This paper reports a bicone-shaped micro coil that has a low resistance and a low parasitic capacitance for magnetic resonance imaging (MRI). The micro coil was fabricated by vacuum evaporation and electroplating of copper (Cu) onto a stepped helical structure developed by a three-dimensional (3D) printer. Because the stepped helical structure was fixed on a rotary-tilted stage, Cu was evaporated only on the coil wiring part of the helical structure. Unlike for the folding method, a micro coil developed by vacuum evaporation could be fabricated even if there were lines that overlapped between the coil wirings. Furthermore, the resistance of the coil could be decreased by electroplating, and by increasing the linewidth of the coil wiring that was fabricated by the 3D printer. By using the fabricated bicone-shaped coil, high signal-to-noise ratio (SNR) MRI images could be obtained. In conclusion, a higher SNR MRI image can be obtained by increasing the linewidth and decreasing the resistance.

Stacked piezoelectric actuators are often embedded in magnification mechanisms. Residual vibration frequently deteriorates positioning performance. The authors have proposed a driving method of a piezoelectric actuator using current pulses for high resolution, hysteresis reduction, and good linearity. This paper evaluates the reduction of residual vibration using a current pulse drive with adjustment of pulse patterns dictated by a genetic algorithm. The pulses from the source and the sink were counted as positive and negative, respectively. The displacement was estimated using a simulation based on Martin's model for optimized current pulse intervals. The current pulse drive was compared with the voltage drive by input shaping. Although the residual vibrations were almost the same for both current pulse drive and input shaping voltage drive in the simulations, current pulse drive resulted in smaller vibrations in the experiments. The residual vibration in the higher harmonics was observed in the input shaping drive because no harmonics were considered in the simulation model. The integral of the current pulse decreased the higher frequency components. Then, the higher harmonics were decreased.

A moisture-in-oil sensor, with a sandwich structure of Cr nanoporous thin film/polyimide film/Au electrode, was fabricated using a lithographic process, sputter deposition, and chemical dealloying. One of the Cr nanoporous thin films used as a molecular filter was made using oblique incidence film formation and sputter deposition at 2.5 Pa of argon and a 60 degree attaching angle. The fabricated Cr nanoporous thin film consisted of 30-50 nm pore sizes as a result of a “shadowing effect”. A moisture-in-oil sensor made with this Cr nanoporous thin film showed favorable responsiveness in oil, with a response time of about 7 minutes, well within the desired maximum value of 10 minutes. To further improve the responsiveness of the sensor, another Cr nanoporous thin film was prepared using a chemical dealloying process, which facilitates control of the pore sizes. This process consists of co-sputtering Cu and Cr, annealing for 1 h at 573 K and dealloying for 15 h in 32.5% HNO₃. The thin film pore sizes depend on the initial Cu-Cr compositions, which were researched using a combinatorial technique at various fabrication conditions. We investigated a wide compositional range between 32 and 22 at.% Cr. It was found that between 28 and 22 at.% Cr, chemical dealloying results in low residual Cu, less than 10 at.%. The pore sizes obtained were <20 nm for 32 at.% Cr, 20-40 nm for 28 at.% Cr, 40-60 nm for 25 at.% Cr and >60 nm for 22 at.% Cr. The initial composition ratio of 28 at.% Cr was used to fabricate a Cr nanoporous electrode film filter for a moisture sensor. Unfortunately, the final residual Cu composition ratio was 17 at.%, which is more than the desired maximum of 10 at.%, because the thin film had a uniform composition. The changes in the electrostatic capacity of the moisture sensor as a function of relative humidity (50%RH-90%RH) in air were studied, and the sensor output followed changes in the relative humidity.

