Electromechanical analysis of a micromachined comb-drive actuator based on equivalent circuit method is described. From the equivalent circuit, we formulated electrical admittance for a comb-drive actuator as a function of AC driving frequency and derived some relation between specific frequencies which can be obtained by admittance measurement. We have also found that mechanical parameters of a comb-drive actuator such as spring constant, rigid mass and mechanical resistance could be estimated by the relation of the specific frequencies. Using this theory we evaluated mechanical properties of a fabricated comb-drive actuator and confirmed its practical usefulness for characterization of a comb-drive actuator.

View full abstract

In this paper, we propose a large-deflection electrostatic spiral-actuator with novel twisted-beams fabricated by surface micromachining. The stress-induced or bimetal-like actuators have merits of simple structure and fabrication steps with relatively large stroke. The novel stress-induced actuator presented here is composed of “twisted-beams", which have not only out-of-plane curvature but also rotation along its longitudinal direction. When the twisted-beams are used as components of a spiral actuator, the total stroke of the actuator becomes a sum of each deflection of the beams, and the stroke is much larger than conventional stressinduced spiral actuators. The experimental results of the spiral actuator show the maximum deflection of about 750 μm, which is extremely large for stress-induced-actuators.

View full abstract

A method for quantitative detection and discrimination of volatile sulfur compounds (VSCs) using an electrochemical sensor array combined with a preconcentrator was proposed. Halitosis is due to VSCs produced by bacterial metabolism inside the oral cavity. An organoleptic test is typically performed by a dental clinician for the assessment of halitosis, although it is a subjective test. Thus, an objective evaluation of halitosis is required. In this study, it was possible to discriminate among the VSCs such as hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), and dimethyl sulfide ((CH₃)₂S) over the range of 200ppb to 1000ppb. Moreover, mixture of two VSC vapors (H₂S and CH₃SH) at various mixing ratios were measured. The results indicated that the sensor responses to mixed samples satisfied the linear superposition. The mixture compositions of VSCs were almost correctly obtained from the sensor responses using partial least squares (PLS) regression analysis.

View full abstract

To develop a miniature complete blood count (CBC) analyzer for point-of-care testing (POCT), a MEMS CBC sensor based on the impedance method is discussed. A novel MEMS CBC sensor that is fabricated through a simple photolithography process using SU-8 is realized. However, the fabricated sensor exhibits a noisy output signal due to electrolysis gas. The relationship between the noise and the gas is revealed through microscopic observation and finite element method (FEM) simulation. To solve the problem of electrolysis gas, an improved MEMS CBC sensor with vanes is developed. The improved sensor is unaffected by electrolysis gas. Moreover, the signal stability of the sensor and the signals detected for latex particles are successfully evaluated.

View full abstract

Actuators that have a large driving force are necessary for use in micropumps and microvalves. These are produced by using PZT bulk ceramics having excellent piezoelectric properties together with Si single crystal. A novel fabrication process was proposed for bulk PZT microactuators. This process was composed with bonding a bulk PZT to a Si wafer, thinning the PZT down to several ten microns in thickness after bonding, micromachining of the thin PZT by an excimer laser, and Si micromachining such as reactive ion etching and anisotropic wet etching. A PZT-Si diaphragm structure was fabricated by this process, and successful operation of the diaphragm actuator was demonstrated.

View full abstract

We propose the design, simulation and preliminary fabrication of Micro Conveyer Systems (MCS) based on polymer electrostatic comb-drive actuators using polymethylmethacrylate (PMMA). This MCS consists of linear comb actuators, rotational comb actuators, micro containers, and a ratchet mechanism. Micro containers, used for carrying micro and nano samples such as protein, cells, are moved by comb-actuators through the ratchet mechanism. The silicon MCS was fabricated and checked to confirm characteristics and working principles. Each PMMA MCS, which has dimension of 1x1cm², will be fabricated by using hot embossing technique or X-ray lithography. A silicon mold has to be fabricated first by using silicon wafer and ICP-RIE process. Salient advantages of PMMA comb-drive actuators are low cost, high throughput and consuming less energy compared with the counterpart using silicon because PMMA has a lower Young's modulus.

