Katsuyoshi Takano

Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique

Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin–avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin–biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.

Micrometer-Sized Magnetic Patterning of FeRh Films Using an Energetic Ion Microbeam

FeRh thin films were irradiated with a focused 10 MeV I 2 ×2 µm2 ion microbeam at intervals of several µm. Following irradiation, the magnetic state at the surface was observed via magnetic force microscopy. The micrometer-sized regions irradiated with the microbeam show a ferromagnetic state while unirradiated regions remain in an anti-ferromagnetic state. Results indicate that an energetic ion microbeam can be used as a tool to produce micrometer-sized modulations of lateral magnetic states of FeRh films.

Demonstration of Thermo-Optic Switch Consisting of Mach-Zehnder Polymer Waveguide Drawn Using Focused Proton Beam

We demonstrated a PMMA-based thermo-optic switch consisting of a Mach-Zehnder (MZ) type waveguide drawn by proton beam writing (PBW) and working at λ = 1.55 μm. The MZ waveguide was drawn by symmetrically coupling two Y junctions with a core width of 8 μm and a branching angle of 2°. A Ti thin-film heater and Al electrodes were formed on the surface of the MZ waveguide using conventional photolithography and wet-etching processes. An ON/OFF ratio of 9.0 dB and a switching power of 43.9 mW were obtained from the sample. The switching power is lower than for conventional commercial silica-based switches.

Fabrication of Mach-Zehnder Polymer Waveguides by a Direct-Drawing Technique Using a Focused Proton Beam

Proton beam writing (PBW) has recently attracted much attention as a next-generation microfabrication technology. This is a direct-drawing technique and does not need any masks to transfer micropatterns to sample surfaces. In our previous work, we demonstrated the first single-mode straight-line and Y-junction PMMA-based waveguides fabricated using PBW and working at λ = 1.55 μm. In this work, we fabricated the first PMMA-based Mach-Zehnder waveguides for the wavelength utilizing PBW in order to construct thermo-optic switches.

Fabrication of polymer optical waveguides for the 1.5-μm band using focused proton beam

Proton beam writing (PBW) has attracted much attention recently as a next-generation micro-fabrication technology. It is a direct-drawing technique and does not need any masks to transfer micro-patterns to sample surfaces. In addition, the refractive index of a poly (methyl methacrylate) (PMMA) can be increased by proton-beam irradiation. In this study, we fabricated the first 1.5-μm-band single-mode, straight-line waveguides and Y-junction waveguides consisting of PMMA layers using the PBW technique.

MFM and PEEM observation of micrometre-sized magnetic dot arrays fabricated by ion-microbeam irradiation in FeRh thin films

Micrometre-size lateral magnetic modulations were fabricated in FeRh thin films by ion-microbeam irradiation. Their magnetic domain structures were characterized by XMCD–PEEM.

Gasochromic Properties of Nanostructured Tungsten Oxide Films Prepared by Sputtering Deposition

The effects of surface morphology on the gasochromic properties of tungsten trioxide (WO3) films are reported. WO3 films with various crystalline structures and surface morphologies are prepared by reactive rf magnetron sputtering by adjusting the substrate temperature and oxygen concentration in a sputtering gas during deposition. Grain structures on these films were confirmed by atomic force microscopy observation. The gasochromic properties of the WO3 films coated with a palladium catalyst were examined on the basis of a change in optical transmittance with 645-nm-wavelength light in 1% hydrogen in argon gas. WO3 films with a (001) orientation show sufficient gasochromic properties for their application to fiber-optic hydrogen gas sensors. The growth of the nanocrystalline structure in the WO3 films seems to improve gasochromic properties.

Ion-Beam-Induced Luminescence Analysis as Diagnostic Tool for Microstructure Patterning on Diamond by Proton Beam Writing

An in situ diagnostics technique for proton beam writing (PBW) on chemical vapor deposition (CVD) diamond was newly established by developing a method of monochromatic ion-beam-induced luminescence (IBIL) analysis. As a compact optic system of IBIL analysis, a couple of optics including a monochromator and a photon counting photomultiplier were installed on the microbeam line of a 3 MV single-ended accelerator. Changes in the crystal structure of single-crystal CVD diamond were continuously monitored by observing the decay of IBIL at a wavelength related to them. Two-dimensional microscopy images of IBIL were also clearly visualized as patterns on diamond in the postprocess of PBW with the same experimental setup. The total fluence of the proton microbeam was well linked to the photon count of IBIL for the fabrication of micrometer-sized carbonized layers in the CVD diamond crystal.

Prototype of thermo-optic switch consisting of Mach-Zehnder polymer waveguide drawn by focused proton beam

In this work, we first attempted to fabricate a Mach-Zehnder type thermo-optic switch utilizing proton beam writing.

Observation of Blue Light Emission from Si Ion Implated Fused Silica Substrates

In this paper, Si ions are implanted into fused silica substrates, and the samples are annealed at 1100, 1150, and 1200degC. We demonstrate that blue photoluminescence (PL) spectra having peak wavelengths around 400 nm are generated from the samples in addition to the PL spectrum whose wavelength ranges from red to infrared. The longer-wavelength peak is reduced and only the blue PL peaks are observed from the samples after annealing above 1150degC.