Subtle is artful: nanowires will help create robots the size of molecules

Scientists have developed a new method for producing nanowires — one-dimensional crystals with a thickness of ten thousandths of a millimeter. They are based on compounds of nickel, tantalum and selenium. These materials, unlike their analogues, have shown high stability and resistance to moisture, UV and other influences. The development opens up the possibility of creating superminiature electronic devices, such as robots the size of a molecule. This, in particular, will allow for complex diagnostics. However, experts point out that when implementing and developing the technology, there may be problems with scaling up production.

How nanowires are obtained

Scientists from NUST MISIS, together with colleagues from Tulane University (USA) and Suzhou University of Science and Technology (China), have developed a new method for creating nanowires, crystal structures that are ultrathin filaments.

Photo: Global Look Press/Jochen Tack

These materials make it possible to manufacture miniature electronics. For example, chips or robots the size of one or more molecules. When added to various materials, they endow them with "smart" properties. In particular, such devices will allow changing the transparency of surfaces under the influence of sunlight. In medicine, they will allow for complex diagnostics, as well as effective and quick wound treatment.

As the scientists explained, the new materials are based on compounds of tantalum, nickel and selenium. Their thickness is only from 100 to 400 nm, and their length is up to several millimeters.

— For decades, silicon has been the main material for electronics. However, now developments based on them have reached their technological limit. Further reduction of such devices leads to a sharp deterioration in their characteristics. Therefore, experts are looking for materials that exhibit their electronic properties on a nanometer scale," said Pavel Sorokin, one of the researchers, head of the NUST MISIS Laboratory of Digital Materials Science, Doctor of Physico—Mathematical Sciences.

According to him, the obtained materials belong to the class of one-dimensional crystals. They are long thin "ribbons" of a series of repeating structures. This configuration of atoms provides the material with a high current density and resistance to external influences.

Pavel Sorokin, Head of the NUST MISIS Laboratory of Digital Materials Science, Doctor of Physico-Mathematical Sciences

Photo: NUST MISIS

Despite this, the use of one-dimensional materials is limited. First of all, because of the difficulty of obtaining them, since until now they have been manually separated from large crystals. This is ineffective, and, moreover, such technology does not make it possible to obtain homogeneous and stable structures of sufficient length. Therefore, the materials showed outstanding performance only in the laboratory and were not suitable for mass production of microscopic chips.

— Unlike the traditional approach, where the starting powders are located at one point of the ampoule, in the new technique they were evenly distributed over its entire inner surface using electrostatic charging. Then the ampoule was heated, as a result of which the thinnest crystalline filaments formed on its walls," explained Konstantin Larionov, a researcher at the NUST MISIS Laboratory of Digital Materials Science.

As part of the experiment, the specialists monitored the state of the crystals outside the ampoule at room temperature for a month. Unlike most nanomaterials, which are sensitive to oxidation, moisture, and ultraviolet radiation, their structure has not deteriorated.

Moreover, it turned out that in the future they can be mechanically split into even thinner filaments up to 7 nm thick. This opens up new perspectives, the scientist added. In particular, quantum chemical calculations have confirmed the possibility of manufacturing individual stable miniature structures with semiconductor properties.

Photo: Global Look Press/Cfoto

For example, when interacting with nickel, stable and homogeneous Schottky contacts are formed on the crystal surface. This is the name given to the potential difference between a metal and a semiconductor. These effects are useful for creating photodetectors, solar cells and other devices where sensitivity to an electric field is needed, Konstantin Larionov explained.

According to scientists, the proposed method may open the way to the creation of electronic circuits on a single nanowire. Such crystals can become the basis for many molecular electronics devices.

What devices can be created using nanowires?

For example, ultrathin sensors can be used as part of specialized "smart" surfaces or aerosol clouds in which sensitive receptor molecules change their electrical properties when interacting with target substances.

— Nanowires are often made from materials with high chemical activity. For example, silicon atoms have free electrons that need to be occupied with something. Therefore, they attract extraneous molecules — hydrogen, oxygen and other elements from the atmosphere. These impurities change the properties of materials. In the presented development, the edges of the nanowires are chemically compensated, i.e. inactive. Therefore, unlike silicon, foreign substances stick to them less," Dmitry Kvashnin, a leading researcher at the N.M. Emanuel Institute of Biochemical Physics of the Russian Academy of Sciences, told Izvestia.

Photo: Getty Images/Monty Rakusen

Another advantage of the development is the layering of the obtained materials. This is typical for graphene-type structures, which are obtained from graphite, where the layers are easily separated from each other due to weak electrostatic bonds.

However, these advantages come with technological challenges. The objects are extremely small, and it is difficult to precisely control the mechanical action to split them. The creation of such "jewelry" structures requires high precision.

— Resistance to oxidation, moisture and UV is a rarity for such nanostructures. Such a technological platform opens up opportunities for creating not only individual electronic components, but also full—fledged circuits based on a single nanowire," says Andrey Vinogradov, editor-in-chief of the IT-World portal and the IT Expert magazine.

Photo: Global Look Press/Wolf von Dewitz

He noted that miniaturization is the basis for the progress of modern electronics. By reducing the size of the components, you can reduce power consumption and shorten the signal path, which ultimately increases device performance. The development of such technologies is important for the development of wearable electronics, and especially in the medical field, where the size of sensors and devices is very important.

At the same time, the expert emphasized, during the introduction and development of technology, problems with scaling production may arise, since the integration of such ultrathin elements into industrial processes requires the development of new methods of manipulation and assembly without damaging the structure. It is also possible that new types of defects may appear that will affect the characteristics of the devices. Therefore, it is necessary to study the reliability of nanowires in various conditions, especially in aggressive environments and under mechanical stress, the specialist concluded.