subject: Molecular Nanotechnology [print this page] Molecular Nanotechnology Molecular Nanotechnology
Nanotechnology is a still evolving technical approach. Applications of this field are beyond our imaginations. Molecular nanotechnology refers to the molecular engineered nanosystems which operate on nano scale in order to build complex structures. Principles of molecular assembly and quantum physics are mainly used in this branch of nanotechnology.
Before concerning about molecular nanotechnology we should clearly understand that molecular assembly' which specifically mentioned in molecular nanotechnology and self assembly' which is mentioned in basic nanotechnology are having their own characteristics, even though they operate in hand to hand.
Self assembly means, molecules arrange themselves in an organized manner, in order to give rise to a specific larger material structure. In these procedures voltage or electromagnetic waves can be used to signal the start point, end point, rate of assembly and assembling configuration of the self assembling process.
In molecular assembly molecules are assembled in to a specific configuration by a machine which is a biological or a chemical complex unit. This so called machine, known as the molecular assembler controls the entire assembling process. The signaling methods which involve in the self assembling mechanism: voltage and electromagnetic waves can be used to control the activity of the molecular assembler. As long as the molecular assembler is under control, molecular assembling can be manipulated by human.
Molecular assembler is a nano-scale-machine which has the ability to produce a desired structure in the atomic scale using principles of mechanosynthesis. This machine should have the ability to position atoms on other atoms in a desired angle and a desired distance producing a desired bond with desired strength. This is an advanced stage of nanotechnology which is very sophisticated. Construction of such molecular assembling device will require biological and chemical principles rather than conventional mechanical engineering approaches. However, the sophisticated mechanical functionality of the various parts of the molecular assembler should enable programmable, positional assembly to atomic specification.
Practically assembling a nano scale device to perform mechanical function is a very difficult operational act. Modern science is capable of manipulating molecules according to their chemical nature. Scientists even have methods to deal with the atomic nucleus in a desirable manner. But manipulating individual molecule is difficult. This remains as a one barrier on the way to mechanosynthesis of nano scale devices.
Biology has already shown that molecular machines which act according to biological and chemical principles are possible. Molecular levels of the biological systems are controlled by these molecular device systems. But they do not agree with some of the mechanical engineering principles. One good example for biological molecular machinery is the enzyme activity.
Enzymes which are biological catalysts are globular proteins with the ability of enhancing the rate of biological reactions. They perform their function by binding with the substrate molecules and changing their molecular configuration. Sometimes they develop bonds between molecules and sometimes they split molecules. Enzymes act only on specific molecules. Substrate specificity of enzymes is achieved by the shape and bond energy of the substrate binding site of the enzyme which is known as the active site. So only specific molecules with the matching shape and potential energy will bind to the enzyme and proceed with the reaction. Chemical and physical nature of the enzyme is not altered during the reaction. Therefore it remains in its initial status at the end of the reaction with the ability of catalyzing another reaction. By this mechanism a single enzyme molecule can participate in several molecular assemblies until its polypeptide chains start to change its normal arrangement thus the enzymes normal function. Enzymes demonstrate many basic properties of molecular assemblers.
Enzymes can act on molecular level and perform desired positional assembly of atoms.
It can form desired angles and desired distance between atoms in order to produce desired bonds.
Chemical and physical properties of enzyme are not getting altered during the molecular assembly.
Single enzyme molecule can perform several molecular formations.
Activity of enzymes can be controlled by chemical and electrical signals.
Even though biological molecular machine systems are evolved and successfully functioning, non-biological molecular machine systems are still in their primitive stages.
Several scientists are researching on development of non-biological molecular machines which will ultimately lead to the production of molecular assemblers which is the key feature of molecular nanotechnology. Dr. Alex Zettl and his colleagues at Lawrence Berkeley Laboratories and UC Berkeley have developed molecular devices, whose motion is controlled by changing voltage; a nanotube nanomotor, a molecular actuator and a nanoelectromechanical relaxation oscillator.
Some scientists have already performed positional molecular assemblies without using molecular assemblers. They have to use larger units that are external to the molecular environment to position molecules. Signals like voltage or electromagnetic waves, which are transmitted from those external units to the molecules, will control their positional assembly.
Problems arise while trying to assemble molecules at nano scale without a molecular assembler. For example, without a molecular assembler, in order to manipulate molecules, an external controlling unit is necessary. That external source will require space and specific conditions to function. But once molecular assemblers are produced they can perform numerous molecular assemblies according their program unless it is deactivated. The molecular complexity level that an external unit can handle in molecular positioning is limited. They would not be able to handle high complex molecules, because their signals will simply disturb the atoms in the molecules before starting the desired molecular assembly.
There are number of applications of molecular nanotechnology. One major application is the nano-medicine. Molecular assemblers can be used to heal internal damages without time consuming, risk taking surgeries. Implanted molecular assemblers can synthesis various essential substances, required for normal function of living beings, but absent inside the body due to various disorders in the synthetic pathways. Molecular machine systems can act on foreign materials inside the body and destroy them when needed. They can also destroy overgrowths like cancers. Some patients need to take some medicine continuously. Molecular assemblers can synthesis those chemical compounds in vivo, utilizing atoms existing inside the living beings. Another application of molecular nanotechnology is the self repairing mechanisms. Damages to various macroscopic structures can be repaired by the action of molecular assemblers.
Most of the things related to molecular nanotechnology are still hypothetical. But with the development of nanotechnology, this field will also mature and humans will be able to do many things at molecular level, which are beyond the modern scientific principles.
