Trend study on nanotechnology
The government positioned nanotechnology as one of the four key sectors in its 2001 science and technology basic plan. Since then, various nanotechnology research projects have borne fruit, and unexpected phenomena have been discovered and new technology has also been developed. These research results have begun to show the direction in which nanotechnology should be developed. The amount of research reported in basic nanotechnology, nanobiotechnology, nanomaterial technology and information technology has risen sharply over the past couple of years.
The trend study on nanotechnology was conducted to clarify the favorite technologies of Japanese research institutes/companies and to predict industrial technology based on their favorite technologies, by exhaustively collecting information about and analyzing recent nanotechnology research activities in Japan. This study was also intended to help the government plan its science and technology policy, including the next science and technology basic plan and research support programs.
1. Basic technology
1.1 Nanoscale measurement
Scanning tunneling microscopes (STMs), atomic force microscopes (AFMs), near-field optical microscopes, transmission electron microscopes (TEMs), multi-nanoprobe-based measurements and TEM-SPM (scanning probe microscope) with nanoprobes are discussed as measurement instruments or methods to see structures of materials at nanometer-level spatial resolution and to evaluate their properties. The technological aspect of near-field optical microscopes is described in detail. The main challenge with such microscopes for further development is not only the improvement of their performance under ideal conditions but also the realization of measurements with high repeatability under a wide range of measurement conditions. The microscopes may also be used for determination of electronic states in complex systems, controlled wave function engineering of the quantum state, and creation of quantum devices in the future through combining with spectroscopic technology. Information about electron correlation may be obtained through nanoscale measurements using four-nanoprobes.
1.2 Nano-processing
The present situations of both top-down and bottom-up types of nano-processing technology are reported. The manufacturing process of commercial nanodevices through top-down nano-processing is expected to remain as the main processing as far as semiconductor ultra-fine processing is concerned. This perspective is based on the assumption that significant progress in resolving technological problems will be made. Ultra-thin film-based semiconductor manufacturing technology, femtosecond laser processing, and nano-processing using STM, AFM, atom beam, TEM, or electron beam are discussed in each section.
1.3 Nano-simulation
Analyses of surface superstructures and admolecules, distribution of the electron wave function in semiconductor nanostructures, properties of liquid polymers and other achievements have been made through first-principle and molecular dynamics calculations. However, there remain many physical-chemical phenomena that cannot be handled easily. Such phenomena include dynamics of excited electrons, the origin of high-temperature superconductivity, theoretical analysis of STM, the folding structure of gigantic proteins and dynamics in the catalytic reaction field. The key trend in the nano-simulation field is the change from ground state analysis to excited state analysis and from static to dynamic structures.
2. Life science and medicine
2.1 Biocompatible materials
Silk fibroin and many other materials produced by organisms are highly biocompatible. Research on adding new functions to these organism-derived materials has been conducted. These materials have strictly ordered structures due to self-assembly. Their self-assembling characteristics may be used for fabrication of nanostructures through the bottom-up approach. This method can be relatively easily applied to the commercialization of nanostructures because it requires no molecular manipulation. Research on organic polymers as carriers in a targeting drug delivery system by making use of organic polymers’ self-assembling ability has been reported. A study on organic polymers as a nonvirus-type gene-transferring vector has also been reported. Regarding protein separation materials, research on the specific adsorption of protein on its surface or its molecular structure has been carried out.
Studying biocompatible materials is very important to develop basic technology in regenerative medicine. Such materials will be used not only as implant materials but also as scaffolding materials for supporting implanted tissues grown in vitro. Biocompatible materials may also be developed as materials with tissue reconstruction ability to rebuild deteriorated body parts. Lithography-based technology to fine-process functional polymer gel has been tested for MEMS or μ-TAS (micro total analysis system). Studies on giving new functions to such gel through molecular design have also been implemented actively. Chemo-mechanical gel, metals for artificial bones, adhesives for the human body, complexes of self-assembled inorganic polymer and integration of cell-membrane-like polymer are discussed in each section.
