Civilization as we know it would, literally, fall apart without techniques to join materials together. With its historic development tracing back to the Bronze Age, welding has been one of the key technologies that serves modern industry in broad areas such as construction, manufacturing, and engineering. As we have reported in a previous Nanotechnology Spotlight, this Bronze Age technique could prove very useful in building complex nanostructures. Researchers at the University of Sheffield in the UK have now demonstrated the ability to reliably weld individual nanowires and nanoobjects into complex geometries with controllable junctions. This represents a significant breakthrough for the current and future bottom-up localized assembly, integration, and repair of micro- and nanodevices.
Stakeholders attending the second annual "Safety for Success" dialogue last October in Brussels agreed that while many activities had taken place during the past year towards the responsible development and regulation of nanotechnologies more effort was needed. Discussion highlighted three areas that require coordinated effort from all parties: 1) Developing trustworthy information on products containing nanomaterials that are on or near the market, and on how they are tested. 2) Meaningful public engagement on the basis of shared definitions of nanotechnology. 3) Ongoing regulatory reviews to provide clear guidance to industry on how to interpret regulatory frameworks, and clear indications to the public about action being taken in cases where relevant risk data is limited or uncertain. In addition, the meeting identified a number of key points that need to be addressed in order to meet these three priorities.
Olfaction, our sense of smell, depends on the capability of specialized sensory cells in the nose to detect airborne odorant molecules. These olfactory cells contain specific protein molecules that acts as 'olfactory receptors' - they bind only to specific odorant molecules present in the air inhaled through the nose. When such a binding event occurs, the olfactory receptors change their shape and this deformation triggers chemical and electrical signals which are eventually transmitted to the brain through neurons. So, in a nutshell, this is how we smell. Human and especially some animal noses (think bomb-sniffing dogs) are very sophisticated and extremely sensitive gas sensors that can distinguish between very similar gas molecules. Researchers have been trying for a while to replicate the human olfactory sense - a concept called electronic nose (e-nose). While most nanotechnology-based efforts have focused on nanowires, new research conducted in Korea has demonstrated the detection of specific odorant molecules with a single-carbon-atomic resolution using a human olfactory receptor-functionalized carbon nanotube based sensor.
One of the issues in using carbon nanotubes for applications is the challenge of separating metallic from semiconducting single-walled carbon nanotubes (SWCNT) after production. Developing a rapid and parallel technique for the electronic characterization of high-density arrays of SWCNT devices is essential for future large-scale production processes of nanoelectronics components. Currently used methods for electronic characterization of SWCNT devices and arrays are time consuming to set up, slow to execute, and not suitable for large-scale deployment. These methods include direct electron transport measurements and scanning probe microscopy, which can map the surface potential along a nanotube; again, a very slow technique with limited ability to be integrated into the process flow for microelectronic fabrication and characterization. More recent demonstrations of sorting nanotubes with DNA have been more promising but are very early stage. Researchers in Germany have now presented Voltage-Contrast Scanning Electron Microscopy (VC-SEM) as a new technique for the characterization of molecular electronic devices and device arrays.
The emerging field of transparent and flexible electronics not only holds the promise of a new class of device components that would be more environmentally benign than current electronics; being able to print transparent circuits on low-cost and flexible plastic substrates also opens up the possibility of a wide range of new applications, ranging from windshield displays and flexible solar cells to clear toys and artificial skins and even sensor implants. Three broad application areas for this technology are taking shape: transparent displays; flexible displays; and transparent/flexible electronics. Traditional materials used for transparent electronics include indium tin oxide films and indium oxide nanowires. In their search for materials that can offer even higher mobility and therefore even better performance, researchers have turned to single-walled carbon nanotubes .New work at the University of Southern California has now demonstrated the great potential of massively aligned single-walled carbon nanotubes for high-performance transparent electronics.
The flurry of recent announcements regarding reports, international cooperations, and new research activities that deal with the potential risks of manufactured nanomaterials is a clear indication that the field of nanotoxicology is gaining momentum - and not too soon. While there still is no coherent international approach to determining if and what risks are posed by what kind of nanotechnology materials, individual research groups are picking certain areas of concern and forge ahead with - often highly specific - toxicology studies. A lack of standards and definitions makes these early investigations hard to compare and sometimes they even contradict each other, a situation that is especially confusing in risk assessments of carbon nanotubes. Some studies, though, present findings that, on the face of it, are especially worrying in their potential implications and deserve much more attention to be sorted out one way or another. A recent report on the toxicity of metal nanoparticles in soil is such an example.
Graphene is a recently discovered allotrope of carbon, which consists of a planar single sheet of carbon atoms arranged in honeycomb lattice. It has attracted tremendous attention of the nanotechnology research community owing to a number of unique physical properties. From a practical point of view, some of the most interesting characteristics of graphene are its extraordinarily high room temperature carrier mobility and recently measured extremely high thermal conductivity. The outstanding current and heat conduction properties of graphene are beneficial for the proposed electronic, interconnect, and thermal management applications. There is a realistic possibility that soon the fastest transistors and most sensitive detectors will be made out of graphene. For instance, we have just reported that next generation computer memory could be made of graphene. In order to build useful devices from materials which have only atomic thickness, one has to use extensively scanning electron microscopy, transmission electron microscopy, and focused ion beam processing. Unfortunately, all material characterization techniques which involve electron beam irradiation of the samples may result in damage to the material and disordering of the crystalline lattice. So far, despite the practical importance of the issue, the scale of this potential damage to single-layer of bi-layer graphene has not been investigated. What happens with the crystalline lattice has also been unclear.
Neural engineering is an emerging discipline that uses engineering techniques to investigate the function and manipulate the behavior of the central or peripheral nervous systems. Neural engineering is highly interdisciplinary and relies on expertise from computational neuroscience, experimental neuroscience, clinical neurology, electrical engineering and signal processing of living neural tissue, and encompasses elements from robotics, computer engineering, neural tissue engineering, materials science, and nanotechnology. In order for neural prostheses to augment or restore damaged or lost functions of the nervous system they need to be able to perform two main functions: stimulate the nervous system and record its activity. To do that, neural engineers have to gain a full understanding of the fundamental mechanisms and subtleties of cell-to-cell signaling via synaptic transmission, and then develop the technologies to replicate these mechanisms with artificial devices and interface them to the neural system at the cellular level. A group of European researchers has now shown that carbon nanotubes may become the ideal material for repairing damaged brain tissue.