Takeshi Hatsuzawa

Stimuli-responsive hydrogel-silver nanoparticles composite for development of localized surface plasmon resonance-based optical biosensor.

In this paper, the development of a localized surface plasmon resonance (LSPR)-based optical enzyme biosensor using stimuli-responsive hydrogel-silver nanoparticles composite is described. This optical enzyme biosensor was constructed by immobilizing glucose oxidase (GOx) into the stimuli-responsive hydrogel. When a sample solution such as glucose was applied to the surface of this optical enzyme biosensor, the interparticle distances of the silver nanoparticles present in the stimuli-responsive hydrogel were increased, and thus the absorbance strength of the LSPR was decreased. Furthermore, hydrogen peroxide, which was produced by the enzymatic reaction, induced the degradation of highly clustered silver nanoparticles by the decomposition of hydrogen peroxide. Hence, a drastic LSPR absorbance change, which depends on the glucose concentrations, could be observed. On the basis of the abovementioned mechanism, the characterization of the LSPR-based optical enzyme biosensor was carried out. It was found that the LSPR-based optical enzyme biosensor could be used to specifically determine glucose concentrations. Furthermore, the detection limit of this biosensor was 10 pM. Therefore, this LSPR-based optical enzyme biosensor has the potential to be applied in cost-effective, highly simplified, and highly sensitive test kits for medical applications.

Copper Bottom-up Deposition by Breakdown of PEG-Cl Inhibition

Copper bottom-up deposition in 200 nm trenches by an acid-copper sulfate with only two additives [poly(ethylene glycol) (PEG) and Cl ] is achieved. The inhibiting effect of electrodeposition by PEG is strongly related to Cl - concentration. Secondary-ion mass spectroscopy measurements show that Cl - is consumed in the electroplating process. The explanation of bottom-up deposition realized in copper superfilling, in which the decrease of Cl - concentration causes rapid electrodeposition on trench bottoms, is verified experimentally.

Miniature 250 μm Thick Fuel Cell with Monolithically Fabricated Silicon Electrodes

A fabrication technique of miniature fuel cell electrodes was developed from Si wafers. The fuel channels, porous layer, and catalyst layer were formed in the Si wafer. The fuel channels were fabricated by photolithographic patterning and subsequent wet etching on the Si. The porous layer was formed by anodization of Si from the polymer electrolyte membrane side through the bottom of the fuel channels. Catalyst metals were deposited inside the porous layer by wet plating. The two electrodes were hot-pressed with a Nafion 112 sheet. Open-circuit voltage of 840 mV and maximum power density of 1.5 mW/cm 2 were observed by hydrogen feed.

Preferential Copper Electrodeposition at Submicrometer Trenches by Consumption of Halide Ion

Preferential copper electrodeposition at submicrometer trenches in an acid copper sulfate electroplating bath by addition of only two components [bromide ion and polyethylene glycol (PEG)] is observed. Strong suppression by PEG is observed by the addition of Br - compared with the addition of Cl - . It is supposed that halide ions work as an adhesive between PEG and the copper surface. During electroplating, halide ions are consumed and the concentration of halide ions in submicrometer trenches is reduced by diffusional limitation. The reduction of halide ion concentration weakens the PEG adsorption and thus preferential copper electrodeposition at submicrometer trenches is realized. Nonuniform deposition observed by filling experiments is explained by this model.

Fabrication of core-shell structured nanoparticle layer substrate for excitation of localized surface plasmon resonance and its optical response for DNA in aqueous conditions

LSPR from nanostructured noble metals such as gold and silver offers great potential for biosensing applications. In this study, a core-shell structured nanoparticle layer substrate was fabricated and the localized surface plasmon resonance (LSPR) optical characteristics were investigated for DNA in aqueous conditions. Factors such as DNA length dependence, concentration dependence, and the monitoring of DNA aspects (ssDNA or dsDNA) were measured. Different lengths and concentrations of DNA solutions were introduced onto the surface of the substrate and the changes in the LSPR optical characteristics were measured. In addition, to monitor the changes in LSPR optical characteristics for different DNA aspects, a DNA solutions denatured by means of heat or alkali were introduced onto the surface, after which optical characterization of the core-shell structured nanoparticle substrate was carried out. With this core-shell structured nanoparticle layer for the excitation of LSPR, the dependence upon specific DNA conditions (length, concentration, and aspect) could be monitored. In particular, the core-shell structured nanoparticle layer substrate could detect DNA of length 100-5000 bp and 400-bp DNA at a concentration of 4.08 ng mL(-1) (1 x 10(7) DNA molecules mL(-1)). Furthermore, the changes in LSPR optical characteristics with DNA aspect could be monitored. Thus, LSPR-based optical detection using a core-shell structured nanoparticle layer substrate can be used to determine the kinetics of biomolecular interactions in a wide range of practical applications such as medicine, drug delivery, and food control.