2.2 Overview of tissue regeneration technology
Because an existing method to regenerate tissue structures by using biodegradable polymer as their scaffoldings cannot sufficiently meet various needs, new technology to reconstruct tissue structures without using any scaffolding has been proposed. It involves covalently fixing on the surface of a culture plate a nanometer-thick layer of temperature-responsive polymer whose hydrophilic property changes drastically depending on temperature. In this way, all cultured cells in the form of a sheet can be recovered without destroying their intercellular adhesion and extracellular matrix. A sheet of cardiac muscle cells with high pulsation ability, for instance, can be recovered. Nanotechnology is expected to play a central role in this field. Such nanotechnology includes technology to control the thickness of a graft layer at the nanometer level and uniformly modify the surface of the layer, which is large enough for transplanting. Nanotechnology to develop culture plates on which various types of cell growth factors with changing their position and orientation are fixed will also be included. Tissue engineering, artificial corneas, artificial pancreases, artificial skin, artificial mucous membranes inside the oral cavity, artificial cardiac muscles and in vitro regenerated cartilage are each discussed separately.
2.3 Overview of nanoparticles and DDS
Drug delivery systems (DDSs) are an effective drug dispensing technology to deliver a minimum amount of medicine to a target part quickly, while curbing the drug's side effects. Such systems are being developed mainly to cure cancer. There are two types of such systems. One is a passive targeting system based on the characteristics of solid cancer tissue (EPR (enhanced permeability and retention) effect), and the other is an active targeting system for the target tissue. Polymer micell containing antibodies or sugar, or liposomes are being studied for active targeting systems. DDS methods that activate medicine with external stimuli such as light and heat against the target tissue or with in vivo chemical stimulus (pH) are also being studied. DDS effectiveness is being clarified in clinical tests. DDS’s using new types of medicine such as nucleic acid (antisense DNA or siRNA) and genes may be developed in the future.
Cancer treatment using polymer DDS, designing of supramolecular materials for DDS, double-targeting systems, hydrogel biodegradable nanocarriers, bio-functions of water soluble fullerene, properties of mesoporous silica-based nanomaterials and diagnosis by using nanoparticles are also discussed.
2.4 Biomolecule detection technology
Biosensors have been developed as a result of convergence technology of biochemistry, physical chemistry and electrochemistry. Quartz crystal microbalance, clarification of the laminar interfacial phenomenon, enzyme sensors, immunity sensors, antibody sensors, modification of natural enzyme/antibody, molecular modulation and other types of basic technology in this field are being established. Cell biosensors, which are used to detect molecular signals transmitted by cells for estimating the impact of external stimulation on the organism, are likely to be developed. Designing an artificial enzyme, its application to biomolecule measurements, medical checkup chips used at home, DNA chips, electrophoresis chips, immunity chips, cell chips and single molecule measurements are also discussed.
2.5 DNA and nanotechnology
Controlling two-dimensional arrays of fine particles by using DNA as a template, controlling electric resistance through iodine doping and ultra-fine line wiring by electroless-plating DNA molecules with gold or copper are being researched. There are limits in gene analysis due to the present biochemical technique, and therefore, single-molecule-based high-speed DNA sequencing and gene mapping of single molecules will be required in the future. DNA has a very ordered structure and self-assembling ability based on base-pairing. Such characteristics may be used for arraying molecules very accurately in the order of nanometers. Such fine arraying technology is likely to be the basic technology to develop molecular electronic devices and molecular machines. Construction technology of DNA electronic circuits, visualization technology of DNA and manipulation technology of DNA are also discussed separately.
3. Information technology
Fine lines with a width of about 100 nm can be drawn with optical lithography and those with some 10 nm are possible with electronic lithography. While various challenges must be addressed to draw finer lines, ideas about nanoelectronic devices based on a new concept have been proposed. They include single-electron devices, atomic switches, molecular devices, spintronics memory devices and tunneling magneto-resistance devices. The present top-down-type semiconductor integrated circuits are expected to continue playing a key role unless alternative high-performance devices are developed. Competition in developing nanoelectronic devices, however, will become fiercer. Technology to manufacture ULSIs is often seen as a typical top-down nanotechnology, but manufacturing LSIs only with fine processing technology is said to be over, because the scaling-down of ULSIs will be impossible without controlling the nanoscale properties of materials. At the same time, nano-evaluation technology and nano-simulation technology are also indispensable.
