More than seventy years ago, American physicist Feynman put forward a great idea:
"If one day, the atoms can be arranged according to people's will, what kind of miracle will happen?"
Feynman deserves to be regarded as the greatest master of quantum mechanics, because he knows that the physical, chemical and biological characteristics of matter are very different from those of original matter on the microscopic particle scale. Therefore, if we can reconstruct the atomic arrangement of matter, we can completely change the nature of matter, which will have a far-reaching impact on the future fields of science and technology, engineering and medicine.
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Carbon is a very magical element. It has some metallic properties (the ability of atoms to lose electrons) and some nonmetallic properties (the ability of atoms to gain electrons), but these two properties are not strong, so carbon has an ambiguous state.
This neutral atomic state eliminates the chemical polarity of carbon atoms. Without polarity, there are more possibilities:
Carbon is not the most abundant element on the earth (ranked 12), but it has the most abundant compounds among all elements.
Therefore, most important compounds on earth are inseparable from carbon. For example, amino acids are carbon chains based on carbon elements, and deoxynucleotides, the basic unit of DNA, are also long carbon chains. All life on earth can be called carbon-based life.
In our daily life, we often come into contact with many carbonaceous substances, from soft graphite to the hardest diamond. Although the constituent substances are all carbon elements, their material characteristics are completely different because of the different arrangement of carbon atoms.
The output and price of diamonds make it impossible to enter the homes of ordinary people. When scientists separated graphite, they found that its carbon atoms were closely connected, forming a two-dimensional honeycomb lattice structure. Scientists call this carbon atom structure graphene, which has many magical properties:
For example, when it is damaged, it can repair itself only by contacting with substances containing carbon atoms; It has ultra-high light transmittance and looks almost transparent; It has extremely high mechanical, electrical and thermal properties.
All these excellent characteristics make scientists salivate, but even if we are fully aware of the characteristics of this material-it has an unusual structure on the micro scale, it is very difficult to manufacture them.
Simply put, if a thin layer as thick as 1 carbon atom can be torn off from the surface of graphite sheet, graphene can be obtained.
However, even though scientists have tried various methods, including redox method, directional epiphysis method, chemical vapor deposition method and so on. However, the graphene produced by these methods is not uniform enough or the cost is too high.
Until 2004, British scientists Andre Geim and Konstantin Novoselov invented a very simple method-"mechanical stripping method":
It is to peel off the graphite sheet from the highly oriented pyrolytic graphite, then stick both sides of the graphite sheet on a special adhesive tape, and tear the adhesive tape to split the graphite sheet in two. Repeatedly repeating this operation, the graphite sheet becomes thinner and thinner. Finally, the tape is dissolved with a solution to obtain a sheet consisting of only one layer of carbon atoms, which is graphene.
With this simple and effective method of "tearing tape", two scientists won the Nobel Prize in Physics in 20 10.
However, this method of preparing graphene still has defects:
Theoretically, graphite can always be divided into two parts by using adhesive tape, but the glue on the adhesive tape is not always uniform, which will lead to the destruction of the integrity of graphene, so the graphene prepared by this method is usually a few microns in size.
It seems that human beings have only seen a glimmer of light if they want to acquire new materials in a microscopic state. ...
Fortunately, however, there is a technology-"lithography", whose processing accuracy has reached the nanometer level (1 atom is about 0. 1 nanometer), which has been developed very maturely and reliably:
In this method, semiconductor silicon is irradiated with ultraviolet light, and a fine to nanometer circuit diagram is engraved on the surface of silicon single crystal through photochemical reaction and chemical physical etching.
The silicon wafer processed by lithography can also be counted as a special material, because the silicon wafer can have magical functions such as transmission, calculation and storage after being electrified (with the cooperation of software) by processing fine microstructure to nanometer level.
However, there is a difficulty at present. When the machining accuracy of silicon wafer exceeds 5 nm, it has reached its physical limit, which leads to the tunneling effect of electrons. At this time, the chip will produce uncontrolled leakage phenomenon, which will lead to a significant increase in chip power consumption.
Therefore, in addition to tape tearing and lithography, we need to find another direction to make new materials with magical properties:
"For example, atoms can be directly manipulated to obtain new structural materials."
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In fact, our manipulation of a single atom has long been realized. 1On September 28th, 989, Donne Eigler, a physicist and academician of IBM almaden Research Center, became the first person to control and move a single atom in human history.
On June165438+1October 1 1 day, aigler and his team manipulated 35 xenon atoms with a scanning tunneling microscope and spelled out the letters "I, B, M", thus opening a new era of human manipulation of atoms.
