Nanotechnology's much-touted notion of bottom-up fabrication - the key concept behind every idea and model of advanced nanotechnologies - so far doesn't have much to do with assembly-line style of manufacturing; rather, it relies on natural self-assembly processes. The stability of covalent bonds enables the chemical synthesis of almost arbitrary configurations of up to 1000 atoms. Larger molecules, molecular aggregates, and forms of organized matter more extensive than molecules cannot be synthesized bond-by-bond. Self-assembly is one strategy for organizing matter on these larger scales. Nevertheless, as a wholly novel way to manufacture and create new materials, self-assembly is of fundamental importance for the future of a myriad of technologies. While there is no doubt self-assembly works, as evidenced by the world around us, scientists have just begun to understand and devise working examples of self-assembly. Much of this work has been at the millimeter and micron scales were it is relatively easy to fabricate components for assembly. A recent paper details a general method, using microcontact printing, for modifying cubic building blocks with nanoscale dimensions. The controlled assembly of metallic nanoparticles remains a challenge and this work provides a novel functional example to study and build upon.
Regenerative medicine is an area in which stem cells hold great promise for overcoming the challenge of limited cell sources for tissue repair. Stem cell research is being pursued in laboratories all over the world in the hope of achieving major medical breakthroughs. Scientists are striving to create therapies that rebuild or replace damaged cells with tissues grown from stem cells and offer hope to people suffering from cancer, diabetes, cardiovascular disease, spinal-cord injuries, and many other disorders. Embryonic stem cells are pluripotent. That means that during normal embryogenesis human embryonic stem cells (hESCs) can differentiate into any of the more than 220 cell types in the adult body. Researchers have now developed a new methodology to enhance the vascular differentiation of hESCs by incorporating growth factor-releasing micro- and nanoparticles in embryoid bodies.
Nanomaterial-based drug-delivery and nanotoxicology are two of the areas that require sophisticated methods and techniques for characterizing, testing and imaging nanoparticulate matter inside the body. Especially the potential risk factors of certain nanomaterials have become a heated topic of discussion recently. Most, if not all, toxicological studies on nanoparticles rely on current methods, practices and terminology as gained and applied in the analysis of micro- and ultrafine particles and mineral fibers. The development of novel imaging techniques that can visualize local populations of nanoparticles at nanometer resolution within the structures of cells - without destroying or damaging the cell - are therefore important. Researchers in the U.S. have now demonstrated that at ultrasonic frequencies, intracellular nanomaterial cause sufficient wave scattering that a probe outside the cell can respond to. This ultrasonic holography technique provides a non-invasive way of looking inside a cell.
A fast-growing body of nanotechnology research is dedicated to nanoscale motors and molecular machinery. The results of these studies are spectacular: well-designed molecules or supramolecules show various movements upon exposure to various stimuli, such as molecular shuttles, molecular elevators and molecular motors. So far, however, nobody has been able to directly observe the movements of these molecular machines and utilize the mechanical work done by them. Now, an international group of researchers have succeeded in amplifying the minuscule change in structures at a molecular level caused by an external stimulus (light) to a macroscopic change through a cooperative effect of liquid crystals. Using liquid-crystalline elastomers (LCEs) ? unique materials having both properties of liquid crystals (LCs) and elastomers ? the scientists have successfully developed new photomechanical devices, including the first light-driven plastic motor. In other words, with this novel material the energy from light can be directly converted into mechanical work without the aid of batteries, electric wires, or gears.
One of the true nanotechnologies that pre-dates the explosion of the popular use of the word during the past few years is Atomic Layer Deposition (ALD). This gas phase chemical process is used to create extremely thin coatings only a few nanometers thick which can be deposited in a precisely controlled way. Initially used as a technique for making a specific type of light display (electroluminescent display) smaller and more efficient, the ALD process was invented and patented by Tuomo Suntola and his co-workers in Finland in 1974 (co-incidentally, this is the year that the term 'nanotechnology' was first defined by Norio Taniguchi). The fundamental notion behind Atomic Layer Deposition is rather simple: It is a process by which an atomic layer of material can be affixed to a surface material one layer at a time. By depositing one layer per cycle, ALD offers extreme precision in ultra-thin film growth since the number of cycles determines the number of atomic layers and therefore the precise thickness of deposited film.
Storing the fuel that is needed to run a hydrogen car in a compact and affordable way is still a major challenge. You would need about 5 kg of hydrogen to have the same average driving range as today's cars. Since hydrogen's density is only 1/10th of a gram per liter at room temperature, that means you somehow need to pack 50,000 liters of hydrogen into your tank. There are three ways of doing this: as a high-pressure compressed gas; a cryogenic liquid; or as a solid. Rather than using hundreds of atmospheres to compress hydrogen into a tank, or cooling it down to minus 252 C to liquefy it, hydrogen storage in solid form offers the safest alternative for transportation and storage of hydrogen. Research in this area has led to metal hydrides, chemical hydrides, and physisorption-based storage, where hydrogen is adsorbed onto the interior surfaces of a porous material. The stored hydrogen can then be released by heat, electricity, or chemical reaction. Many metals are capable of absorbing hydrogen as well. The storage of gas in solids is not only an intriguing alternative for hydrogen storage but other types of gases, such as carbon dioxide and other environmentally important gases as well. Gas storage in solids is quickly becoming an important technology, with applications ranging from energy and the environment to biology and medicine. A new review article describes the types of material that make good porous gas storage materials, why different porous solids are good for the storage of different gases, and what criteria need to be met to make a useable gas storage material.
Optical imaging of materials is full with rich physical, chemical and biological information about the sample, because the optical energies in the visible range coincide with the atomic and molecular transition energies of many materials. Apart from the topographical information, the optical image therefore contains information about intrinsic properties of a material. However, the wave nature of light prevents the light to focus in a volume smaller than half of the wavelength, which is about 200-300 nm for visible light. Therefore, it is almost impossible to image nanomaterials, which could be a few nanometers in size, using optical imaging process. A typical lens made of, for example glass, will not be sufficient to image a nanomaterial. In work that gives rise to a new concept of a lens for optical imaging, scientists in Japan have proposed a lens made of silver nanorods, rather than a curved glass surface. This metallic nanolens is capable of manipulating light in such a way that an optical image of nanoscale objects can be obtained in the visible range.
You might have seen our news item from a few days ago about BMW's shape shifting concept car. NASA has worked on something much more revolutionary, called the 'Morphing' program, for a few years already. The idea is that aircraft of the future will not be built of traditional, multiple, mechanically connected parts and systems. Instead, aircraft wing construction will employ fully-integrated, nanotechnology enabled embedded 'smart' materials and actuators that will enable aircraft wings with unprecedented levels of aerodynamic efficiencies and aircraft control. Able to respond to the constantly varying conditions of flight, sensors will act like the nerves in a bird's wing and will measure the pressure over the entire surface of the wing. The response to these measurements will direct actuators, which will function like the bird's wing muscles. Just as a bird instinctively uses different feathers on its wings to control its flight, the actuators will change the shape of the aircraft's wings to continually optimize flying conditions. Active flow control effectors will help mitigate adverse aircraft motions when turbulent air conditions are encountered.