Large-scale integrated circuits (ULSIs and MOSFETs), single-electron devices (possibility of making single-electron transistors, coupled quantum dots, single-electron inverters and spin quantum bits), molecular devices, atomic switches, spintronics devices, probe memory, quantum computers, semiconductor light-emitting devices (quantum dots, quantum wires and quantum wells), carbon nanotube-based light-emitting devices, nanophotonic devices and micro-nanosystems (MEMS and NEMS) are discussed.
4. Nanomaterials
4.1 Metallic nanomaterials
The properties of metallic materials change easily, depending on their microstructures. Nanomaterials whose structures are controlled at the nanometer level have been found to show very excellent properties not found in existing metallic materials. Researchers are paying attention to controlling the nanostructures of metal and to nanostructured composite materials. They are studying the deformation mechanism of these new materials. Some challenges to manufacture them commercially must be addressed. Metallic nanoparticles and nanoclusters are discussed in this section as well.
4.2 Ceramic nanomaterials
High-precision processing of ceramic nanomaterials through laser ablation is being researched. The application of ceramic nanomaterials to ultra-high-density optical recording media by forming a laser-induced structure inside glass is also being studied. Research on photonic crystals and nonlinear optical glass from ceramic nanomaterials is underway. Colloid-sol is used to coat indeterminate ceramic nanomaterials. Fabrication of porous titanium oxide and fine particle dispersions is being researched as an application of the phase-splitting phenomenon. Preparation of three-dimensional nanostructured films from aluminum films is being studied as an application of anodizing.
The vapor phase synthesis, laser-induced structure method, etching, anodizing, crystallization and phase-splitting method are each described in detail separately as nanoglass fabrication methods. Regarding nanoceramic tubes, 15 types of metal oxide nanotubes fabricated so far and MCM41 are explained. Fabrication of single nanotubes and ceramic nanotubes with smaller diameters is also described.
4.3 Carbon nanomaterials
Carbon nanotubes (CNTs) are typical nanomaterials. The commercialization of CNT-based field-emission-type electron sources, probe-tips of scanning probe microscopes and conductive composite materials will be realized in the near future. Technology to chemically modify fullerene by attaching functional groups to it, and technology to modify fullerene frameworks have been developed. Application of fullerene to artificial photosynthesis, photoelectric conversion, gas adsorption and fuel cells is being studied. Nanotubes containing fullerene molecules, “peapods” and fullerene nanowhiskers, or fine whiskers made of fullerene molecules, were also discovered recently. CNT SPM probes, CNT composite materials, fullerene and fullerene nanowhiskers are discussed in each section.
4.4 Self-repairing materials
Rebinding of polymer molecular chains, self-repairing of cracks on ceramic surfaces, self-repairing of creep void in heat-resistant steel and self-repairing of anticorrosion coating are described in the report.
5. Applications of nanomaterials
5.1 Applications in energy and environment fields
Superconducting materials, permanent magnets using high-temperature superconductors, ultra-powerful motors and high-density hydrogen storage technology using complex hydrides are described. The hydrogen absorption characteristics of nanostructured alloys, solid polymer fuel cells, ion perforated films, nano-porous material-based gas sensors and volatile organic compound (VOC) sensors using organic/inorganic hybrid materials are also described.
5.2 Materials for safe and security-related technology
Heaters with self-temperature adjustment functions, sterilization and antifogging treatment for medicine by electron beam irradiation and active materials using phase transformation are discussed. Multifunctional materials with a closed-cell structure, in which different types of materials are introduced, are also discussed.
5.3 Application to materials used in daily life
Air purification with cluster ions generated by atmospheric pressure-discharge plasmas, cosmetics made through nanotechnology, fabrication of an ultra-multilayered structure and its application to fibers, and fabrics containing sweat deodorizers are described. Development of fibers made of sandwiched layers of oil and water containing anti-oxidant vitamin E derivative, nylon with improved moisture absorption, exhaust gas cleaning equipment which regenerate noble metal catalysts and cosmetic ingredients using fullerene are described.
An overview of the macroscopic trend in nanomaterial research appears at the end of the report.
- For the report written in Japanese: http://www.nanonet.go.jp/japanese/info/file/rep20060125.pdf
