Future development of microelectronics, magnetic recording devices, and chemical sensors will be achieved by increasing the packing density of device components. For example, high-speed electrical circuits will be produced by increasing the packing density of nanometer-scaled circuit elements. While present lithographic technology can produce nanoscale assembly in two-dimensions, a new generation of more densely packed devices requires three-dimensional assembly. This requires placement of the components in the exact positions necessary with high reproducibility.

We introduce a new method to fabricate devices such as electronics, autonomous devices and magnetic recording media using biological functions. Our strategy is to use peptide nanotubes, which can recognize and selectively bind a well-defined region on patterned substrates, as building blocks to assemble three-dimensional nanoscale architectures at uniquely defined positions and then decorate the peptide nanotubes with various materials such as metals, semiconductors, quantum dots, and/or insulators to fabricate complex device configurations. We have demonstrated that the nanotubes can be immobilized on surfaces and functionalized as conductive wires. Important two configurations for those devices, nanotube array and bridging, were fabricated.

In addition to the nanotube metallization, we also succeeded to coat the nanotube with Au nanocrystals to fabricate the nanocrystal wire for chemical sensor. The Au nanocrystal wire preserves a hollow structure and can hold a trace of samples as a "cuvette" for micro-Raman spectroscopy. Since the nanocrystal wires were coated by the Au nanocrystals, Raman signal intensities of trace samples were enhanced 106 times due to the surface enhanced Raman effect. This enhancement should make weak signals from trace molecules detectable even in complex matrix and spectral analysis will enable us to identify material composition, molecular structure and dynamic studies. We called this nanocrystal wire as a "signal-enhancing nano-cuvette". Currently, we are assembling these nanocrystal wires as arrays to build chemical sensor devices.