Koji Tsujita

Super-Resolution Rewritable Optical Disk Having a Mask Layer Composed of Thermo-Chromic Organic Dye.

Super-resolution (SR) effects of a thermo-chromic organic dye mask layer are investigated for a rewritable disk with a Ag–In–Sb–Te phase-change recording layer. Clear SR effects were recognized in both linear and radial directions in the rewritable disk, corresponding to a capacity of 10.3 GB in a 120 mm disk. A carrier-to-noise ratio over 35 dB was obtained at a short mark length of 0.2 µm. Crescent-shaped marks, which are typically recognized in high-density magneto-optical (MO) media, were observed in the phase-change recording layer. The SR effects mainly operate on the reading process, resulting from a large non-linear transmittance change in the organic dye.

Ultrahigh-Sensitivity Biomarker Sensing System Based on the Combination of Optical Disc Technologies and Nanobead Technologies

The detection of biomarkers in body fluids is useful for the early detection of diseases or preventive medical care. Various types of equipment that detect biomarkers have been developed and used for various occasions. It is expected that further improvement of the detection sensitivity of biomarkers will enable the extension for their applications to various diseases. In this paper, we propose a new biomarker sensing system with higher sensitivity. In the system, by combining optical disc technologies and nanobead technologies, we developed a new sensing method. Target biomarkers are specifically immobilized onto the optical disc surface through an antigen-antibody reaction, then the nanobeads are immobilized on top of the biomarkers. Since the biomarkers and beads bind to each other one-on-one, the number of target biomarkers can be measured by counting the number of nanobeads using an optical pickup. The most significant advantage of this method is that measurement can be carried out in a fully digital scheme, in contrast to current sensing systems which measure light intensity in an analog scheme.

Practical Properties of Thermochromically Induced Super-Resolution Read-Only Memory Disk (TSR-ROM)

Super-resolution effects and practical properties of a thermochromic mask layer for a read-only memory disk are evaluated using a conventional disk tester with a 635 nm light source and a 0.6 numerical aperture (NA) pickup. A carrier-to-noise ratio (C/N) of over 40 dB is obtained at a pit length of 0.20 µm which is far smaller than the resolution limit. Sufficient tilt margins and power margin are obtained at the capacity of 11 GB.

Thermochromic Super-Resolution in Phase-Change Rewritable Disk with Double Mask Layer

A new mask system for a thermochromically induced super-resolution (TSR) rewritable disk is proposed. In this system which consists of a high-sensitivity mask layer and a low-sensitivity mask layer, TSR effects are obtained in both read and write processes. At the high-density recording on a Ag–In–Sb–Te phase-change rewritable disk, cross-talk and cross-erase are improved.

Development of a Highly Sensitive Device for Counting the Number of Disease-Specific Exosomes in Human Sera

BACKGROUND Although circulating exosomes in blood play crucial roles in cancer development and progression, difficulties in quantifying exosomes hamper their application for reliable clinical testing. By combining the properties of nanobeads with optical disc technology, we have developed a novel device named the ExoCounter to determine the exact number of exosomes in the sera of patients with various types of cancer. METHOD In this system, individual exosomes were captured in the groove of an optical disc coated with antibodies against exosome surface antigens. The captured exosomes were labeled with antibody-conjugated magnetic nanobeads, and the number of the labeled exosomes was counted with an optical disc drive. RESULTS We showed that the ExoCounter could detect specific exosomes derived from cells or human serum without any enrichment procedures. The detection sensitivity and linearity with this system were higher than those with conventional detection methods such as ELISA or flow cytometry. In addition to the ubiquitous exosome markers CD9 and CD63, the cancer-related antigens CD147, carcinoembryonic antigen, and human epidermal growth factor receptor 2 (HER2) were also used to quantify cancer cell line-derived exosomes. Furthermore, analyses of a cross-sectional cohort of sera samples revealed that HER2-positive exosomes were significantly increased in patients with breast cancer or ovarian cancer compared with healthy individuals and those with noncancer diseases. CONCLUSIONS The ExoCounter system exhibits high performance in the direct detection of exosomes in cell culture and human sera. This method may enable reliable analysis of liquid biopsies.

Dual-Layer Recordable Digital Versatile Disc Having Protruded Land Pre Pit in L1 Layer Fabricated by Inverse Stack Method

The dual-layer recordable digital versatile disc (DVD-R DL) fabricated by an inverse stack method has not been released in the market because of unstable land pre pit (LPP) addressing in an L1 layer due to its peculiar disc structure. We have developed a DVD-R DL disc that has the novel shape of the protruded LPP in the L1 layer fabricated by an inverse stack method. The height of the protruded LPP is larger than the land height of the L1 substrate to restrain extensions in the radial direction of recording marks. We have confirmed that the protruded LPP disc satisfies the specifications of DVD-R DL and enables stable LPP addressing.