Quantum Measurement and Instrumentation Laboratory (Ogi Laboratory)

Mechanical Behavior of Nanomaterials and Biomolecules Studied by Original Phonon-Photon Measurement systems, and Development of Phonon Instruments for Diagnosis and Drag Discovery

Using our original optical-acoustical measurement systems, we study mechanical behavior of nanomaterials and kinetics of biomolecules, and develop instruments for diagnosis and drug discovery. One important keyword is “resonance”. At resonance, information on mechanical and electromagnetical properties are highly enhanced, allowing high-sensitive measurements in material-biological science. We control sound via light and vice versa to investigate thermodynamic properties in nanofilms, nanowires, and nanodots, and binding and aggregation reactions among various biomolecules. We also study application of our original phonon-photon measurements for biosensors and diagnosis for neurodegenerative diseases, including Alzheimer's disease.

Nano-mechanics Group

Many functional nanomaterials, including nanofilms, nanowires, and nanodots, have been recently developed, resulting in revolutionary communication instruments and sensors. Their mechanical properties are important in designing these devices. Especially, the elastic constant is the key parameter for resonator devices in telecommunication equipment. However, it has never straightforward to measure the elastic constants of nanomaterials; we can not apply conventional measurement methods to such a tiny specimen. We then study opto-acoustical systems (picosecond ultrasonics) for causing ultrahigh-frequency (~500 GHz) ultrasounds in nanomaterials and for precisely measuring their elastic constants.

Figure 1　Optics for picosecond ultrasonics.

Figure 2　Principle of backward diffraction of probe light by ultrasonic strain pulse.

Figure 3　Brillouin oscillation caused by diffracted light by propagating ultrasound. (Upper) Ultrasonic strain pulse propagating in the thickness direction, and (Lower) corresponding reflectivity change of the probe pulse caused by the moving strain.

Phononic Biosensor Group

Early detection of biomarkers allows effective treatment for corresponding diseases. Also, when a target material is identified for a disease, it is possible to search a drug material, which shows high affinity to the target material. Biosensors are adopted for these purposes; diagnosis and drug discovery. We study label-free phononic biosensors for ultrahigh-sensitive detection of biomarkers and precise measurement of affinity among biomolecules.

Figure 4　Principle of resonator biosensor. The resonance frequency of the quartz resonator decreases when target molecules are captured by antibodies immobilized on resonator surfaces because of the mass-loading effect.

Figure 5　Ultrahigh-sensitive resonator biosensor fabricated by MEMS process.

Resonant-Ultrasound-Spectroscopy (RUS) Group

The elastic constants govern deformation configuration of material when external force is applied to it. They are needed in designing from micrometer-order devices to giant buildings. Many functional materials show low crystallographic symmetry and possess many independent elastic constants. For example, beta Ga2O3, which is an important material for power electric devices, exhibits 13 independent elastic constants, and all of them are needed for precise design of such a device. We study a methodology to determine all the independent elastic constants from a single small specimen by measuring many mechanical resonance frequencies: They include information of all the independent elastic constants and we can determine the elastic constants through an inverse calculation. Even at low temperatures (~1 K) or at high temperatures (~1300 K), the elastic constants can be obtained with this method, contributing to understanding thermodynamic properties of materials and also to device designing.

Figure 6　Specimen on the tripod ultrasonic transducers and its mechanical resonance spectra.

Protein Science and Development of Instrument for Diagnosis for Neurodegenerative Disease

Alzheimer’s disease is caused by neurotoxic aggregates of amyloid beta peptides. The aggregation reaction takes a very long time in vivo, which prevents us from studying detailed mechanism of the aggregation reaction. We however revealed that an ultrasound irradiation at specific frequency and pressure can drastically accelerate the aggregation reaction, and we apply this phenomenon to development of an instrument for diagnosis for neurodegenerative disease. Monitoring the aggregation reaction in real time under ultrasonication, it is possible to discuss its mechanism from single molecules.

Figure 7　(Left) Total internal reflection fluorescence microscope (TIRFM) coupled with the wireless-electrodeless ultrasonic resonator. (Right) Fibril-like aggregates of Alzheimer-disease peptides on the resonator.

Development of Point Diffraction Interferometer (PDI) with spherical wavefronts from optical fibers

Figure 8 shows the result of a measurement on a 200 mm diameter concave mirror surface with nanometer accuracy using light from the tip of an optical fiber. Light coming from the tip of an optical fiber propagates as diffracted spherical wave, which can be considered as a perfect sphere. Measurement on a spherical mirror to determine the accuracy of the finished sphere at a sub-nanometer scale is possible using a Point Diffraction Interferometer (PDI) with this spherical light wave as the reference wavefronts. With this high precision PDI, it is also plausible to measure and evaluate most advanced mirrors used in synchrotron facilities and gravitational wave detectors.

Figure 8 Two dimensional map of deviation from the perfect sphere of a concave mirror with a 200 mm diameter and 1500 mm radius of curvature.