纳米科学与技术简介？ Introductionto nanoscience and nanotechnology Kannan M. Krishnan's research group, University of Washington, WA, USA The basic concept of nanometer, nanoscience andnanotechnology are introduced at first. Then further understanding of nanotechnologyis given by describing the existing nanotechnologies, the reasons to developnanotechnology now and the major challenges we face. Some social issues andfuture prospects of nanoscience and nanotechnology are mentioned in the end. A nanometer isone billionth of a meter (10-9), which is roughly four times thediameter of an individual atom. For comparison, a typical nanometer-scalefeature size of about 10 nanometers is 1,000 times smaller than the diameter ofa human hair.1 This length scale is quite important for thedevelopment of science and technology because of the wave-like properties ofelectrons inside matter. Without changing the material’s chemical composition,we may control fundamental properties of materials like their meltingtemperatures, magnetic properties, charge capacities, and even their colors bynanofabrication.1 Currently there are a lot ofdifferent opinions about what exactly nanotechnology is. In general, nanotechnology can be understood as atechnology of the design, fabrication and applications of nanostructures andnanomaterials. Nanotechnology also includes a fundamental understanding ofphysical properties and phenomena of nanomaterials and nanostructures. The studyof fundamental relationships between physical properties and phenomena andmaterial dimensions in the nanometer scale isalso referred to as nanoscience. Actually, nanotechnology is not totally a new concept. Many existingtechnologies do already depend on nanoscale processes. Photography andcatalysis are two examples of “old” nanotechnologies that were developed bypractice in an earlier period despite their developers’ limited abilities toprobe and control matter at a nanoscale. For many of the existing technologiesutilizing nanometer-scale objects, the role that the nanometer scale played wasnot even appreciated until recently. For example1, we know now thatadding certain inorganic clays to rubber dramatically improves the lifetime andwear properties of tires because the nanometer-sized clay particles bind to theends of the polymer molecules, which are “molecular strings” and prevent themfrom unraveling. Why do we emphasize so much about nanoscience and nanotechnologynow? Of course, the industrial need to make nanomaterials is a main reason.However, nanoscience has exploded in the last decade, primarily as the resultof the development of new tools that have made the characterization andmanipulation of nanostructures practical, and also as a result of new methodsfor the preparation of these structures. First of all, as the transdisciplinary science and technologydevelop fast, an industrial need shows up to exploit the phenomena andproperties of materials at the nanometer length scale. This is because thereare ultimate limits of miniaturization in different fields of industry such assilicon-based technology, including memory and logic applications. Another driving force for usto research nanoscience and nanotechnology now is the demand ofpharmaceuticals, healthcare, and life sciences. In fact, cells in animals’bodies are an example of nanotechnology in nature, and they can be changed ifwe are able to manipulate at nanometer length scale. Nanotechnology will allowus to place components and assemblies inside cells. The potential applicationsinclude new nanostructured drugs, gene and drug delivery systems targeted tospecific sites in the body, biocompatible replacements for body parts andfluids, self-diagnostics for use in the home, sensors for labs-on-a-chip, andmaterial for bone and tissue regeneration. Nowadays, we have some novel tools to measure and characterizenanomaterials and nanostructures. Scanning probe microscopies haverevolutionized the characterization of nanostructures, and the development ofnew variants of scanning probe devices continues apace. Older tools, especiallyelectron microscopy, continue to play essential roles. In biologicalnanoscience, the combination of X-ray crystallography and NMR spectroscopyoffers atomic resolution structural information about structures as complex asentire virus particles.2 At the same time, the new technical advances also make it possibleto fabricate at the nanometer-scale. The ability to fabricate and processnanostructures and nanomaterials is the first corner stone in nanotechnology.Obviously, there are two approaches to the synthesis of nanomaterials and thefabrication of nanostructures: top-down and bottom-up. Attrition (A rubbingaway or wearing down by friction) is a typical top-down method in makingnanoparticles, whereas the colloidal dispersion (A substance with components ofone or two phases, a type of mixture intermediate between a solution and aheterogeneous mixture with properties also intermediate between the two) is agood example of bottom-up approach in the synthesis of nanoparticles.3 Although the research on nanotechnology is based on establishedfundamentals and technologies such as physics, chemistry, materials science anddevice science and technology, researchers in the field face many newchallenges that are unique to nanostructures and nanomaterials.4 First of all, the building and demonstration of novel tools to studyat the nanometer level what is being manifested at the macro level is a greatchallenge. The small size and complexity of nanoscale structures make thedevelopment of new measurement technologies more challenging than ever.Measurements of physical properties of nanomaterials require extremelysensitive instrumentation, while the noise level must be kept very low. That isbecause the noise which is one kind of vibration could influence the results ofmeasurements.5 Also, other challenges arise in the nanometer scale, but are notfound in the macro level. For example, random doping (the process of addingimpurity additions into intrinsic semiconductors) fluctuations become extremelyimportant at the nanometer scale, since the fluctuation of the dopingconcentration would not be tolerable at the nanometer scale. For the fabrication and processing of nanomaterials andnanostructures, the challenges include: (1) Overcoming the huge surface energy,a result of large surface to volume ratio. (2) Ensuring that all nanomaterialswith desired size, uniform size distribution, morphology, crystallinity,chemical composition, and microstructure, that altogether result in desiredphysical properties. (3) Preventing nanomaterials and nanostructures fromcoarsening through agglomeration as time evolves.5 Even though the challenges mentioned above have already beenconquered, developing techniques for fabricating nanostructures inexpensivelyin very large numbers—that is, manufacturing them—is still an area thatrequires substantial effort: nanoscience will not be fully successful until ithas provided the base for manufacturing technologies that are economicallyviable. There are some other issues about nanotechnology. For instance, towork in nanoscience, it is a prerequisite to be able to fabricate andcharacterize nanostructures. Certain instruments, especially electronmicroscopes, are sufficiently expensive that they should be operated withinconsortia; others, especially state-of-the-art scanning probe devices, shouldbe distributed to qualifying individual research groups. For the more expensivefacilities—for example, high-resolution e-beam writers, good clean-roomfacilities, and mask-making facilities—a substantial, early investment isneeded to prevent fabrication delays. Nanoscience is one of the unexplored frontiers of science. It offersone of the most exciting prospects for technological innovation. And if itlives up to its promise as a generator of technology, it will be at the centerof fierce international competition. However, challenges and the potential riskof environmental impact still exist in the way of future development ofnanotechnology and nanoscience, which demand further progressive investigation and properoverall evaluation.6 References: ­­­­1­­­ .Alivisatos, M.C. Roco, R.S. Williams, Introduction to nanotechnology fornonspecialists , NSF Report (XXV-XXX) ­­2G.Whitesides, P. Alivisatos, Fundamental scientific issues for nanotechnology. 1-16 3P. Ball, Made to measure. (Ch 2 p. 63-85) Princeton Press(1996) 4Gary Stix, Little big science. Scientific American, September32-37 (2001) 5G. Cao, Nanostructures and nanomaterials. Imperial CollegePress 7-11 (2004) 6 VickiL.Colvin, The potential environmental impact of engineered nanomaterials ,Nature Biotechnology, vol 21 Oct.2003 查看更多1个回答 . 1人已关注
第1天
关注盖德视界
添加小助手