View full abstract

Temperature stability is one of the major concerns of sensors for practical applications. This paper presents a method for improving the temperature stability of CMOS magnetic rotary encoders. The main factor of the offset drift is the piezo-resistive effect due to the stress induced by packaging. A connection of four MAGFET elements offers a good offset drift cancellation capability while keeping the sensitivity. Using the proposed method, the offset drift is reduced from 0.4 % without the cancellation to 0.15 % with cancellation under the temperature range of 5°C to 80°C.

View full abstract

This paper presents the design and implementation of a one-chip camera device for capsule endoscopes. This experimental chip integrates functional circuits required for capsule endoscopes and digital image transmission function. The integrated functional blocks include an image array, a timing generator, a clock generator, a voltage regulator, a 10b cyclic A/D converter, and a BPSK modulator. It can be operated autonomously with 3 pins (VDD, GND, and DATAOUT).
A prototype image sensor chip which has 320x240 effective pixels was fabricated using 0.25μm CMOS image sensor process and the autonomous imaging was demonstrated. The chip size is 4.84mmx4.34mm. With a 2.0 V power supply, the analog part consumes 950μW and the total power consumption at 2 frames per second (fps) is 2.6mW. Error-free image transmission over a distance of 48cm at 2.5Mbps corresponding to 2fps has been succeeded with inductive coupling.

View full abstract

Recently, MEMS devices are being studied for which the focus can be changed by moving a lens. Therefore, we propose a MEMS-based varifocal mirror in which piezoelectric actuators are used. In this study, we used micromachining to fabricate a varifocal mirror by bonding bulk PZT to Si single crystals, and then evaluated its performance.

View full abstract

In this paper, we investigate an influence of Fresnel diffraction to the Plane-pattern to Cross-section Transfer (PCT) technique. An analysis was performed by considering the X-ray intensity distribution. The mask pattern employed in this work was a set of right triangles placed in double rows facing each other. The design is based on the fact that when mask slit becomes narrow as it approaches the corner, the influence of the diffraction gradually becomes more significant. In X-ray lithography in optical applications, it has been realized that the Fresnel diffraction is an important factor for designing the shape of slits in submicron. The triangle mask pattern has a pitch of 1.48 μm and a height of 20 μm with Ta absorber thickness of 0.5 μm. Using PCT technique, the analysis was summarized by comparing Fresnel diffraction simulations and the data from experimental results. This work has proved that a submicron structure fabrication by PCT is possible with proximity gap of at least 200 μm.

View full abstract

Diamond thin films fabricated by MPCVD (microwave plasma chemical vapor deposition) are available for use as a field emitter material, because of its high mechanical quality, thermal conductivity, chemical stability, environmental tolerance, and NEA (negative electron affinity). Diode and triode emitter arrays using P-doped polycrystalline diamond were manufactured on a SiO₂/Si(100) substrate with reverse pyramids formed by the transfer mold technique. As the diamond nucleation process, spin-coat seeding with pure diamond powder dispersed in isoamyl acetate has been introduced in place of the bias method. SEM (scanning electron microscopy) images and Raman spectroscopy indicate that the crystal quality of the diamond thin film fabricated by spin-coat seeding is superior to that fabricated by the bias method. The diamond crystal completely grew on top of the diode emitter by the US (ultrasonic) treatment in a diamond powder solution before spin-coat seeding. The tip radius was smaller than 50 nm. The beginning voltage of the emission of the diode emitter is 3 V after the DC glow discharge treatment in H₂, which is lower than that of an emitter array fabricated by the bias method, 40 V. On the other hand, the emission of the diamond triode emitter starts at a gate voltage of only 0.5 V, and the emission current of 50∼60 mA is obtained at a gate voltage of 2 V.

View full abstract

Bulk BPSCCO (Bi-Pb-Sr-Ca-Cu-O) as a magnetic sensor was fabricated by use of the shock compaction technique, and then annealed under a temperature of 845 °C for 48 hours in an electronic furnace. The magnetic sensitivity S of the specimen was about 13 %/(10^-4 T) over the range of measurement of the magnetic field B_meas from 0 to ±5×10^-4 T, under a constant 40×10^-4 T of the B_bias values. This was approximately 13 times greater than that of GMR (giant magnetoresistance) sensor. It was determined it was possible to apply the bulk BPSCCO specimen as a highly sensitive magnetic sensor. The present paper demonstrates the dependence of resistance R(T), without the application of a B_bias, for the specimen on temperature, the dependence of resistivity ρ on the current density J, the dependence of the magnetic sensitivity S on ρ, and the dependence of the R_meas on B_meas. In addition, the present paper compares the characteristics of magnetic sensors constructed with and without the shock compaction method and discusses the results.

