One can hardly pick up a popular science magazine or even a daily newspaper these days without reading about an imminent nanorevolution in science and technology. The question is will Canada be taking part?
The word nano refers to a length scale of 10-9 m, about 1/100,000 the width of a human hair. It is misleading, however, to associate the "nanorevolution" with just a length scale. In several fields of science we are clearly at a crossroads. Old technologies are reaching their limit while breathtaking scientific developments which enable us to control and manipulate single molecules, atoms, or even single electrons and photons are opening new and dramatic possibilities, concepts, and approaches. A new economy may very well rest on these scientific developments. A necessary step on this new path is a blurring of the boundaries between the old scientific disciplines of physics, chemistry, biology, and computer science. Future nanotechnologists will need to be knowledgeable in all of these areas.
Let us illustrate this exciting scenario with a couple of examples that we are familiar with at the National Research Council (NRC) of Canada in Ottawa. It is now generally accepted that, based on existing semiconductor technology, the exponential increase in the power of computers which has existed for over 30 years (i.e., computers have doubled in power every 18 months) will come to an end over the next decade as the minimum feature size in the current integrated circuit technology is reduced below 50 nm. This is the scale of the "atomic world," governed not by the laws of classical (Newtonian) physics but rather quantum mechanics.
This realization has caused scientists to seek new paradigms for future advances in electronics and computers such as single electronics, cellular automata, spintronics, and quantum computing. In spintronics, for example, one aims to make use not only of the electrical charge of an electron but also its spin. At NRC we are already beginning to combine nanoelectronics and spintronics by controlling the spin of a single electron as it passes through a nanoscale transistor. One of the most exciting applications of this as well as other nanoscale objects will be in the area of quantum computing. Quantum computers speed up operation by simultaneously storing and manipulating many pieces of classical information embedded in a quantum state of many quantum bits. Preliminary attempts at building such quantum bits and putting them together as quantum gates in a semiconductor material are well under way at NRC. Work on quantum computing brings together physicists, chemists, and computer scientists. In one sense, computer science is currently where physics was before Newton. Quantum mechanics and the science of computation have more in common than previously thought, and nanoscience may bring these two disciplines together.
The experimental quantum bits described above provide an interesting example of one of the new approaches being employed in the nanoregime. Rather than being fabricated, they simply self-assemble as nano-sized semiconductor clusters, quantum dots, during the growth of atomic layers of one semiconductor on top of another. Such a bottom up approach contrasts dramatically with the sophisticated and costly lithographic techniques currently used in the microelectronics industry. Researchers at the Institute for Microstructural Sciences at NRC are devoting a lot of effort to find ways to control this self assembly process, for example, by making the quantum dots uniform, controlling the location of their nucleation, and building quantum dot circuits.
Nature has, of course, perfected the self-assembly technique over millions of years within the human body. Research is being carried out in many institutions around the world in an attempt to utilize the self-organizing properties of molecules to build functional nanostructures based on simple organic molecules or more complex bioorganic molecules such as proteins or DNA. In a simple example from the Steacie Institute for Molecular Sciences of the NRC, it was shown that styrene molecules could be assembled into a straight line on a silicon surface in a process which is not only self-assembling but self-directing. It is hoped that processes similar to this may one day be used for assembling or interconnecting nanoscale devices.
The nanorevolution will also have a major impact on the life sciences and health care. Tools such as the atomic force microscope (AFM) provide an unprecedented view of the structure (and soon function) of living cells on the nanometer scale. By modifying the AFM tip with proteins and other ligands, researchers are directly measuring the forces exerted between single molecules as a ligand binds to a receptor. Besides using nanoworld tools to understand and manipulate biological processes, there is an exciting trend to integrate biological processes into devices. Reports, such as using F1-ATPase (a molecular motor protein that is powered by ATP) to drive an inorganic nanodevice, demonstrate that some proteins are sufficiently robust to be manipulated outside of their natural environment. A number of groups around the world are using the self-assembly properties of DNA itself to assemble nanodevices and circuits. The expected medical and health impacts of nanoscience and technology over the next several years include the development of nanosensors for implantable medical devices, nanoparticles for the controlled delivery of genes or pharmaceuticals to targeted cells, and a new generation of diagnostic/analytical tools capable of extracting, fractionating, and analyzing biological tissues and fluids.
It is clear that the potential for nanotechnology, from quantum computers to medical devices, is tremendous. All around the world multidisciplinary nanotechnology educational and research programs are being initiated. Canada is no exception. Last year the Canadian Institute for Advanced Research initiated a new program in nanotechnology. A program called CERION (Canadian European Research Initiative on Nanostructures) links Canadian and European researchers. Across the country, several universities have active nanotechnology research programs, using funds from NSERC, the Canadian Fund for Innovation, and other public and private sources to establish world-class nano-facilities. In January 2001 the NRC organized a nanotechnology workshop in Banff, Alberta, which brought many of the key players together and started to formulate a national strategy for nanotechnology R&D. The future has never looked brighter for young scientists wishing to become involved in nanotechnology.
About the authors:
Dr. Andy Sachrajda obtained his Ph.D. from the University of Sussex, England, in 1981. He currently coordinates the Semiconductor Nanodevice project within the Institute for Microstructural Sciences at the National Research Council in Ottawa.
Dr. Pawel Hawrylak obtained his Ph.D. from the University of Kentucky in 1984. He currently coordinates the Quantum Information project at the Institute for Microstructural Sciences at the National Research Council in Ottawa.
Dr. Dan Wayner obtained his Ph.D. from Dalhousie University, Canada, in 1984. He currently leads the Molecular Interfaces group within the Steacie Institute for Molecular Sciences at the National Research Council in Ottawa.