We report on a novel design of a complementary metal oxide semiconductor microelectromechanical system (CMOS-MEMS) multilayer infrared (IR) emitter based on Central Semiconductor Manufacturing Corporation (CSMC) 0.18-µm 1-Poly-6-Metal (1P6M) CMOS technology. The locations of the electromechanical contact points are optimized on the IR emitter plate to enhance the thermal conduction, thereby improving the response speed to at least 1.6 kHz. The double-deck structures of the MEMS IR emitter suspended over integrated circuits have compatibility with the post-CMOS processes, which is beneficial to develop IR emitters of a high fill-factor and a high radiance. In the emitter plate, a 1.4 kΩ heating resistor is composed of tungsten via chains to make the working current for the emitter as low as possible. A possible post-CMOS MEMS process is proposed without any violation of design rules, thus maintaining the compatibility with most CMOS technologies. Finally, the enhancement of the operation speed is verified using a simulation of the thermal radiation properties of microemitters with the optimized contact locations.

A calorimetric determination of protein concentration for a picoliter (pL) liquid sample is proposed using a microfluidic calorimeter on a thermally isolated membrane. The concentration measurement of cytochrome c in a pL solution based on an AC calorimeter by the absorbance of a 532 nm diode laser is demonstrated to monitor the temperature change of the microchannel. The resolution of the concentration is defined by measuring the temperature change against various concentrations. In the case of the fabricated micro-calorimeter, the heat resistance of the isolated membrane is obtained as 1579 K/W. The composed heat resistance, including the support membrane and the solution in the channel, is obtained as 118 K/W. Although the heat loss is extensive, the resolution is calculated as 3.3 mM as a concentration sensor with 1.5 mol/K sensitivity. The calorimetric device has more potential to be used for detection of extremely small concentrations in liquid by optimizing the thermal isolation with a higher concentration resolution.

This paper describes an improved particle-excitation flow-control valve with high flow rate and controllability. The proposed control valve has a small volume, is lightweight, and can smoothly control the airflow through particle excitation. Pneumatic actuators, which have many advantages, are widely used in automation machine equipment and are expected to be used in robots. In general, such highly controllable pneumatic-control devices used as proportional valves are large-scale, heavy, and exhibit low response. We have developed a new flow-control valve called a particle-excitation flow-control valve, which has a simple structure with a lead zirconium titanate (PZT) resonance mode, large control-flow rate, and is lightweight. Further, this valve is expected to be highly responsive because it is driven by a PZT vibrator. In this study, we designed an experimental prototype to increase the maximum flow rate and measured its flow control and response characteristics. Moreover, we showed that this control valve has high controllability and control flow rate.

An ex vivo brain lactic acid (LA) monitoring system for investigating brain activity at the organ level was constructed and tested in continuous LA monitoring. Our system consists of a micro-fluidic dual-analyte (LA and glucose) biosensor and a special brain chamber that is suitable for organ level experiments. The biosensor utilizes the redox reactions of osmium-wired horseradish peroxidase (Os-HRP) to detect hydrogen peroxide produced by enzyme reactions. The sensor had sufficient sensitivity (LA: ∼ 0.01 mM, glucose: ∼ 0.01 mM) and selectivity for assessment of extracellular LA. The ex vivo monitoring of brain LA was performed using the proposed system. As a result, the change in extracellular LA was successfully monitored continuously, and the change in the LA level was considered the result of metabolic activity of the sample. Our system is expected to be useful not only for ex vivo brain monitoring, but also for monitoring other organs.

UV curing makes photoresists inactive to additional UV exposure and is applied to generate a fine outline pattern from a wider original mask pattern. Using the standard g-line photoresist, a roughly 1-µm-wide pattern is produced. The final pattern is a UV-cured photoresist that does not remain on the other material, suggesting few limitations on applications.

Insulator and piezoelectric thin films were deposited on titanium substrate, and characterized for application in tough MEMS tactile sensors. The titanium substrate was polished by buffing before the deposition of the thin films. An Al₂O₃ thin film was deposited as an insulator and showed good insulation characteristics on the polished titanium substrate. Piezoelectric BiFeO₃ thin films were prepared by RF sputtering. The XRD pattern of the BiFeO₃ thin film on the titanium substrate shows the presence of the ferroelectric phase. The polarization-electric field curve also shows a ferroelectric hysteresis loop. The results show that insulator and piezoelectric thin film can be formed on titanium substrate.