Application fields and technical trends of wireless sensor network are surveyed. Progresses and subjects of sensor units, micro controller units, wireless communication units and power supply units which compose wireless sensor nodes are discussed. In order to deepen an understanding of practical use of wireless sensor network, “Smart Sensing Modules” which is currently under development are introduced as an example. The future of wireless sensor networks is also argued.

View full abstract

Bending motions of the tip of a conventional endoscope are controlled from outside the body by wire traction. A shaft of an endoscope should be relatively hard to avoid buckling by wire traction. The active bending mechanism of an endoscope, which is realized using shape memory alloy (SMA) coil actuators instead of wire traction, is soft. Using micro-fabrication technology on non-planar substrate, cylindrical substrate of thin endoscope was fabricated. These endoscopes enable precise observations and treatments of deep areas of the human body.

View full abstract

This paper describes design and fabrication of electromagnetically driven dual-axis tilting MEMS-grating, and evaluation for low coherent near infrared spectroscopy. At first, we have investigated fabrication of laminar grating using EB lithography of UV photoresist and dry etching of silicon. In consequence, the laminar gratings of 0.6 - 2.0μm pitches were fabricated successfully. Second, we fabricated electromagnetically driven MEMS-grating which can tilt to dual-axis. Primary axis is used for spectroscopy, and the secondary axis is used for optical axis alignment. As the results of evaluation, primary and secondary DC tilting angles were 0.40°/mA and 0.39°/mA, respectively. And then, primary and secondary resonant frequencies (Q-factor) were 217Hz (Q36) and 172Hz (Q25), respectively. Finally, we constructed Fourier domain fiber interferometer whose sample arm was 2m in length. As setting optical length difference to be 180μm, the interference spectrum in wavelength range of 1400-1700nm was observed in less than 25ms by MEMS-GR, and a Fourier and axis transformed peak was acquired at 50dB.

View full abstract

The hydrogen gas sensor using quartz resonators is developed to measure less than 4% hydrogen concentration in air. This sensor consists of two quartz resonators. Both sides of electrodes of the sensor resonator are made by platinum thin film. And the reference resonator has Au electrodes. By using this reference resonator, the influence of the temperature and pressure will be canceled. This sensor can measure hydrogen concentration from reaction heat on the platinum catalyst. From experimental results, the frequency of sensor changed linearly in 0% to 5% hydrogen concentrations mixed with the air. The sensor showed 20ppm frequency translation per 1%, and the time constant is about 20 seconds.

View full abstract

We have developed the etching technology using an ozone solution for chemically stable polymers such as polyimide, SU-8 and BCB, which are often used for MEMS, and a carbonized resist. Conventionally, these polymers are difficult to remove by O₂ plasma and organic solutions. In this study, the etching experiments of these chemically stable polymers were carried out using an acetic solution of ozone. The residues after the etching of the polymers were evaluated with surface profiler, scanning electron microscope and X-ray photoelectron spectroscopy. It was demonstrated that the acetic solution of ozone can etch and remove these polymers without residue. The developed method can remove not only organic polymers but also polymers containing inorganic materials, and is safe and easy.

View full abstract

A piezoelectrically excited micro cantilever with multiple electrode ports has been developed as a standard test device to investigate the piezoelectric oscillation sensing capability. A 5 μm thick PZT was deposited by the arc-discharge reactive ion plating on a 20-μm-thick and 2700-μm-long SOI cantilever, and its piezoelectrically measured vibration signal was correlated with the reference oscillation signal from the laser Doppler vibrometer to prove the feasibility as oscillation detector. An equivalent circuit expression for the sensing electrode has been found.

View full abstract

This paper reports a novel silicon bulk-micromachining process using deep reactive ion etching (DRIE) of silicon and electroplating of gold in order to realize a low-loss radio frequency (RF) waveguide. The waveguide developed in the handle wafer was electrically isolated by air, laterally actuated to close metal-to-metal contacts, and driven by an electrostatic actuator integrated on the SOI sides by the layer-separation technique. A thinned silicon-on-insulator (SOI) wafer of high-resistive handle layer and low-resistive active layer was chosen to meet the process and design requirements for a compact low loss switch.

View full abstract