View full abstract

This paper studies the average-irradiance dependence in the frequency response of the three-phase correlation image sensor (3PCIS). For the ac component of the photocurrent, a small-signal equivalent circuit of the 3PCIS pixel is derived. Based on this circuit, it is found that, for each fixed modulation frequency, the transfer function of the ac photocurrent from the photodiode to the NMOS multiplier transistors is formulated as a negative-phase high-pass filter in terms of the dc photocurrent, which is proportional to the average irradiance. A method is then proposed that compensates the irradiance-dependent frequency response by inverse filtering pixel by pixel. In experiments, the irradiance dependence in the frequency response of a 64×64-pixel 3PCIS chip is measured and analyzed to estimate a key parameter. By using the estimated parameter, the output images of the 3PCIS are successfully compensated for the irradiance-dependent frequency response, with the phase error being less than 1° up to 5 kHz modulation.

View full abstract

We have designed two kinds of cantilever MEMS switches based on two-stage driving. These micro-switches can mitigate tip-first-touching of the contact part and expected to have a long lifetime. Moreover, the driving voltage is low while keeping the device miniaturization. The RF characteristics of insertion loss and isolation are calculated and shown to be excellent. The micro-switches are fabricated by silicon deep dry etching using an SOI wafer and then electrostatic bonding onto a glass substrate. This process is fairly simple and confirmed to be able to fabricate two electrode gaps precisely.

View full abstract

A concentrator chip which could detect a variety of heavy-metal ions was fabricated. To improve the detection sensitivity, a droplet of a sample solution was concentrated evaporatively using a super-hydrophobic surface formed with polytetrafluoroethylene (PTFE) beads. The system consists of a working electrode at the center, surrounded by an Ag/AgCl reference electrode. Square-wave anodic stripping voltammetry was conducted using concentrator chips with different working electrode materials. A significant increase in peak height was observed as the sensitive area decreased and the volume of the droplet increased. When a 5-μl droplet was used, the detection limit for lead, cadmium, and arsenic ions was 1 ppb.

View full abstract

In this paper,sensor response by film material was described. Multi detecting film and multi metal electrodes were also examined. Film material was changed from the Di Octadecyl Dimethyl Ammonium Bromide to Tri Octadecyl Amine Hydro Chloride. To detect five basic taste substances, sensor parameters were defined by maximum voltage change and response time. Using these parameters, discrimination possibility of five basic taste substances were shown.

View full abstract

The remarkable negative photo-induced current and negative differential characteristics according to the forward bias voltage have been observed successfully for GaAs/GaAlAs multi-quantum well structures with a storage layer of InAs/GaAs short period superlattice. The characteristics are dependent on the crystal quality of the storage layer and extremely enhanced by using the InAs/GaAs short period superlattice compared with In_xGa_1-xAs alloys.

View full abstract

Plant can recognize the environmental factors, for example temperature, humidity, atmospheric pressure and light intensity. Humans can identify the capabilities by measuring the plant bioelectrical potential. It can also recognize the breezing wind. Plants can be regarded as an environmental sensor by using the potential. In this study, the bioelectrical potential characteristic to the wind grade was examined. As for the results, the correlation between the characteristic and the grade was derived. The correlation coefficient was very high. The integrated value for the potential was adopted to derive the relation. Plant can identify the wind intensity by adopting the value. It became obvious that plant has higher capabilities to sense the environmental factors not only temperature, humidity and light intensity but also wind intensity. The application field of plant will spread by using these results.

View full abstract

References(6) Wrong:Two-photon-absorbed near-Infrared photopolymerization for three-dimensional microfabrication
Right:Force-Controllable, Optically Driven Micromachines Fabricated by Single-Step Two-Photon Micro stereolithography

View full abstract

picture Wrong:
Right:

View full abstract