What is Self-assembly?
Self-assembly is the autonomous organization of components into patterns or structures as a result of specific, local interactions among the components (without human intervention). Self-assembling processes are common throughout nature and technology. When the constitutive components are molecules, the process is termed molecular self-assembly.
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Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology.
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Self-organization in micron-sized Nb3O7(OH) cubes during a hydrothermal treatment at 200 °C. Initially amorphous cubes gradually transform into ordered 3D meshes of crystalline nanowires.[link]
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Note that self-assembly and self-organization are different. In self-assembling systems, individual parts move towards a final state, wheras in self-organizing systems, components move between multiple states, oscillate and may never come to rest in a final configuration. This makes self-organization much more complex to understand and duplicate. Self-assembly has become a rapidly growing science in past two decades for two reasons.
1) Self-assembly provides a major solution to the fabrication of ordered structures from nanometers to micrometers components but in principle, it is applicable at all scales. Interestingly these size fall between the sizes that can be manipulated by I) chemistry and those that can be manipulated by II) conventional manufacturing. Therefore it became a powerful tool in the window that was not touched intensively in past.
2) Self-assembly is a concept that is crucial to understand many structures important in various fundamental sciences including chemistry, biology and physics. In general, the stability of covalent bonds enables the synthesis of almost arbitrary configurations of up to 1000 atoms. Larger molecules, molecular aggregates, and forms of organized matter more extensive than molecules cannot be efficiently synthesized bond after bond. Therefore self-assembly is a powerful strategy for organizing matter larger than a molecule.
Self-assembly has introduced hope in industry too. It allows fabrication of smaller systems with better performance and facilitate the transition of current microelectronic to futuristic nanoelectronics (nanofabrication of smaller transistor or self-assembly of nanolitz wire). Self-assembly could play an important role in many other industries including pharmacudical and petrochemical sunthesis and manufacturing.
Although there are few studies about self-assembly of low aspect ratio filamentous materials including nanorods however no study on self-assembly of high aspect ratio filamentous material are conducted. This is important because high aspect ratio self-assembly in nature play very broad role from movement of cells with microtubules to transferring and storing information which happens in DNA. In general, self-assembly of high aspect ratio filamentous materials are more complicated than the low aspect ratio filamentous ones since the high aspect term convert self-assembly from a static system to a dynamic one simply because the filamentous materials can crawl on each other or make unparalleled initial bonds with many different energy state. Indeed, it can be considered as a self-organization instead of self-assembly.
1) Self-assembly provides a major solution to the fabrication of ordered structures from nanometers to micrometers components but in principle, it is applicable at all scales. Interestingly these size fall between the sizes that can be manipulated by I) chemistry and those that can be manipulated by II) conventional manufacturing. Therefore it became a powerful tool in the window that was not touched intensively in past.
2) Self-assembly is a concept that is crucial to understand many structures important in various fundamental sciences including chemistry, biology and physics. In general, the stability of covalent bonds enables the synthesis of almost arbitrary configurations of up to 1000 atoms. Larger molecules, molecular aggregates, and forms of organized matter more extensive than molecules cannot be efficiently synthesized bond after bond. Therefore self-assembly is a powerful strategy for organizing matter larger than a molecule.
Self-assembly has introduced hope in industry too. It allows fabrication of smaller systems with better performance and facilitate the transition of current microelectronic to futuristic nanoelectronics (nanofabrication of smaller transistor or self-assembly of nanolitz wire). Self-assembly could play an important role in many other industries including pharmacudical and petrochemical sunthesis and manufacturing.
Although there are few studies about self-assembly of low aspect ratio filamentous materials including nanorods however no study on self-assembly of high aspect ratio filamentous material are conducted. This is important because high aspect ratio self-assembly in nature play very broad role from movement of cells with microtubules to transferring and storing information which happens in DNA. In general, self-assembly of high aspect ratio filamentous materials are more complicated than the low aspect ratio filamentous ones since the high aspect term convert self-assembly from a static system to a dynamic one simply because the filamentous materials can crawl on each other or make unparalleled initial bonds with many different energy state. Indeed, it can be considered as a self-organization instead of self-assembly.
What is Nano-assembly?
Nanoassembly is the synthesis of a nanomaterial by assembly of its previously prepared nano-building-blocks (nanoparticles, or even molecules or atoms) which is a "bottom-up" approach. There are number of nanoassembly techniques currently investigated. For example;
1- Nanoscopic particles can be created in gas phase (by evaporation of a material and clustering of atoms and molecules in the gas phase) and then assembled together by a condensation, nucleation process, using possibly another material (surfactant) to prevent merging (agglomeration, coalescence) of clusters. Careful monitoring of thermodynamical parameters during this process can result in nanostructured materials with varying properties. Image link
1- Nanoscopic particles can be created in gas phase (by evaporation of a material and clustering of atoms and molecules in the gas phase) and then assembled together by a condensation, nucleation process, using possibly another material (surfactant) to prevent merging (agglomeration, coalescence) of clusters. Careful monitoring of thermodynamical parameters during this process can result in nanostructured materials with varying properties. Image link
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2- Virus Self-Assembly. Viruses are essentially mobile DNA containers that implicate themselves into living cells by usurping the cell's reproductive machinery to reproduce their own DNA. Viral DNA is housed in protective nano-scale containers, called capsids, that self-assemble within the host cell. These resilient proteinaceous packets self-assemble in response to a variety of weak forces that, in concert, provide the capsid with a great deal of stability. The weak forces at work include attraction or repulsion between electrostatic charges, water solubility, and constituent amino acid structures in various parts of the capsid.
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3- Self-Assembly of Lithographically Patterned 3D Micro/Nanostructures.The Gracias Lab at The Johns Hopkins University has developed a relatively easy, precise, and cost-effective process by which the 2D templates of semi-tethered "faces" can self-assemble into controlled 3D structures by utilizing the natural phenomena of surface tension as well as thin-film stress.
Some futurists (Drexler) propose nanoscopic 'assemblers' (nanobots) which would compose a nanoscopic particle or another nanobot on a molecule-by-molecule basis. This is, of course, only speculative fiction concerning the present state of science and technology. It is also questionable whether the science we know about allows for such nanomachines (Maxwell demons). Nevertheless, the operation of atomic force microscope in assembling artificial structures such as corals can be considered as a rather primitive example of this fiction. |
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