New Materials: Nanomaterials
Much of nanoscience and many nanotechnologies are concerned with producing new or enhanced materials.
Top-down and bottom-up
Nanomaterials can be constructed by top down techniques, producing very small structures from larger pieces of material, for example by etching to create circuits on the surface of a silicon microchip.
They may also be constructed by bottom up techniques, atom by atom or molecule by molecule. One way of doing this is self-assembly, in which the atoms or molecules arrange themselves into a structure due to their natural properties. Crystals grown for the semiconductor industry provide an example of self assembly, as does chemical synthesis of large molecules.
A second way is to use tools to move each atom or molecule individually. Although this ‘positional assembly’ offers greater control over construction, it is currently very laborious and not suitable for industrial applications.
The importance of scanning probe techniques
It has been 25 years since the scanning tunneling microscope
(STM) was invented, followed four years later by the atomic force microscope, and that's when nanoscience and nanotechnology really started to take off. Various forms of scanning probe microscopes based on these discoveries are essential for many areas of today's research. Scanning probe techniques have become the workhorse of nanoscience and nanotechnology research.
Here is a Scanning Electron Microscope (SEM) image of a gold tip for Near-field Scanning Optical Microscopy (SNOM) obtained by Focussed Ion Beam (FIB) milling. The small tip at the center of the structure measures some tens of nanometers.
Gold Tip for SNOM, imaged by SEM, 2006, Gian Carlo Gazzadi and Pietro Gucciardi, with Lucia Covi.(www.s3.infm.it/blowup) From Blow Up. Images from the nanoworld, edited by S3 Research Center (INFM-CNR), Damiani, Bologna. © S3 National Research Center (INFM-CNR), Modena, Italy
Current applications of nanoscale materials include very thin coatings used, for example, in electronics and active surfaces (for example, self-cleaning windows).
In most applications the nanoscale components will be fixed or embedded but in some, such as those used in cosmetics and in some pilot environmental remediation applications, free nanoparticles are used.
The ability to machine materials to very high precision and accuracy (better than 100nm) is leading to considerable benefits in a wide range of industrial sectors, for example in the production of components for the information and communication technology, automotive and aerospace industries.
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