Speed control characteristics and digital servosystem of a circular traveling wave motor

The rotational speed control characteristics of a circular traveling wave motor are investigated. This motor is an ultrasonic motor driven by a specially designed piezoelectric vibrator. There are various parameters for controlling rotational speed due to the influence of friction and resonance between rotor and stator. In this paper the dependence of rotational speed on these parameters is explored by using an experimental instrument. A digital servosystem to control the rotational position of the motor is then assembled, using the experimental results as a guide. The angular resolution of the motor is 5.4’, sufficient as a driver of a standard rotary table.

Capillary‐Assisted Fabrication of Biconcave Polymeric Microlenses from Microfluidic Ternary Emulsion Droplets

In this study, a simple capillary-based approach for producing biconcave polymeric microlenses with uniform size and shape from ternary emulsion droplets is presented. Monodisperse ternary emulsion droplets (0.6-4.0 nL) are produced which contain a photocurable segment of an acrylate monomer and two non-curable segments of silicone oil (SO) by using a microfluidic sheath-flowing droplet generator on a glass chip. The curvature radius of the interfaces separating the droplet segments, as well as the droplet size, and production rate can be flexibly varied by changing the flow conditions of the organic and aqueous phases. Subsequently, off-chip suspension photopolymerization yields non-spherical polymeric microparticles with two spherical concave surfaces templated by two SO segments at random positions. By ultraviolet light irradiation of ternary droplets with two SO segments trapped by the interior wall of a cylindrical microcapillary (internal diameter: 130 μm), biconcave microlenses can be produced with two spherical concave surfaces with a common lens axis. The produced lenses are suitable for use as optical diverging lenses.

On-Chip Single-Cell Lysis for Extracting Intracellular Material

A newly designed microfluidic chip with a pinched-channel structure and two pairs of electrodes has been developed to enable easier single-cell capture and lysis. The function of the chip was evaluated by introducing zucchini protoplast cells into the channel. In the first experiment, we attempted to break a cell using the through force of a triangular pinched structure via electroosmotic flow generated by outer electrodes. The pinched structure appeared to break the cell without applying the electric field to the cell directly; however, in this case, the breakable size of the cell was limited by the width of the pinched structure. The next attempt was to break cells regardless of their sizes using a pair of inner electrodes located under the pinched structure. The inner electrodes generated a gradient electric field around the captured cell by applying an alternative voltage to the electrodes. Captured cells with a diameter from 40 to 85 µm could be broken using the inner electrodes with a trapezoidal pinched structure, and the cells were successfully broken at 10 Vpp or less at a frequency of 1 MHz.

A metrological electron microscope system for microfeatures of very large scale integrated circuits

An absolute linewidth measuring system, based on a scanning electron microscope (SEM), is developed to measure critical dimension (CD) of VLSIs (very large scale integrated circuits). The system employs two laser interferometers for the absolute scales of the X and Y axes, while the electron beam is used to detect microfeatures on the silicon chips. The resolutions of the interferometers are 0.8 nm for X and 20 nm for Y. An LaB6 filament is used for the electron gun and the system is operated under low acceleration voltages of around 1 kV for noncharging measurements. In this article, the principle of the measurements, the electron beam system, the scanning mechanism, and the laser interferometer are described including basic experimental results.

Uniform Ni – P Film Using an Electroless Plating Method with an Emulsion of Supercritical Carbon Dioxide

This paper proposes a method for electroless plating by combining supercritical fluid technology and electroless plating in a hybrid technique. The electroless plating reactions are carried out in an emulsion of supercritical carbon dioxide and an electroless plating solution with surfactant. The Ni-P film obtained by this proposed technique was a uniform and conformal film without the pinholes that form from the hydrogen bubbles produced by the electrolysis of water, and without the nodules that form from the nuclear growth on the electroless plating reaction. The dissolution of the hydrogen bubbles in the dense CO 2 particles of the emulsion prevented the pinholes from forming. The formation of nodules might have been prevented by the transport properties of the emulsion with the diffusive dense CO 2 and the suppression of the dissolved oxygen concentration when the oxygen dissolved in the dense CO 2 particles of the emulsion. The Ni-P film fabricated by our technique was smoother and more uniform than the substrate. The roughness of the plated film was constant during film growth, whereas the surface of the film fabricated by conventional electroless plating tended to roughen as the reaction time increased.