Tremendous progress has been made over the past few years to control the aspects of fabricating simple nanostructures such as wires, tubes, spheres, cubes etc. However, in order to build functional nanodevices, for instance for nanoelectronics or nanobiotechnology, much more complex nanoarchitectures are needed. Initially, the most common, mostly top-down, fabrication methods used for this purpose have been based on nanolithographic techniques. Unfortunately, these methods are burdened with throughput restrictions and high cost and will be of limited use for commercial mass production of nanostructures. To overcome the limitations of nanolithography, a lot of attention has been focused on self-organized bottom-up approaches, which bear good prospects for large-scale fabrication of nanostructures with controlled morphology and dimensionality, and controlled synthesis of arrays. However, the fabrication of complex nanoarchitectures requires sophisticated transfer techniques, which are far from routine, time consuming, and with low reproducibility. To add to the arsenal of scaleable bottom-up fabrication processes, researchers in Germany have developed a method for the batch fabrication of 3D-nanostructures with tunable surface properties. Resembling suspended nanowire webs, these structures have a high potential for catalytic, sensing, or fluidic applications where a high surface to volume ratio is required.
People involved in designing and developing biosensing applications have high hopes that their field can benefit from nanotechnology. The term biosensing relates to systems that include electronic, photonic, biologic, chemical and mechanical means for producing signals that can be used for the identification, monitoring or control of biological phenomena. The resulting biosensors are devices that employ biological components such as proteins to provide selectivity and/or amplification for the detection of biochemical materials for use in medical diagnostics, environmental analysis or chemical and biological warfare agent detection. Applying nanotechnology to biosensors opens up novel detection possibilities thanks to the nano-physical properties of certain materials. A lot of research worldwide is devoted to developing nanobiosensors. A group in Switzerland, for example, is working on the development of two different kinds of label-free biosensors. One is a nanowire array, the other an optical biosensor based on localized surface plasmon resonance.
Most of today's rocket engines rely on chemical propulsion. All current spacecraft use some form of chemical rocket for launch and most use them for attitude control as well (the control of the angular position and rotation of the spacecraft, either relative to the object that it is orbiting, or relative to the celestial sphere). Real rocket scientists though are actively researching new forms of space propulsion systems. One heavily researched area is electric propulsion (EP) that includes field emission electric propulsion (FEEP), colloid thrusters and other versions of field emission thrusters (FETs). EP systems significantly reduce the required propellant mass compared to conventional chemical rockets, allowing to increase the payload capacity or decrease the launch mass. EP has been successfully demonstrated as primary propulsion systems for NASA's Deep Space 1, Japan's HAYABUSA, and ESA's SMART11 missions. A new EP concept proposes to utilize electrostatically charged and accelerated nanoparticles as propellant. Millions of micron-sized nanoparticle thrusters would fit on one square centimeter, allowing the fabrication of highly scaleable thruster arrays.
Biosensors, which incorporate biological probes coupled to a transducer, have been developed during the last two decades for environmental, industrial, and biomedical diagnostics. The application of nanotechnology to biosensor design and fabrication promises to revolutionize diagnostics and therapy at the molecular and cellular level. The convergence of nanotechnology, biology, and photonics opens the possibility of detecting and manipulating atoms and molecules using a new class of fiberoptic biosensing and imaging nanodevices. These nanoprobes and nanosensors have the potential for a wide variety of medical uses at the cellular level. The potential for monitoring in vivo biological processes within single living cells, e.g. the capacity to sense individual chemical species in specific locations within a cell, will greatly improve our understanding of cellular function, thereby revolutionizing cell biology. Existing nanoprobes have already demonstrated the capability of performing biologically relevant measurements inside single living cells.
The market for medical implant devices in the U.S. alone is estimated to be $23 billion per year and it is expected to grow by about 10% annually for the next few years. Implantable cardioverter defibrillators, cardiac resynchronization therapy devices, pacemakers, tissue and spinal orthopedic implants, hip replacements, phakic intraocular lenses and cosmetic implants will be among the top sellers. Current medical implants, such as orthopaedic implants and heart valves, are made of titanium and stainless steel alloys, primarily because they are biocompatible. Unfortunately, in many cases these metal alloys with a life time of 10-15 years may wear out within the lifetime of the patient. They also might not achieve the same fit and stability as the original tissue, and in a worst case, the host organism might reject the implant altogether. While available implants can alleviate excruciating pain and allow patients to live more active lives, there often are problems getting bone to attach to the metal devices. Small gaps between natural bone and the implant can increase over time, requiring the need for additional surgery to replace the implant. In the quest to make bone, joint and tooth implants almost as good as nature's own version, scientists are turning to nanotechnology. Researchers have found that the response of host organisms (including at the protein and cellular level) to nanomaterials is different than that observed to conventional materials. While this new field of nanomedical implants is in its very early stage, it holds the promise of novel and improved implant materials.
Nanocrystals, also called quantum dots (QD), are artificial nanostructures that can possess many varied properties, depending on their material and shape. For instance, due to their particular electronic properties they can be used as active materials in single-electron transistors. Because certain biological molecules are capable of molecular recognition and self-assembly, nanocrystals could also become an important building block for self-assembled functional nanodevices. The atom-like energy states of QDs furthermore contribute to special optical properties, such as a particle-size dependent wavelength of fluorescence; an effect which is used in fabricating optical probes for biological and medical imaging. So far, the use in bioanalytics and biolabeling has found the widest range of applications for colloidal QDs. Though the first generation of quantum dots already pointed out their potential, it took a lot of effort to improve basic properties, in particular colloidal stability in salt-containing solution. Initially, quantum dots have been used in very artificial environments, and these particles would have simply precipitated in 'real' samples, such as blood. These problems have been solved and QDs are ready for their first real applications.
A few years ago it was discovered that the process of thermal inkjet printing can be applied to fabricate hard tissue scaffolds (such as bones) and, just recently, soft tissue with liquid biomaterials. Research is also underway to use inkjet printing for the fabrication of organic semiconductors, which, because of their low stability, will be targeted at one-time-only applications such as water purity testers. Compared to the research done with respect to organic materials, inkjet printing of inorganic materials for the formation of active devices is relatively rare. To date, only a handful of inorganic materials have been inkjet printed, primarily because of the difficulty in preparing inkjet-printable precursors. Current methods for the production of functional inorganic electronic devices are quite expensive because they require the sequential deposition, patterning, and etching of selected semiconducting, conducting, and insulating materials, involving multiple photolithography and vacuum-deposition processes. Now though, researchers have come up with a process for printable inorganic semiconductors, opening a route to the fabrication of high-performance and ultra low-cost electronics such as transparent electronics and thin film solar cells.