If you have seen the movie The Matrix then you are familiar with 'jacking in' - a brain-machine neural interface that connects a human brain to a computer network. For the time being, this is still a sci-fi scenario, but don't think that researchers are not heavily working on it. What is already reality today is something called neuroprosthetics, an area of neuroscience that uses artificial microdevices to replace the function of impaired nervous systems or sensory organs. Different biomedical devices implanted in the central nervous system, so-called neural interfaces, already have been developed to control motor disorders or to translate willful brain processes into specific actions by the control of external devices. These implants could help increase the independence of people with disabilities by allowing them to control various devices with their thoughts (not surprisingly, the other candidate for early adoption of this technology is the military). The potential of nanotechnology application in neuroscience is widely accepted. Especially single-walled carbon nanotubes (SWCNT) have received great attention because of their unique physical and chemical features, which allow the development of devices with outstanding electrical properties. In a crucial step towards a new generation of future neuroprosthetic devices, a group of European scientists developed a SWCNT/neuron hybrid system and demonstrated that carbon nanotubes can directly stimulate brain circuit activity.
Continuing miniaturization has moved the semiconductor industry into the nano realm with leading chip manufacturers well on their way to CPUs using 32nm process technology (expected by 2009). There are some real challenges ahead for chip designers, particularly in moving deeper and deeper into the nanoscale, where at some point in the near future they will reach physical limits of the traditional logic MOSFET (metal-oxide-semiconductor field-effect transistor) structure. In addition to physical barriers, semiconductor companies will also reach economic barriers where profitability will be squeezed hard in view of the exorbitant costs of building the necessary manufacturing capabilities if present day technologies are extrapolated. Quantum and coherence effects, high electric fields creating avalanche dielectric breakdowns, heat dissipation problems in closely packed structures and the relevance of single atom defects are all roadblocks along the current road of miniaturization. Enter nanoelectronics (note that microelectronics, even if the gate size of the transistor is below 100 nm, is not an implementation of nanoelectronics, as no new qualitative physical property related to reduction in size are being exploited). Its goal is to process, transmit and store information by taking advantage of properties of matter that are distinctly different from macroscopic properties. Understanding nanoscale transport and being able to model and simulate nanodevices requires an entirely new generation of simulation tools and techniques.
Biomarkers are of increasing importance in modern medicine for the purpose of early detection and diagnosis of a disease, for instance cancer. Biomarkers are mostly protein molecules that can be measured in blood, other body fluids, and tissues to assess the presence or state of a disease. For example, the presence of an antibody may indicate an infection or an antigen, such as PSA, might indicate the presence of prostate-specific cancer cells. Although protein-based approaches to early detection and diagnosis of cancer have a clear advantage over other, more invasive, methods, protein detection is a challenging problem owing to the structural diversity and complexity of the target analytes. State-of-the-art detection methods have limited application due to their high production cost and instability. Another limitation of current proteomic diagnostics is the limitation of arrays to one or a few markers only; in other words, you can only test for the specific markers that you are looking for and not generally measure levels of proteins in your blood in order to detect anomalies. A novel nanotechnology based protein detector array could change that.
Nanotechnology will play an important role in future space missions. Nanosensors, dramatically improved high-performance materials, or highly efficient propulsion systems are but a few examples. In previous Nanowerk Spotlights we reported about nanotechnology propulsion technology, such as nano field emission thrusters, and the use of carbon nanotubes to harden electronic components in space. This last aspect, radiation shielding, is also where nanotechnology could make a major contribution to human space flight. NASA says that the risks of exposure to space radiation are the most significant factor limiting humans’ ability to participate in long-duration space missions. A lot of research therefore focuses on developing countermeasures to protect astronauts from those risks. To meet the needs for radiation protection as well as other requirements such as low weight and structural stability, spacecraft designers are looking for materials that help them develop multifunctional spacecraft hulls. Advanced nanomaterials such as the newly developed, isotopically enriched boron nanotubes could pave the path to future spacecraft with nanosensor-integrated hulls that provide effective radiation shielding as well as energy storage.
