Ultrasonic measurement is an important technique that is used in various fields of science and technology, including physical property evaluation, imaging and sensing. I use a measurement technique that uses light to excite and detect ultrasonic waves in the frequency range of GHz to THz, and I use this to evaluate the mechanical and acoustic properties of microstructures and thin films with sizes in the nano to micro range, as well as for non-destructive testing.

Conventional ultrasound had a wavelength of several micrometres or more, so it was impossible to measure at the nanoscale.
However, by using femtosecond pulse lasers to manipulate ultrasound with a wavelength of the order of 10 nm, I have achieved the evaluation of the mechanical properties of nano-materials and non-destructive testing in the nano-region.

• Development of unique measurement technology that makes full use of light and sound (lasers and ultrasound)
• Excitation and detection of vibration phenomena in nano-materials and GHz bands
• Accurate measurement of sound velocity and elastic constants under high magnetic fields of 10 to 600 K and up to 5 T
• Measurement of magnetic damping constants and saturation magnetisation from magnetisation oscillations in the time domain
• Main targets include nano-thin films of metals, piezoelectric materials, and magnetic materials, as well as superhard materials such as diamond and tungsten carbide
• Contributing to the development of materials and the elucidation of the characteristics of filters for wireless communication in smartphones
• Applications include the development of highly sensitive biosensors using ultrasound, which has a shorter wavelength than light, and monitoring the breaking process of nanowires

This measurement method enables the inspection of defects in semiconductors on the order of nm, and the evaluation of the characteristics of acoustic filters, which are essential for 5G communication devices.

• Our research group investigates creation of functional oxides and their functionalities. We synthesize thin films by pulsed laser deposition and sputtering methods and bulk specimens, and develop their novel synthetic routes. Recently, we are studying electrically conducting rare earth oxides, transparent room temperature ferromagnetic semiconductors, and metal hydrides. We will develop our materials design by extending materials range and performing thin film heteroepitaxy.

Collaborative research in fields of oxide electronics with novel electric conducting oxides and oxide spintronics with ferromagnetic semiconductors and novel ferromagnetic oxides.

• One of the important challenges in the development of carbon nanotubes (CNTs) reinforced ceramic composites is uniform dispersion of CNTs in the matrix. The mechanical properties of CNT/ceramics composites have been limited to date due to the formation of CNT agglomerates in the composite. We have successfully produced CNT/alumina composites with world top class strength and toughness, by employing a newly developed CNTs dispersion technique based on a flocculation method. The processing method developed in this study enables us to prepare high performance CNT materials using a pressureless sintering method.

The possible applications of the CNT/alumina composites developed in this study include tribological materials (ball bearing), biomaterials (artificial hip joint), micro-actuator materials utilizing electrostrictive effects, electromagnetic wave absorber, particularly in the frequency range of several GHz and several ten GHz.

• Hybrid materials that show multi-functions of polymer and nanoparticles are expected to be used in future industries, and thus many research and development have been actively conducted. However, since the affinity of polymer and inorganic nanoparticles is very low, in most of the cases, properties of different materials are incompatible in the hybrid materials. To create the hybrid materials with incompatible multi-functions has been considered a difficult task.
• However, by using supercritical fluid technology, we have succeeded in making hybrid materials with incompatible multi-functions.

Now, variety of hybrid materials are being developed, including
・Transparent, flexible, high reflective index, and high fabricability,
・Flexible, high heat conductivity, low electric resistivity, and high fabricability.

• Our research aims at developing methods, including instrumentation, for characterizing surface (or interface) at the nano-meter level. Most of our research subjects are related to the surface forces measurement, which can directly monitor the interaction between two surfaces. We study phenomena occurring at the solid-liquid interface such as adsorption and structuring of liquids. We have developed the resonance shear measurement which is a sensitive method for evaluating properties of confined liquid for nano-rheology and tribology. Twin-path surface forces apparatus we developed enabled us to study wide variety of samples such as metals, ceramics and plastics.

These methods are applicable for characterizing lubricants, nano-materials, paints, sealants, and cosmetics. We hope to conduct collaborative research with a willing company for a practical application of this technology in industry.

• We developed both pH and Cl- imaging plates, which can visualize the pH and Cl- concentration on metal surfaces in acidic environments. The pH range is from 3.0 to 0.5, and Cl- concentration up to 4 M can be measured. Fluorescent dyes are successively used for pH and Cl- imaging in the field of biology, but their sensitivity tends to be insufficient in acidic and/or highly concentrated chloride solutions. A glass plate with a sol-gel sensing layer, which contains a pH indicator or a Cl- sensitive florescent dye was fabricated and validated using the solutions with various pH values and Cl- concentrations. Changes in the pH and Cl- distribution on stainless surface in an acidic environment were measured quantitatively.

The newly developed imaging plates can be used to investigate the mechanism of various chemical reactions, such as corrosion, which occurs in an acidic environment. Micro-flow imaging using our sensing technique will be a promising approach to understand the catalytic chemistry of metal surfaces.
強調

• Our goal is "bio-inspired engineering" to create new functions that exhibit functions beyond the nature systems by learning from their superior functions and incorporating them into creating materials and devices. For example, the development of surface treatment and adhesives learned from mussels, the development of anti-biofouling substrates learned from pitcher plants, the design of non-platinum catalysts for highly active fuel cells (hydrogen, enzymes, microbes, etc.) learned from hemoglobin, and needle-type biosensors learned from biological needles.

Based on electrochemistry and polymer chemistry, I provide technologies and expertise in the energy, biotechnology, and electrical and electronic fields, including metal-air batteries, fuel cells, surface treatment, adhesion, biosensors, etc.

• Nanoporous metals have drawn considerable attention due to their highly functional properties. They are generally produced by selective dissolution of elements from a multicomponent alloy (known as the dealloying method). As this method is based on differences in the electrode potential of each element present in the alloy, and this potential is high for noble metals, porous structure can be obtained only for noble metals. Recently we have found a new, simple and easy dealloying method without using aqueous solution, which enable us to develop an open nanoporous non-oxidized metallic material even with base metals (such as Ti, Ni, Cr, Fe, Mo, etc), metalloids and their alloys.

This technique is very powerful for developing new functional electrodes, catalysts, filters as well for removing toxic metallic element from the surface of biomaterials containing the toxic element.