Single-molecule electronics has long been expected to compete with silicon-based electronics and many efforts have been made. However, it is still impossible to fabricate a practical single-molecule integrated circuit, largely because of the lack of good methods for wiring each molecule. Several years ago, we developed a method for fabricating single conductive polymer chains at designated positions by using the probe tip of a scanning tunneling microscope (STM) to initiate chain polymerization. Using this method, we are carrying out further studies for connecting single conductive polymers to single functional molecules and other functional materials. Fabrication and characterization of such structures will enable us to fabricate novel molecular nano-systems which have excellent functions.

Scanning tunneling microscope (STM) tip is used as a tunneling electron source with the high spatial resolution. Light is created as a result of inelastic scattering of the electrons. The light includes unique information about light creation process in the tunneling gap and light propagation process from the gap to a far-field distance. The energy of the light is related to energy level of the surface states relevant to the tunnneling. The linearly polarized light includes information about orbital symmetry of the surface state. The circularly polarized light contains spin information.

Oxide and semiconductor nanowires are promising tools in future opto- and spin-electronics. We fabricate unique nanowires and nanostructures and arrange individual nanostructure into desired arrangements to achieve novel functionality. We develop the scanning probe microscope (SPM)-based technique to measure local electrical, optical, and magnetic properties of individual nanostructures. Based on the understanding of their local properties, we design nanoscale arrangement and study mutual linkage of individual nanostructure.

Biomacromolecules including proteins are functional at the molecular level. These molecules are excellent functional nanomaterials in nature. Biomaterials and biomolecules are studied as nano-machines in our group in order to unravel the mechanism of them, which is a different approach from conventional biochemistry and molecular-biology. We will develop practicable nanotechnology for biomaterials that is required for the new period of post-genome and post-proteome days. Application of the technology will start in medical, pharmaceutical and physiological fields as examination, evaluation and development techniques, and will open a way to develop novel nanodevice based on biomolecules.

Microfabricated cantilever arrays are emerging as label-free and real-time sensors for detecting tiny amount of various target molecules in parallel. Adsorption of analytes on a receptor layer coated on a cantilever surface induces surface stress, which makes the cantilever bend. This simple mechanics opened a myriad of possibilities for the use of atomic force microscopy (AFM) cantilever deflection technique beyond imaging. Applications ranging from chemistry to genomics have been demonstrated, for example, detection of volatile organic compounds, triggered marker genes, viruses, fungi, etc. In contrast to conventional optical (laser) read-out technique for the measurement of cantilever deflection, piezoresistive read-out system does not require bulky and expensive instrumentation. This approach contains various advantages, such as low cost, simple operation, miniaturization for fully integrated devices, and measurements in opaque liquid including blood. Geometrical optimization will lead to significant improvement of the sensitivity, lifting piezoresistive detection onto the same level of sensitivity as general optical methods in use, or even higher. It will open the door to a new era of medical diagnostic as well as genetic and environmental researches in the near future.