Aiming at the use in low-invasive medical treatments, this paper reports a fabrication of metallic microneedle, which has a three-dimensionally sharp tip. Compared to a silicon or polymer needle which we previously proposed, a metallic needle has toughness to evade breakage. Even if it is broken, it does not become small pieces thanks to its ductility, which increases the safety for a human body. A nickel needle was fabricated using electroplating, followed by sharpening it by electrochemical etching. A smooth tip surface is obtained due to electrochemical etching reactions. Sharpness and smoothness of the tip are effective for easy insertion in the viewpoint of large stress concentration and small friction, respectively. An experiment of inserting the fabricated needle into an artificial skin of silicone rubber was carried out. The resistance force during insertion was much reduced compared to that of commercial stainless needle (23 G: shank diameter 650 µm). Although a fabricated metallic needle was inserted and pulled-out for several times, it was not broken in any trial. By changing the angle between object surface and needle axis, the insertion experiments were carried out. Fabricated nickel needle was not broken for any angle, while silicon needle was broken in case the angle is small, i.e., the needle is much inclined from normal direction of the surface, which ensures the safety of metallic microneedle to human body in the viewpoint of breakage.

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The high-speed, rotational scanning of laser beam was applied to the pipe inner wall inspection system that measures the cross-sectional shape of the pipes based on triangulation. The system is mainly composed of the laser diode (LD) and a position sensitive device (PSD) that goes through inside the pipe to obtain three-dimensional cross-sectional image. Since the reflectivity of the light from LD varies with pipe's inner conditions, simultaneous control of the PSD's receiving light level and the LD light maximum intensity is required for accurate measurement and the LD protection. Moreover, high-speed responding of the control is essential for time-effective inspection. Therefore, we designed an analog circuit that has two feedback loops in this study. One is to keep the PSD's receiving light intensity at a constant level and the second is to keep the maximum output of LD lower than the maximum ratings by feeding back the output of built-in photodiode of the LD.
We experimentally showed that the proposed control system keeps the receiving light amount of the PSD at a constant level against a sudden reflectivity change by about 15 times.

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A variable capacitor with high capacitance ratio (C_R) is strongly expected as one of the key devices to realize controllable/ reconfigurable filters for multi-function, multi-band wireless systems. The authors have developed a fluid MEMS capacitor technology as one of the promising candidates for achieving high C_R and have reported the excellent microwave performance. In order to verify such technology from a practical viewpoint, the change in the capacitor performance over time was studied, and found out the method to suppress the drift phenomenon.

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Shunt-type MEMS resistive switches perform low loss and high isolation in a wide frequency band. However, they suffer from a high driving voltage similar to other MEMS electrostatically-driven switches. The decrease of the gap between the driving electrodes causes stronger electrostatic force, leading to the driving voltage decrease. On the other hand, the reduction of the gap causes another problem, e.g. decreasing the isolation. In this paper, in order to investigate the influence of the gap reduction on the performance of the MEMS switches, we fabricated a switch with the gap of 0.9 μm and compared it with one having the gap of 2 μm. The measured results have showed that the fabricated narrow gap switches have as good RF frequency characteristics as the 2 μm gap ones, owing to forming a slit in the moving electrode over the transmission line.

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We developed a new oil leakage sensor using blue-violet excitation light modulated with amplitude shift keying (ASK). The sensor can selectively detect fluorescence from insulating oil or turbine oil without being affected by ambient light.

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