Nanoallotropes, or allotropes of nanomaterials, are nanoporous materials that have the same chemical composition (e.g., Au), but differ in their architecture at the nanoscale (that is, on a scale 10 to 100 times the dimensions of individual atoms).
These differences in the growth rates are translated into a progressive development of a subparticle structure at the nanoscale.
In many materials, atoms or molecules agglomerate together to form objects at the nanoscale.
In describing nanostructures it is necessary to differentiate between the number of dimensions on the nanoscale.
Nanotextured surfaces have one dimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have two dimensions on the nanoscale, i.e., the diameter of the tube is between 0.1 and 100 nm; its length could be much greater.
Finally, spherical nanoparticles have three dimensions on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension.
Materials which atoms and molecules form constituents in the nanoscale (i.e., they form nanostructure) are called nanomaterials.
Materials with structure at the nanoscale often have unique optical, electronic, or mechanical properties.
While there are sensory advantages present at the macroscale compared to the limited sensorium available at the nanoscale, proposals for positionally controlled nanoscale mechanosynthetic fabrication systems employ dead reckoning of tooltips combined with reliable reaction sequence design to ensure reliable results, hence a limited sensorium is no handicap;
However, the concept of suppressing mutation raises the question: How can design evolution occur at the nanoscale without a process of random mutation and deterministic selection? Critics argue that MNT advocates have not provided a substitute for such a process of evolution in this nanoscale arena where conventional sensory-based selection processes are lacking.
The limits of the sensorium available at the nanoscale could make it difficult or impossible to winnow successes from failures.
In this book he describes radical nanotechnology (as advocated by Drexler) as a deterministic/mechanistic idea of nano engineered machines that does not take into account the nanoscale challenges such as wetness, stickiness, Brownian motion, and high viscosity.
For the future, some means have to be found for MNT design evolution at the nanoscale which mimics the process of biological evolution at the molecular scale.
A handicap in this process is the difficulty of seeing and manipulation at the nanoscale compared to the macroscale which makes deterministic selection of successful trials difficult;
Although this appears a challenging problem given current resources, many tools will be available to help future researchers: Moore's law predicts further increases in computer power, semiconductor fabrication techniques continue to approach the nanoscale, and researchers grow ever more skilled at using proteins, ribosomes and DNA to perform novel chemistry.
They merge at the nanoscale into nanoelectromechanical systems (NEMS) and nanotechnology.
The associated research and applications are equally diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the nanoscale to direct control of matter on the atomic scale.
Governments moved to promote and fund research into nanotechnology, such as in the U.S. with the National Nanotechnology Initiative, which formalized a size-based definition of nanotechnology and established funding for research on the nanoscale, and in Europe via the European Framework Programmes for Research and Technological Development.
Materials reduced to the nanoscale can show different properties compared to what they exhibit on a macroscale, enabling unique applications.
Much of the fascination with nanotechnology stems from these quantum and surface phenomena that matter exhibits at the nanoscale.