Micro-and/or nano-electromechanical systems (MEMS/NEMS) are the basis of future nanotechnology, because they combine miniature sensors and actuators with electronics. The selection of appropriate materials for MEMS/NEMS fabrication is based on the careful consideration of a material's properties with regard to its intended application. For example, many MEMS devices, such as pressure, chemical and bio sensors, rely on actuation of a membrane structure and require a high fracture toughness material for the enhanced durability and shock resistance. On the other hand, for fabrication of controlled nanostructures, the material should be machinable up to atomic level. Currently, the materials used for MEMS/NEMS fabrication are based on silicon or oxides, which are brittle and have size effects such as lattice defects, anisotropy, grains and grain boundaries. These effects are the limiting factors in the reduction of pattern size, especially when a dimension of the pattern approaches a few tenths of a nanometer. Researchers in Japan now have introduced zirconium-based glass thin films for the fabrication of 3D micro- and nanostructures. These materials exhibit excellent micro/nano-formability under very low stresses, and are expected to become one of the most useful materials for fabricating NEMS/MEMS devices.
There seem to be an increasing number of websites, articles and investment reports that push, some might say hype, nanotechnology stocks as the next stock market super growth area. On the other hand, some investors are wary of a nanotechnology boom, where too much money chases too few listed companies, turning into a dot.com-like bust. Hype usually involves a bit of underlying truth about a trend but says nothing about whether something is going to be a good investment. As the International Herald Tribune put it: "While nanotechnology is spurring a revolution in electronics and medicine, investors seeking to benefit may need a lot of luck, as they did during the Internet bubble of the 1990s." The current interest in nanotech stocks is driven by the many advances that nanoscience and nanotechnology promise. The commercial realization of most of these promises lies in the (some say near, some say distant) future; things like quantum computing, molecular electronics, or lab-on-a chip medicine. In its current state, nanotechnology to a large degree takes place in labs and there is only a trickle of products coming to the market. All of these products are incremental improvements of existing products - scratch-resistant paint, better engine oil, antimicrobial household products, smaller chips, improved cosmetics, etc. What we are seeing right now is the beginning of a large technological trend and a stock buyer has to understand the difference between the many promises of nano- technologies, the research taking place today, and the actual contribution of nanotechnologies to commercial products. Let's look at a few facts that might give some perspective on what investing in nanotechnology stocks today is about - how has the market performed so far? what exactly is a "nanotechnology stock"? and the issue with these trillion dollar market size forecasts.
The precise positioning of nanoparticles on surfaces is key to most nano- technology applications especially molecular electronics. However, for automated patterning of particles, existing methods are either slow (e.g., dip-pen lithography) or require prefabricated patterns (e.g., by electrostatic positioning or by successive self-assembly, transfer, and integration). Moreover, the sorting of differently sized particles, organelles, and cells in microfluidic networks is important for many biological and medical applications. Purely size-based sorting would offer the greatest control, but an automated method so far does not exist. Researchers in Switzerland now have discovered that acoustic streaming leads to sorting of particles dependent on their size. Nanoparticles aggregate at the antinodes and micrometer-sized particles aggregate on the nodes of oscillation patterns on micro- machined cantilevers. These surprising results open new possibilities for the sorting of nanoparticles.
Hyperthermia therapy, a form of cancer treatment with elevated temperature in the range of 41-45C, has been recently paid considerable attention because it is expected to significantly reduce clinical side effects compared to chemotherapy and radiotherapy and can be effectively used for killing localized or deeply seated cancer tumors. Accordingly, various forms of hyperthermia have been intensively developed for the past few decades to provide cancer clinics with more effective and advanced cancer therapy techniques. However, in spite of the enormous efforts, all the hyperthermia techniques introduced so far were found to be not effective for completely treating cancer tumors. The low heating temperature owing to the heat loss through a relatively big space gap formed between targeted cells and hyperthermia agents caused by the hard to control agent transport, as well as killing healthy cells attributed to the difficulties of cell differentiations by hyperthermia agents, are considered as the main responsibilities for the undesirable achievements. In a possible breakthrough, researchers in Singapore now report the very promising and successful self-heating temperature rising characteristics of NiFe2O4 nanoparticles. Different from conventional magnetic hyperthermia, in-vivo magnetic nanoparticle hyperthermia is expected to be one of the best solutions for killing tumor cells which are deeply seated and localized inside the human body.
