Nanotechnology: the best of 2011

The best developments of nanotechnology 2011Georgy Prokonichev, Nano Daizhdest
The outgoing year 2011 turned out to be no less fruitful for various interesting innovations in the field of nanotechnology than the previous one.

"Nano Digest" collected the most interesting achievements of scientists and the main trends of the outgoing year in the field of nanotechnology.

• Nanomachine.

The most remarkable development in the field of nanomachines seems to us to be the project of researchers from the University of Groningen in the Netherlands and the Swiss Research Laboratory of Materials Science and Technology, who created a prototype of a nanoscale "car", which is a large molecule with four symmetrical elements that play the role of wheels. It is fueled by an electric charge coming from the probe of an electron microscope.

A nanomachine measuring 4 by 2 nanometers is placed on a copper substrate and charged with current from an electron microscope probe located above it every half turn of the "wheels". The electrons flowing from the probe cause structural changes in the motor elements of the molecule and cause them to rotate. They rotate only in one direction, so there is no reverse gear for the nanomobile.

• An invisibility cloak made of graphene.

Scientists from the University of Dallas in Texas have invented an invisibility cloak using a well-known natural phenomenon – a mirage. The new material, created on the basis of graphene, has properties similar to hot sand in the desert, which allows you to "take your eyes off" the object, making it invisible. At the same time, invisibility can be turned on and off by sending an electric current through the nanomaterial.

A mirage in nature appears with sudden temperature jumps on the surface of a small area. The rays of light are refracted and fall on the retina of the eye, without being reflected from the surface. Therefore, if an image of a lake appears in front of a person's eyes in the desert, it often turns out to be only a reflection of the blue sky, which was reflected from the hot layer of air near the hot sand.

• Nanoelectronics.

Researchers from Japan and Switzerland have demonstrated the possibility of binding individual molecules together using current-conducting molecular nanowires. This discovery is an important step towards the creation of monomolecular electronics, which will allow us to reduce the size of the electronic devices we are familiar with many times. The key to monomolecular electronics is to combine functional molecules into a single circuit using conductive nanowires. Nanoelectronics will receive a new impetus after this development. There are two difficulties in this task: how to place nanowires in the right places and how to connect them with functional molecules by chemical bonding.

As the initial substrate, the Japanese took a monomolecular film of diacetylene deposited on a graphite substrate. Then a small amount of phthalocyanine was applied to it, from which nanoclusters were formed on the surface of the substrate. At the final stage, the researchers moved the probe of the scanning tunneling microscope to one phthalocyanine molecule and, by applying a pulsating voltage to the probe, initiated chain polymerization of diacetylene, resulting in the formation of a polymer nanowire that can reach another phthalocyanine molecule. According to the creators, this circuit will function as a diode.

• Nanobrain.

The human brain surpasses modern computing systems in many ways. Its structural elements, as is known, are neurons, the number of which in humans is approaching one hundred billion. A unique characteristic of the synapses connecting neurons is their ability to change the effectiveness of communication. In this regard, scientists have been searching for a way to artificially simulate the neural network of the brain for many years. Recently, the staff of Stanford University (USA) announced the creation of a functional model of a synapse based on a material with a slight change in the phase state.

Such materials are often used in the construction of memory elements. The values "0" and "1" in this case are encoded by different resistance levels, between which you can switch by applying electrical impulses that heat the material and cause phase transformation. At high resistance, the state of the substance is amorphous, and at low resistance it turns into crystalline. Scientists managed to achieve an order of magnitude higher resistance difference in both states, which was a necessary condition for simulating a synapse and, as subsequent experiments showed, a circuit based on nodes from such a substance really works like a fragment of a neuron grid.

• Nanogenerator.

Soon it will be enough just to carry the gadget in your pocket and it will recharge from movements – this statement was made by the creators of flat "nanogenerators", which, when compressed, bent or shaken, produce the same voltage as a regular AA or AAA battery. Researchers from the Georgia Institute of Technology have achieved significant success in reducing the size of piezoelectric generators, while maintaining their high energy intensity. Scientists have developed two types of nanogenerators placed in a polymer. Each of them is a stack of thin sheets connected by nanowires of piezoelectric zinc oxide, several hundred nanometers thick.

In one prototype, the space between the nanowires is filled with plastic, and the entire structure is located between two plates of electrically conductive material. With a slight compression, it generates a voltage of about 0.24 V. The other generator contains more nanowires and generates 1.26 V, that is, it approaches the voltage of a standard battery or accumulator.

• Nanomedicine and prevention.

Scientists from the University of Iowa managed to use nanoparticles to shed light on the complex processes occurring inside the elements of a living cell. All elements of the cell, in fact, can be called natural nanomechanisms, but currently scientists have a very vague idea of how exactly they perform them. The Americans identified and investigated several types of basic movements occurring in intracellular nanomachines.

