Molecular Nanotechnology

This article deals with nanotechnology in the original (technical) sense. For nanotechnology regarding the applications of nano-particles, see Nanotechnology .

Molecular nanotechnology ( MNT for short , also molecular manufacturing ) describes a technology at the level of individual molecules .

In 1986 the American engineer Eric Drexler made the term nanotechnology widely known with his book " Engines of Creation ". Drexler defined the term much more far-reaching than, for example, Richard Feynman and Norio Taniguchi before him or than our understanding of nanotechnology today.

Drexler understands nanotechnology to be the digital, programmable manipulation of matter at the atomic level and the resulting production.

His idea and conviction is that a new world can be created from the building blocks of matter, the atoms, according to the Lego brick principle. Because almost everything that is currently imperfect is due to a faulty assembly of atoms. So - according to his intention - you have to put it back in the right place.

To distinguish it, he called this technology molecular nanotechnology in the early 1990s and wrote a book on it in 1991.

Concept of the Drexler technology

The MNT concept is essentially based on so-called mechanosynthesis , i.e. the targeted gripping and placing of atomic and molecular building blocks.

• Molecular-sized robots, called assemblers , who work on nano-assembly lines in tiny factories and assemble at high speed from individual atoms and molecules whatever is needed in terms of human needs: cars and steaks, human organs, houses, spaceships and computers or even bacteria-sized “soldiers” “That are invincible.

• Robots that are channeled into the bloodstream are supposed to destroy invaders such as viruses and bacilli and repair defective cells and organs. All of this is practically free because the assemblers reproduce themselves and material can be extracted from waste.

• A single assembler consists of about a million atoms and tens of thousands of moving parts, each made up of a few atoms. A complex machine that, instead of semi-finished products like today's industrial robots , picks up molecules that are delivered from a warehouse, grips them from the conveyor belt and assembles them, with the chemical bonds serving as adhesives. Like the nanocomputers , the assemblers are purely mechanical constructs, consisting of levers, motors , gears, etc.

• These nanofactories should be able to transform anything as long as it does not contradict physical or chemical laws. Nature is the model: all a tree needs is light, air, water and some mineral salts. It uses photosynthesis to obtain food from sunlight, uses molecular machines to convert carbon dioxide into oxygen and hydrocarbon compounds, it forms roots, trunks and branches, produces leaves and bears fruit. Nature itself is familiar with molecular machines : motors , pumps and drives that are used, for example, to move bacteria through water. And she also constructed a nano-sized computer: the genetic material, the genome . It controls the manufacture of something highly complex from the cell nucleus, which contains the program that determines what gender, what size, what eye color, etc. the finished “product” will be.

Status of implementation of the vision

In recent years some of Drexler's assumptions have been confirmed experimentally and initial results have also been obtained.

• In 1998, Wilson Ho from Cornell University succeeded in assembling individual iron monocarbonyl molecules (FeCO) and iron dicarbonyl molecules (Fe (CO) ₂ ) from iron atoms (Fe) and carbon monoxide molecules (CO) using a scanning tunneling microscope .

• At the beginning of 2007, a research team from the Free University of Berlin, in collaboration with the CNRS in Toulouse, presented the first two nanowheels that can be rolled on a surface. They are triptycene molecules that resemble wheels with three spokes. They are connected by an axis made up of four carbon atoms. The rolling motion of the wheels is induced with the tip of a scanning tunneling microscope (STM) and read out simultaneously in real time. The corrugation of the surface plays an important role here: If this is too low, i.e. the surface is too flat, only a jumping of the molecules can be induced. It could also be shown that the path lengths of the wheels when rolling or jumping on the surface are characteristic of both mechanisms.

• Based on the same principle, this research collaboration has also developed nano gears, which, also driven by an STM tip, rotate along a jagged edge made of atoms.

• However, the two experiments also reveal a major difficulty that molecular machine builders face. The conventional mechanics, which are based on smooth surfaces, for example, can no longer be used without further ado. Individual surface atoms act like bumps. Every nanomachine (or molecular machine ) also needs external energy to move.

• Nature has elegantly solved this problem by chemically transferring the energy inside cells. They deliver ATP molecules in the form of electrons that are transferred to motor proteins. These can then trigger various biological processes, from the transport of individual chemical building blocks through the cell to muscle contraction on a large scale. For this reason, attempts are also being made to test the possibilities offered by the DNA molecule as a carrier of genetic information as a building material. For nanorobotics , it is crucial to be able to insert controllable elements at certain points in a grid.

• If you wanted to move macromolecules past each other in a vacuum or in air at a distance of less than a few atomic diameters , then they would stick to each other due to the Van der Waals forces . But if the macromolecules in water or in another suitable liquid embedding, then the fluid takes over the Van der Waals force, and can be the macromolecules friction past each move. This is how living cells work , and the scourge drive of the bacteria reaches 50 revolutions per second.

• Holding or letting go of individual atoms or molecules purely mechanically is also made more difficult by the Van der Waals forces, which has been referred to as the "sticky finger problem". This problem, and also the purely mechanical production of atomic bonds , was overcome by applying an electrical voltage , which was shown here.

• Many scientists are skeptical and consider the realization of Drexler's vision to be unrealistic. In the opinion of the proponents of the MNT, their opponents have so far not been able to come up with conclusive scientific arguments against the feasibility of MNT. It is undisputed that Drexler does not claim anything that contradicts the laws of physics or chemistry, because the practical proof is ultimately provided by nature today.

Web links

• General information on nanotechnology
• Foresight Institute (English)
• Die Zeit: Farewell to nanovision

Individual evidence

1. ↑ An Application of Mechanochemistry : Charles Day: Creating and Characterizing Individual Molecular Bonds with a Scanning Tunneling Microscope. In: Physics Today On The Web. Retrieved May 14, 2010 . 
2. ↑ Leonhard Grill et al. : Rolling a single molecular wheel at the atomic scale . In: Nature Nanotechnology . tape 2 , 2007, p. 95 , doi : 10.1038 / nnano.2006.210 (English, fhi-berlin.mpg.de ( Memento from July 13, 2011 in the Internet Archive ) [PDF]). Rolling a single molecular wheel at the atomic scale ( Memento of the original from July 13, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
3. ↑ An Application of Mechanochemistry : Charles Day: Creating and Characterizing Individual Molecular Bonds with a Scanning Tunneling Microscope. In: Physics Today On The Web. Retrieved May 14, 2010 .