Masayoshi Nishiyama

Detection of Glypican-3 Proteins for Hepatocellular Carcinoma Marker Using Wireless-Electrodeless Quartz-Crystal Microbalance

Pure shear-wave resonances were excited and detected in 18- and 30-µm-thick electrodeless AT-cut quartz plates in liquids using line antennas contactlessly, achieving high-frequency quartz-crystal microbalances (QCMs). Their fundamental resonance frequencies (85 and 54 MHz) were monitored to study interactions in real time between human glypican-3 and an anti-glypican-3 antibody: glypican-3 is a prospective protein marker for hepatocellular carcinoma. Their affinity was determined by the Langmuir kinetics. This study demonstrates the high ability of the wireless-electrodeless QCM for detection of the protein markers and development of drugs for disorders.

Elastic stiffness of L10 FePt thin film studied by picosecond ultrasonics

The elastic stiffness of epitaxial and polycrystalline L10 FePt films is studied by picosecond ultrasonics coupled with x-ray reflectivity analysis, and we find that C33 of L10 FePt is 309 GPa. The morphology of FePt films shows dependence on the film thickness; as the film thickness increases the mazelike structure changes to a continuous film. The elastic stiffness correlates with the morphology change, and it increases as the film thickness increases. When the film thickness exceeds 40 nm, the elastic stiffness becomes independent of the film thickness, and we define the saturated value as C33 of L10 FePt.

High-Frequency Electrodeless Quartz Crystal Microbalance Chip with a Bare Quartz Resonator Encapsulated in a Silicon Microchannel

We present a high-frequency electrodeless quartz crystal microbalance (QCM) chip with a bare quartz resonator encapsulated in a silicon microchannel, which is fabricated by micromachining technology. This QCM chip packages an AT-cut quartz plate 2.5 mm long, 1.7 mm wide, and 9.6 µm thick, which is supported by micropillars without fixed parts. There is no issue about destruction during assembly because handling the fragile quartz resonator becomes unnecessary. The quartz resonator is electrodeless and not fixed; therefore, there are no losses due to electrodes and contacting wires. As a result, a high quality factor (Q-factor) and a high signal-to-noise ratio (SNR) can be obtained. The Q-factor is about 800–2800 at 170 MHz in the flow of the carrier solution. In addition, it is possible to reuse the device, because the quartz surfaces can adsorb receptor proteins nonspecifically, which can be removed by a washing procedure with a strong acid solution flowed in the microchannel. The high-frequency quartz resonator (170 MHz) encapsulated in the microchannel can reduce the influence of the viscosity contribution to the frequency shift, achieving highly sensitive and quantitative analysis. The QCM chip is excited and detects the shear vibrations of the quartz resonator by the line antennas without contact. Consequently, both sides of the quartz resonator can be used as the detection area in a solution. We succeeded in detecting the human immunoglobulin G (hIgG) at a concentration of 6 µg/ml via the staphylococcal protein A (SPA) immobilized nonspecifically on the developed QCM chip in real time without any labeling.

Aggregation Behavior of Amyloid β1–42 Peptide Studied Using 55 MHz Wireless–Electrodeless Quartz Crystal Microbalance

A homebuilt wireless–electrodeless high frequency quartz crystal microbalance is adopted for long-time monitoring of the aggregation behavior of amyloid β1–42 peptide in a flow-cell system. The monomer amyloid peptides are immobilized on both surfaces of the crystal, and an amyloid-β solution is injected. The monotonic frequency decrease indicates aggregation on the crystal, which yields aggregation rate. Aggregation is observed even at a peptide concentration as low as 550 nM.

Development of 170 MHz Electrodeless Quartz-Crystal Microbalance Immunosensor with Nonspecifically Immobilized Receptor Proteins

Staphylococcus aureus protein A (SPA) shows high nonspecific binding affinity on a naked quartz surface, and it can be used as the receptor protein for detecting immunoglobulin G (IgG), the most important immunoglobulin. The immunosensor ability, however, significantly depends on the immobilization procedure. In this work, the effect of the nonspecific immobilization procedure on the sensor sensitivity is studied using a home-built electrodeless quartz-crystal microbalance (QCM) biosensor. The pure-shear vibration of a 9.7-µm-thick AT-cut quartz plate is excited and detected in liquids by the line antenna located outside the flow channel. SPA molecules are immobilized on the quartz surfaces, and human IgG is injected to monitor the binding reaction between SPA and IgG. This study reveals that a long (nearly 24 h) immersion procedure is required for immobilizing SPA to achieve the tight biding with the quartz surfaces.

Fast Recovery of Elastic Stiffness in Ag Thin Film Studied by Resonant-Ultrasound Spectroscopy

We studied the recovery of the elastic constant of sputtered Ag films on monocrystal Si substrates by monitoring the resonance frequency of film/substrate specimens throughout the deposition process using resonant-ultrasound spectroscopy. An Ag film is deposited on a (001) Si substrate, which is located on the tripod transducer set in the sputtering chamber. The free-vibration resonance frequency of the Ag/Si specimen is measured before, during, and after the magnetron sputtering deposition, inducing the evolution of the elastic constants of the deposited film. Recovery of the elastic constants of the Ag film is completed within 40 min. The recovery behavior of the elastic constants is similar to that of residual stress; the recovery rate is comparable to that for residual stress.

Elastic Stiffness of Co Thin Films at High Temperatures Monitored by Picosecond Ultrasound

A picosecond ultrasound system for measuring the elastic stiffness of thin films at high temperatures is developed, and the elastic stiffness of Co films is measured up to 771 K during heating and cooling processes. The elastic stiffness of an as-deposited film is smaller than that of bulk Co. However, during heating, stiffening due to crystallization is observed, and in the cooling process, the elastic stiffness follows the temperature dependence of bulk Co. These results indicate that the as-deposited film is softer than the bulk and that once stiffening has occurred upon annealing, the Co thin film shows a similar elastic property to the bulk. The temperature dependence of acoustic attenuation is also discussed.

Fast recovery of elastic constant in thin films studied by resonant-ultrasound spectroscopy

This paper reports incredibly large and rapid evolution of elastic constants in deposited copper and silver films observed by the resonant-ultrasound spectroscopy. The evolution begins just after stopping the deposition with the temperature dependent recovery rate. To explain the mechanism, we propose a model, where the elastic constants at grain boundary regions increase by 67% at least. Diffusion of atoms along the grain boundary region is a possible reason, and we confirm that the activation energy is much smaller than that for grain-boundary diffusion in bulk materials. These results are explained by drastic structure change at grain boundaries, being similar to phase transition from liquid into solid phase.