Nanowires are expected to play an important role in the emerging fields of nanoelectronics and nanooptics. In particular, the permanently growing complexity of integrated circuit designs requires a further reduction of the size of IC components that nanowires could facilitate. Nanowires are also a possible candidate for future functional nanostructures in plasmonic devices, i.e. for information (light) propagation and manipulation below the optical diffraction limit. For these purposes, cobalt disilicide (CoSi2) is a very promising contact material due to its extremely useful properties such as low resistance, its metallic behavior, its low lattice mismatch to Si of only -1.2%. the plasmon wavelength of 1.2 micrometer, and its compatibility with modern silicon technology. Many efforts have been made to fabricate silicide nanowires employing the bottom-up approach without elaborate microlithography. Researchers in Germany now have demonstrated a promising technique that allows the defect-induced formation and placing of cobalt disilicide nanowires by focused ion beam synthesis in silicon directly where it is needed.
The discovery of numerous nanomaterials has added a new dimension to the rapid development of nanotechnology. Consequently, the professional and public exposure to nanomaterials is supposed to increase dramatically in the coming years. Especially, carbon-based nanomaterials (CBNs) are currently considered to be one of the key elements in nanotechnology. Their potential applications range from biomedicine through nanoelectronics to mechanical engineering. Thus, it is primordial to know the health hazards related to their exposure. As the public calls for safety studies get louder more and more researchers begin to study the potential toxicity of nanomaterials. Especially carbon-based nanomaterials, due to their numerous and wide-ranging applications and increasing real life usage, get nanotoxicological attention. Scientists in Switzerland studied the toxicity of carbon- based nanomaterials (nanotubes, nanofibers and nanowires) as a function of their aspect ratio and surface chemistry. Their work clearly indicates that these materials are toxic while the hazardous effect is size-dependent.
Silver has long been recognized for its infection-fighting properties and it has a long and intriguing history as an antibiotic in human health care. In ancient Greece and Rome, silver was used to fight infections and control spoilage. In the late 19th century, the botanist von Naegeli discovered that minute concentrations of silver contained microbiocidal properties. However, as the first antibiotics were discovered, this old household remedy was quickly forgotten. In an alarming trend, bacteria and other microorganisms that cause infections are becoming remarkably resilient and can develop ways to survive drugs meant to kill or weaken them. This antibiotic resistance is due largely to the increasing use of antibiotics. This led researchers to re-evaluate old antimicrobial substances such as silver. Silver nanoparticles have become the promising antimicrobial material in a variety of applications because they can damage bacterial cells by destroying the enzymes that transport cell nutrient and weakening the cell membrane or cell wall and cytoplasm. Unfortunately, in practical applications, the pure silver nanoparticles are unstable with respect to agglomeration. In most cases, this aggregation leads to the loss of the properties associated with the nanoscale of metallic particles. The stabilization of metallic colloids and thus the means to preserve their finely dispersed state is a crucial aspect to consider during their applications. Researchers in China have successfully demonstrated the use of a natural macroporous matrix for fabricating a stable, biocompatible nanocomposite with high silver content for antimicrobial purposes.
The ability to detect few or individual molecules in solution is at present largely limited to fluorescence techniques, and a comparable method using electrical detection has so far remained elusive. Such a technique would be highly desirable for lab-on-a-chip applications and when labeling with fluorophores is invasive or impossible. More importantly, it would pave the way for fluidic devices in which individual ions are electrically detected and manipulated, allowing a new class of fundamental experiments on nonequilibrium statistical physics, transport at the molecular scale, and a broad range of biophysical systems. Researchers in The Netherlands now have demonstrated a new nanofluidic device for the detection of electrochemical active molecules with an extremely high sensitivity. A prototype device allows detecting fluctuations due to Brownian motion of as few as approx. 70 molecules, a level heretofore unachieved in electrochemical sensors. Ultimately, the researchers hope the device will not only be able to detect single molecules in the device, but also discriminate between various species.