Nanomedicine makes it possible to develop new diagnostic methods. Translational movement is easy to track with the help of modern microscopes. However, rotational motion is much more difficult to observe due to the limitations of observational technology, as a result of which many processes based on rotational molecular movements are still poorly understood. Then the scientists introduced gold nanorods into the cell, the dimensions of which are 25 nm in diameter and 75 nm in length, which were dispersed throughout the cell. Then, using interference contrast microscopy, they were able to measure both their position and movement and simulate on a computer a complete three-dimensional picture of the movements taking place in the cell. The results of their research can help in the treatment of various serious diseases, such as Alzheimer's disease, as well as advance research in the field of artificial modeling of intracellular processes.

• Nanosensor.

Scientists from Stanford University have developed an innovative biosensor chip that allows diagnosing cancer at an early stage. The sensor designed by Professor Shang Wong and his colleagues is based on magnetic detection nanotechnology and is capable of detecting a given cancer biomarker protein at a concentration of one in a hundred billion (that is, 30 molecules per cubic millimeter of blood). Such a sensor is almost a thousand times more sensitive than the currently used technologies for diagnosing the initial stages of tumor development. In addition, its work is equally effective in any biological fluid in which doctors need to determine the presence of a cancer biomarker – in saliva, plasma and serum, urine or lymph. The effectiveness of the nanosensor chip has been confirmed by experiments on mice. At the same time, according to scientists, the sensor can be configured to search for a variety of biomarker proteins and, accordingly, detect not only cancer, but also many other diseases.

• Nanobot.

Korean scientists announced the development of a new technology for controlling medical micro-robots in the human body. Many scientists and science fiction writers have written about the prospects of microbots or even nanobots. Moving with the blood flow, micromachines could perform the most difficult work, deliver medicines, kill cancer cells and bacteria, destroy blood clots and other formations that cannot be reached in any other way. However, at present, the problem remains not only the construction of some nodes of microbots, but also their management.

Researchers from South Korea have proposed using an external magnetic field to create two different types of nanorobot movements: "screw", or corkscrew-like, and translational. In the first case, the robot will be able to move forward/backward and "drill" or otherwise destroy blood clots. In the second – to fold into the right blood vessel at the site of the artery branching and perform other maneuvers associated with movement in the circulatory system. During the tests carried out in a mock-up of a blood vessel filled with water, scientists confirmed the effectiveness of this method of controlling a micro robot.

• Growing organs.

The idea that organs can be grown for transplantation is not new, but there are a number of obstacles to its implementation. Organs cannot be grown like a piece of skin in a Petri dish, they need a volumetric matrix, a kind of framework for growth. However, scientists from Rice University have proposed a completely different way – to grow organs in a suspended position using a magnetic field. The implementation of this method is carried out by the n3D Biosciences laboratory. With the help of bacteriophage viruses, a patented mixture of nanoparticles called Nanoshuttle is delivered to the cell. These particles inside the cells react to the influence of a magnetic field, which allows you to control the growth of tissue in three dimensions. In such a suspended position, cells can live and multiply, forming three-dimensional structures, according to the program embedded in the DNA. Cell culture will develop naturally, much better than at the bottom of a flat petri dish. This means that the cells will function in laboratory conditions as in living nature. During the experiments, n3D Biosciences specialists have already managed to grow embryonic kidney cells (HEK293), which can be used for rapid wound healing and testing of certain drugs.

• Restoration of spinal tissue.

A joint group of scientists from Italy and the USA managed to achieve significant success in the field of spinal tissue restoration after injuries. Usually, after fractures, a scar forms at the site of injury that does not transmit biological currents, as a result of which a person is partially or completely paralyzed. Scientists have put forward the idea of growing a multitude of tiny parallel tubes with the help of supporting nanostructures, in which new nerve tissue would grow. Such structures made of tubes 2-3 mm long and 0.5 mm in diameter were formed from biodegradable polymers, while the inner surface of the tubules is covered with molecules that play the role of chemical hooks for self-assembly of peptides. The effectiveness of therapy has already been proven by experiments on rats that have restored the mobility of the hind legs after injury for six months, which gives hope to people with paraplegia.

• Restoration of the retina.

Another achievement from the field of nanomedicine is again from Italy, from the Institute of Technology in Milan. Scientists have found a way to restore the damaged retina of the eye using photosensitive plastic.

Creating neuroprostheses is not an easy task, since biological tissues usually do not combine well with electronics and can have a negative impact on the work of nerve cells. Flexible semiconductors became the solution to the problem of artificial retina: scientists seeded the surface of a photosensitive semiconductor polymer with nerve cells that grew and formed complex branched neural networks. During the experiments, it turned out that the polymer coated with neurons can be used as an electrode in a light-controlled electrolytic cell, while it has spatial selectivity. In addition, according to the researchers, it can be configured so that it responds only to light waves of a certain length, which makes it possible to develop systems for treating damaged retina so that color vision is restored.

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It is easy to see that most of the most interesting innovations of 2011 are related to nanomedicine. Perhaps there is some symbolism in this, since the most complex elements of human cells, in fact, are natural nanomachines, and scientists most often do not invent new things, but copy what they have seen from nature. It is possible that such attention to medical developments gives hope that the future of nanotechnology is not military nanobots, but medical robots, and that new technologies will make a person stronger, more agile and healthier, and will not turn him into a working mechanism.

Portal "Eternal youth" http://vechnayamolodost.ru
29.12.2011