Nanoimprinting lithography (NIL) is a simple pattern transfer process that is emerging as an alternative nanopatterning technology to traditional photolithography. NIL allows the fabrication of two-dimensional or three-dimensional structures with submicrometer resolution and the patterning and modification of functional materials. A key benefit of nanoimprint lithography is its sheer simplicity. There is no need for complex optics or high-energy radiation sources with a nanoimprint tool. There is no need for finely tailored photoresists designed for both resolution and sensitivity at a given wavelength. The simplified requirements of the technology allow low-cost, high-throughput production processes of various nanostructures with operational ease. NIL already has been applied in various fields such as biological nanodevices, nanophotonic devices, organic electronics, and the patterning of magnetic materials. Researchers at Berkeley have taken this process one step further by demonstrating that direct nanoimprinting of metal nanoparticles enables low temperature metal deposition as well as high-resolution patterning. This approach has substantial potential to take advantage of nanoimprinting for the application in ultralow cost, large area printed electronics.
Bone is one of the most fascinating materials that has evolved in nature. There are 206 bones in your body - did you know that a newborn has 350 bones but they fuse together as you grow? - more than half of them in your hands and feet. These bones not only protect your organs, support your body against gravity's pull and allow you to move but they also are living tissues that produce blood cells and store important minerals. Not only important for humans, bones are the essential part of the endoskeleton of all vertebrates. Bone is a composite material of the mineral calcium hydroxyapatite and tropocollagen molecules (the fragile and soluble form of collagen when first synthesized by fibroblasts). It forms an extremely tough, yet lightweight material and its properties and behavior are of great interest to scientists and materials engineers. For instance, very little is known about the fracture behavior of bone and all such studies have been conducted at scales much larger than the nanoscale that explicitly considers individual tropocollagen molecules and mineral particles. New research at MIT has discovered a previously unknown toughening mechanism of bone that operates at the nanoscale - the level of individual collagen molecules and nano-platelets of hydroxyapatite. This breakthrough work lays the foundation for new materials design that includes the nanostructure as a specific 'design variable' and may help engineers to design materials from the bottom up by including hierarchies as a design parameter.
In chemotherapy doctors are using a carpet bombing approach to destroy cancer cells: the patient is pumped full of cytotoxic drugs, that go everywhere in the body, with the hope that enough of the drugs reach the cancer cells and target their nuclear DNA to damage it or destroy the cell. Not only do chemotherapeutic techniques have a range of often serious side effects, mainly affecting all the fast-dividing cells of the body, it also has been shown that often less than 1% of the administered drug molecules enter tumor cells and bind to the nuclear DNA. Another complication is drug resistance of cancer cells. This actually is one of the main causes of failure in the treatment of cancer. Dividing cancer cells acquire genetic changes at a high rate, which means that the cells in a tumor that are resistant to a particular drug will survive and multiply. The result is the re-growth of a tumor that is not sensitive to the original drug. Cancer researchers are looking to nanoparticles as a drug carrier capable of localizing and directly releasing drugs into the cell nucleus, thereby circumventing the multidrug-resistance and intracellular drug-resistance mechanisms to effectively deliver drugs to the vicinity of DNA, leading to a high therapeutic efficacy. Scientists now have developed nanoparticles capable of localizing into the nucleus, giving hope to a much more effective cancer chemotherapy that allows to pinpoint individual cells.
A lot of buzz has been created by the term "green nanotechnology". In a broad sense, this term includes a wide range of possible applications, from nanotechnology-enabled, environmentally friendly manufacturing processes that reduce waste products (ultimately leading to atomically precise molecular manufacturing with zero waste); the use of nanomaterials as catalysts for greater efficiency in current manufacturing processes by minimizing or eliminating the use of toxic materials (green chemistry principles); the use of nanomaterials and nanodevices to reduce pollution (e.g. water and air filters); and the use of nanomaterials for more efficient alternative energy production (e.g. solar and fuel cells). Unfortunately, there is a flip side to these benefits. As scientists experiment with the development of new chemical or physical methods to produce nanomaterials, the concern for a negative impact on the environment is also heightened: some of the chemical procedures involved in the synthesis of nanomaterials use toxic solvents, could potentially generate hazardous byproducts, and often involve high energy consumption (not to mention the unsolved issue of the potential toxicity of certain nanomaterials). This is leading to a growing awareness of the need to develop clean, nontoxic and environmentally friendly procedures for synthesis and assembly of nanoparticles. Scientists are now exploring the use of biological organisms to literally grow nanomaterials.