Scanning tunneling microscope (STM) was invented in 198 1. As a scanning probe microscope (resolution is nanometer), it actually has no lens, and the surface of the sample is measured by tunneling current between the needle tip and the sample. It can observe and locate individual atoms. In addition, the biggest contribution of scanning tunneling microscope is:
Under the ultra-high vacuum of 4K(-269. 15) low temperature, a single atom can be precisely manipulated with the probe tip.
By using the tunneling current between the conductive probe tip and the sample surface, the controllable interaction force is provided for the probe tip atoms and the substrate atoms.
However, the materials observed by scanning tunneling microscope must have a certain degree of conductivity, which determines its limitations:
"The observation effect of semiconductor materials is worse than that of conductors, but it is impossible to directly observe insulators."
1985, physicist Gerd Ning Bin, together with Christopher Gabel of the Zurich Research Center of IBM and Calvin Quait of Stanford University, invented an atomic force microscope, which can observe non-conductors with a similar scanning probe microscope.
This is an analytical instrument, which can be used to study the surface structure of materials including insulators. It belongs to contact microscope. It uses the contact force between the probe and the sample to obtain the surface morphology of the sample. Atomic force microscope also has many advantages:
"Can provide a real three-dimensional surface map; The sample does not need any special treatment, and it can work well under normal pressure and even in liquid environment. It can be used to study biological macromolecules and even living biological tissues. "
Then, the combination of the two will produce an effect greater than 1+ 1 2. On February 2017,65438+3, IBM scientists used scanning tunneling microscope and atomic force microscope to break through an important scientific research achievement:
They manually "beat" the atom with the tip of a scanning tunneling microscope, and successfully synthesized and captured a trialkylene molecule that can exist stably for 4 days for the first time.
For a long time, scientists have always believed that triene molecules can't be synthesized in crystal form at all, because they will polymerize uncontrollably.
Triene is a kind of molecular material composed of hexagonal carbon atoms, which is very similar to graphene, but different from graphene which is unfolded in sheets, it only contains six hexagonal carbon rings and presents a triangular shape.
Because of this unusual arrangement, two unpaired electrons will be produced, which makes trienes easy to be oxidized and difficult to exist stably. Therefore, since 1950, erich kral, a Czech scientist, first predicted sanya alkyl molecules, there has been no artificial synthesis.
Therefore, in order to verify the success of the experiment, IBM team members studied the shape, symmetry, magnetism and other characteristics of the product. The results show that the product does have a triangular structure and can exist stably on the copper surface. The other two unpaired electrons also show a special electron spin phenomenon, which makes the triene magnetic at the molecular level.
Then, since the appearance of graphene, researchers generally believe that graphene is an diamagnetic material-that is, graphene has no magnetism and cannot be magnetized. At present, carbon atoms have a triangular olefin structure and have very unique magnetism. This undoubtedly subverts people's inherent cognition, and even leads to the rise of a field of rewriting history-the era of carbon-based magnetic materials:
"This means that the triangular olefin structure of carbon atoms can be used to build quantum computers and spintronics devices. The result of this operation can further bring more subversive technologies, and the ultimate goal is to be able to manufacture any molecular structure. "
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Of course, there is not only one way to manipulate atoms. 1970, American physicist Arthur Ashkin discovered:
"The force generated by the laser beam can push tiny particles distributed in water or air, and the scattered laser will also generate obvious thrust on the particles."
In 1986, Ashkin made an experiment:
He irradiated the particles with focused laser, and the scattered light of the laser and the laser itself formed a trap to fix the particles like tweezers. This is the famous optical tweezers, and Ashkin is also known as the "father of optical tweezers".
Steven Chu, a colleague of Ashkin in Bell Laboratories and a Chinese scientist, was deeply inspired by this experiment, and he immediately devoted himself to related research.
Chu found that the pressure of laser can slow down and cool down fast-moving atoms and molecules. He uses multiple lasers from different directions to control atoms. 1997, thanks to the method of laser cooling and trapping atoms, Chu Diwen won the Nobel Prize in physics before Ashkin, becoming the fifth China scientist to win the Nobel Prize.
Until 20 18, 96-year-old Ashkin finally won his Nobel Prize. The optical tweezers he invented is also the most promising technical principle to participate in the editing of living cells and even genes:
Optical tweezers can manipulate living matter without contact and damage, and the pressure generated by them is suitable for the study of biological cells, subcellular cells and atomic physics. "
Whenever we think that the development of science has reached the bottleneck, these lovely scientists always let us see new hope. I wish you a bright and prosperous future!
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