Masayuki Suda

In-situ monitoring of microrheology on electrochemical deposition using an advanced quartz crystal analyzer and its application to polypyrrole deposition

Abstract This paper introduces a technique for studying the microrheology of a thin film on a quartz crystal by considering the contrast of the resonant frequency change and resonant resistance change of the quartz crystal. An advanced measuring system was developed for the in-situ measurement of the resonant resistance on the electrochemical reaction. The system was used to monitor polypyrrole deposition by cyclic voltammetry and the constant current method. In the electrochemical deposition, not only the resonant frequency change but also the resonant resistance increase was observed, i.e. the deposited film was a viscoelastic film. The resonant resistance was changed in the range of 100–600 Ω for the resonant frequency change of 10 000 Hz; it showed a small change in the early stage of film deposition which increased after a resonant frequency change of 5000 Hz. The swelling of the film was observed corresponding to the unusual resonant resistance increase for the constant current deposition of 6 mA cm −2 .

Piezoelectric resonator as a chemical and biochemical sensing device

Abstract This paper introduces the application of the piezoelectric resonator to a chemical and biochemical sensing. The device was used for viscosity and surface mass change measurement. Viscosity measurement was applied for gelation detection; where endotoxin and fibrinogen were determined, and also thermal analysis, where phase transition of liquid crystal was detected. Surface mass change was applied to electrochemical measurement, where Prussian blue film formation and reaction of the film were monitored, and odorant detection, in which n-amyl acetate, citral, β-ionone and menthone were detected.

Micromachined detectors for an enzyme-based FIA

Micromachining techniques were applied to construct biosensor systems. The micromachined biosensors have small size, low production cost, and good reproducibility. We made some detection units for flow injection analysis (FIA). An electrochemical flow cell was fabricated, and both the enzyme immobilized column and electrochemical detector were integrated onto the same chip. A chemiluminescence detector was also fabricated and applied to the determination of glucose and lactic acid contained in human serum and urine.

Fabrication of micro parts using only electrochemical process

We have investigated two kinds of electrochemical processes that scan a processing electrode to fabricate metal micro parts. They are, electroforming on the mold made by electrochemical processing, and shape forming by electrochemical processing after electroplating. An electroformed Ni gear with diameter of 600 /spl square/m and thickness of 100 /spl square/m was fabricated by the former method, and a Ni gear with diameter of 1700 /spl square/m and thickness of 30 /spl square/m was fabricated by the latter method.

Electrochemical and optical processing of microstructures by scanning probe microscopy (SPM)

Two micro processing techniques based on scanning probe microscopy (SPM) are described. One is electrochemical etching and deposition using a scanning tunneling microscope (STM). STM is very useful tool of nm-scaled observation, and it can be also used as precise positioner in micro processing. In micro electrochemical processing system, a potentiostat for processing is externally attached to STM system, a STM probe was set very closely to a metal substrate in electrolyte solution, and voltage was applied between the substrate and the probe. Then electrochemical reaction occurs in restricted area of the substrate. Therefore, micrometer-size structures are produced by faradic current. A line pattern, which is 200-300 nm in width and 100 nm in depth, was electrochemically etched. When polarity of applied voltage was inverted, a bump pattern, 300 nm in diameter, 200 nm in height, was electrochemically deposited. Another processing method is using a scanning near-field optic/atomic force microscope (SNOAM). The SNOAM provides simultaneous topographic and optical images with high resolution beyond the diffraction limit, better than 100 nm. The optical processing is demonstrated in the photoresist film by the SNOAM. We obtained pit and line patterns down to 100 nm in diameter and width, respectively.

Miniaturized detectors for a chemical analysis system.

Recently, several studies about miniaturized chemical analysis systems fabricated with micromachining methods were reported. These systems have some advantages, such as fast response, small amount of sample, and low consumption of reagents, as compared with the conventional system. With such a small system, design of the detector units is very important to monitor analytical performance. This paper introduces some examples of micromachined detectors for miniaturized chemical analysis systems.

Biosensors and Micromachining

Publisher Summary This chapter discusses the fabrication of detection units for enzyme-based flow injection analysis (FIA) using micromachining techniques. Because these micromachined devices are batch-processed, they can be made at low cost and with good reproducibility. The signal from the detector decreases as the detector size decreases. However, the electrochemical and chemiluminescence methods are more sensitive than the spectroscopic method. Hence, the measurable range of the micromachined detector is almost the same as for the conventional method. Additionally, the measurement could be carried out at a flow rate of less than 50 μl/min and yet the pressure drop over the column was less than 0.1 atm. This suggests the possibility of applying a micromachined pump. Thus, the conventional plunger pump and sample injector used in the experiments described above will be replaced by micromachined devices in the near future.