Fumio Takei

A miniature Clark-type oxygen electrode using a polyelectrolyte and its application as a glucose sensor

A miniature Clark-type oxygen electrode was fabricated by anisotropically etching silicon. A two-gold-electrode configuration was used and a double-layered gas-permeable membrane was formed directly on the electrolyte, poly(vinyl-4-ethylpyridinium bromide) in the sensitive area. These materials improved the electrodes stability in long-term storage and sterilization tolerance to a practical level. The 90% response time averaged 80 s and residual current 10%, with a good linear calibration curve. The oxygen electrode was also used to make an integrated sensor for the simultaneous determination of glucose and oxygen. The glucose sensors response time was 50-110 s, with good linearity in glucose concentrations between 56 microM and 1.1 mM at 37 degrees C, pH 7.0.

Development of a miniature clark-type oxygen electrode using semiconductor techniques and its improvement for practical applications

Abstract A disposable minature Clark-type oxygen electrode has been fabricated using semiconductor techniques. The oxygen electrode consists of: (a) anisotropically etched U- or V-grooves on a (100) silicon substrate as the electrolyte container; (b) a calcium alginate gell containing a 0.1 M KCl electrolyte; and (c) a directly formed gas-permeable membrane. A two-electrode configuration is used with a gold cathode and a gold anode. A novel fabrication process has been developed to allow miniaturization and mass production. Several important factors which influence the oxygen electrode characteristics have been examined. A 90% response time of 10 s is attained. A linear relationship is observed for a wide range of oxygen concentrations at 27°C. 34% of the oxygen electrodes work normally after sterlization in an autoclave. The oxygen electrode can be operated continuously for more than 40 h.

Disposable oxygen electrodes fabricated by semiconductor techniques and their application to biosensors

Abstract We fabricated a miniature Clark-type oxygen electrode using semiconductor techniques. The oxygen electrode features V-grooves to contain a 0.1 M KCl electrolyte impregnated in a gel, and a directly formed gas-permeable membrane over the gel. A fast response and a good linearity from zero oxygen concentration to saturation was obtained using the Ag/AgCl anode. The oxygen electrode was used in a disposable miniature CO 2 sensor. Also, an l -lysine sensor was developed that functions by immobilizing l -lysine decarboxylase on the sensitized area of the CO 2 sensor.

Chemical modification of multiwalled carbon nanotubes by vacuum ultraviolet irradiation dry process

We developed a fast dry oxidation process for chemical vapor deposition (CVD) grown multiwalled carbon nanotubes (MWNTs) using short-wavelength UV [vacuum ultraviolet (VUV) light (λmax=172 nm)] irradiation. We introduced carboxyl groups as many as 3% of carbon atoms within 1 min at room temperature using this process. MWNTs with the carboxyl groups were analyzed by attenuated total reflection (ATR) Fourier transform infrared absorption spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The attachment of the carboxyl groups was further confirmed by reacting ferritin molecules with the MWNTs. The developed dry process with a high reaction rate is a powerful tool for the applications of carbon nanotubes in nanoelectronics.