says Sussman. If a company like "Intel" or "Applied Materials" (Applied Materials), which is considered the world's largest manufacturer of machines that print electronic circuits, decides that Sussman and Verin's technology can be used commercially, then it may be the basis of all electronic circuits in the next decade.

The ideas of the two do not end here either. According to them, another possible application of their spider webs would be in space. For a long time, the possibility of building a spaceship equipped with a solar sail has been examined. The "wind" that will drive the spacecraft will actually be the energy produced by the impact of the photons on the sail. According to the design, the spacecraft will know how to move the sail in relation to the sun so that the source of energy that drives it will not die out.

However, beyond the theoretical problems, which have not yet been clarified in depth, there is a practical problem: how do you move a space sail, whose area must be several hundred square meters so that the energy of photons can move it, into space. "Our idea is not to move the sail into space but to weave it in space," says Sussman. "All that needs to be done is to transfer the raw materials and the production machines and then start and produce the sail in the space of the required size and shape." They intend, says Sussman, to try and propose this idea to NASA personnel in the near future.

Spider secrets: Scientists have discovered how webs are made

The spider's web is stronger than steel and flexible like rubber * The discovery will allow the development of body-fitting protective vests

31.8.2003

By: Alex Doron

Humans have been using silkworms for over 2,000 years, without understanding how the silk fibers themselves are made. The web of the spider's web is known to be stronger than steel and flexible like rubber, in addition to its great advantage of its light weight.

A team from Taft University in Boston, headed by bioengineering expert Prof. David Kaplan, announced yesterday that they discovered how the worms and spiders control the glands that produce the proteins, for spinning the webs. A report on the research is published this morning in the science weekly Nature.

The production of the spider's web has until now been considered an even more unknown puzzle, and cracking it is considered a particularly significant achievement. Understanding the process will serve as a basis for a new generation of lightweight, strong and very rigid materials and products, such as personal protective vests or clothing for medical teams in hospitals. Following the discovery, they began raising a herd of goats in the United States that underwent endogenetic changes, so that their bodies produce milk that contains the proteins needed to create the spider's webs or the fibers of the silkworms.

A spider is able to weave in one morning a web whose fibers are 30 meters long. Scientists observed a spider that "in one pull" and without stopping, weaves a web that is 300 meters long.

For information in Nature