This article has no abstract.

View full abstract

Bioelectrical signals such as electrooculograms (EOGs) and electroencephalograms (EEGs) have many medical applications. Wet electrodes are used widely to acquire these signals; however, their use has several limitations. Other researchers have proposed dry contact electrodes, but they do not solve all of the problems associated with wet electrodes; on the other hand noncontact capacitive coupling electrodes have poor noise performance and are large and complex. In this paper, we present a hybrid electrode that is capable of both capacitive and resistive recordings at lower noise levels, with a smaller hardware footprint. The sensor was designed by optimizing the sensor input impedance value using a new electrode equivalent circuit that contained noise sources. Experiments were performed to investigate the frequency response, noise spectrum, motion artifacts, standard alpha and beta EEG signals, and eyelid and eyeball EOG measurements. We verified that our electrodes are capable of bioelectrical measurements at noise levels comparable to wet electrodes.

View full abstract

We developed a single unit proximity and tactile sensing method that simultaneously uses optical and electrical measurements. The proposed sensor consists of a pair of electrodes and a photodiode with a light emitting diode (LED). An increase in the electrode size is required in order to increase the sensitivity of electrical measurements. In addition, a smaller separation between the photodiodes is needed for high spatial resolution by optical measurement. In this paper, we proposed a structure that consists of a pair of electrodes and four pairs of photodiodes with LEDs for an array system. In the experiment, the identification of materials (grounded conductor or other materials), and detection of indentations on the sensor surface were demonstrated by a single sensor in contact and non-contact (proximity range). Furthermore, the prototype sensor array (3 × 3 units) measured the shape of the object. The proposed sensor may be useful as a tactile and proximity sensor for robots.

View full abstract

A new ion-balance/neutralizing current sensor for an AC corona ionizer was proposed and investigated by using a grounded ring electrode. Both the positive and the negative conduction currents can be measured independently using the proposed sensor. The sensor can cancel and eliminate the influence of the electric field from the emitter tip.

View full abstract

We have been conducting autonomous distributed MEMS research since the early 1990s. We are now working on an international project involving a new concept based on a self-movable and self-reconfigurable micro-conveyor utilizing ciliary-type micro-actuators arranged in an array over a large surface. The fabrication of the ciliary motion system (CMS) has been successfully simplified using photosensitive polyimides patterned by a direct UV lithography technique. The characteristics of the new device are equivalent to those of the previous devices made by classical methods, including plasma ashing. We also propose an integrated CMOS circuit to accurately regulate the input power of the thermal actuators while preventing overheating.

View full abstract

An improved gap-variable silicon nanowire waveguide coupler switch equipped with a micro actuator was designed and its wavelength characteristics were investigated. The coupler switch was assembled on a silicon-on-insulator wafer from an electrostatic comb-drive actuator and two submicron-scale freestanding single-mode waveguides. One waveguide was movable and the other was fixed. The movable waveguide was held by two supporting arms connected to the actuator. When a voltage is applied to the electrodes of the actuator, the gap between the waveguides reduces, allowing light travelling from the input waveguide to transfer to the output. The coupler was symmetrically shaped with respect to the center line between the waveguides to avoid asymmetric electromagnetic distribution. Port isolation of 18.5 dB was obtained at a wavelength of 1.55 µm, and the bandwidth over which the port isolation was higher than -10 dB was approximately 60 nm. These characteristics are suitable for a matrix switch in wavelength-division multiplexing.

View full abstract

High speed gas sensing devices can be applied in a number of areas where a better understanding of gas distribution is needed, such as in environmental monitoring and safety- and security-related fields. In this paper, we present a localized surface plasmon resonance (LSPR) sensor that was realized using sputtered Au and Ag nanoparticles (NPs), which can be used in robots for high-speed gas detection. The NPs' LSPR response, a red-shift of the minimum transmittance in wavelength (Δλ_min), and a decrease in the minimum transmittance (ΔT_min) for ethanol gas, were investigated and compared using Au and Ag NPs under the same sputtering conditions but using a different thermal annealing process for the reshaping of the NPs. The results obtained show that NPs with a larger aspect ratio can generate a large LSPR response. The response characteristics confirmed that this LSPR sensor can be used for high-speed gas detection.

View full abstract

This paper reports the development of a monolithic methanol concentration sensor for fuel cell applications. An interdigital capacitor and a resonator are fabricated on a single crystal quartz substrate. Methanol solution is introduced into a microchannel on the capacitor. The methanol concentration can be measured by measuring the frequency shift of the resonator because the shift shows a monotonic increase with a change in the relative permittivity of the capacitor connected in series to the resonator. The sensitivity is 0.1 wt %/Hz. We also found that the smallest resonator diameter that achieves a resolution of 0.1 wt % is 1.5 mm. Because the structure and manufacturing process are simple, we expect the proposed sensor to be useful for various kinds of liquid sensing applications.

View full abstract

We measured the electrical characteristics of DNA molecular bundles that were 25-µm long and had a diameter of 100-500 nm. We captured the bundle between the tips of silicon nanotweezers by dielectrophoresis. The two-terminal measurement, which used only the tweezers, failed because of the contact resistance between the bundle and the tips. We adopted a four-terminal measurement that eliminated the effect of the contact resistance. We fabricated potential measurement probes, which consisted of 2-µm-wide line electrodes with a 4-µm separation. The captured DNA bundle was pressed against the probes, and the potential drop associated with the current in the bundle was measured. We successfully determined the conductivity of the bundle.

View full abstract