Quality factor of micro cantilevers transduced by piezoelectric lead zirconate titanate film

The quality factors (Q-factor) of micro cantilevers transduced by piezoelectric lead zirconate titanate (PZT) film under atmospheric pressure conditions were investigated and discussed. It was found that Q-factors increased with thicker PZT film. Due to air damping, shorter cantilevers resulted in preferred larger Q-factors. The Q-factor was found to be as high as 450 for a 150-μm long PZT cantilever when using 1.04-μm thick PZT film as the electromechanical conversion medium. Differences in the measured Q-factors when using integrated PZT film self-excitation and external PZT vibrator actuation indicate that energy dissipation induced by the electromechanical coupling in PZT thin films was noteworthy even under atmospheric pressure conditions. Moreover, the mechanical properties of the PZT film were found contribute significantly to decreases of the Q-factor.     

Effect of double air injection on performance characteristics of centrifugal compressor

In the operation of a centrifugal compressor of turbocharger, instability phenomena such as rotating stall and surge are induced at a lower flow rate close to the maximum pressure ratio. In this study, the compressed air at the exit of centrifugal compressor was re-circulated and injected to the impeller inlet by using two injection nozzles in order to suppress the surge phenomenon. The most effective circumferential position was examined to reduce the flow rate at the surge inception. Moreover, the influences of the injection on the fluctuating property of the flow field before and after the surge inception were investigated by examining the frequency of static pressure fluctuation on the wall surface and visualizing the compressor wall surface by oil-film visualization technique.     

Large area micro hot embossing of Pyrex glass with GC mold machined by dicing

Micro/Nano imprinting or hot embossing is currently a target of interest for industrial production of micro and Nano devices for the low cost aspect. In Fluidic MEMS (Micro Electromechanical Systems) applications, polymer materials have been widely employed for their low cost to fabricate the economical products (Becker and Heim in Sens Acuators A 83:120–135, 2000; Becker and Gaertner in Mol Biotechnol 82:89–99, 2001). However glasses are much more suitable for the higher temperature applications or under the stronger chemical environments. Moreover UV absorption of glass materials is much less than that of polymers, which is the advantage for bio-analysis. In Optical MEMS as well, glasses are good candidate materials for the better optical properties, such as high refractive index, low UV absorption and others. Although wet etching of glasses is widely employed for fabrication of fluidic MEMS devices, the wet etching is not satisfactory for the low machining resolution, the isotropic etched profile and poor roughness of the fabricated structures. Dry etching of glasses is then an alternative for Micro/Nano structuring, but the etching rate is extremely low (order of 0.1 μm/min) and the cost is too high because of the expensive RIE (Reactive Ion Etching) facility. Above mentioned is the reason why we are interested in hot embossing or imprinting of glasses of Micro/Nano scale. In our previous study, Micro/Nano imprinting was developed for Pyrex glasses using GC (Glassy Carbon) mold prepared by FIB machining (Takahashi et al. in Symposium on DTIP 2004 pp 441–446, 2004). The disadvantage of FIB machining is limited area of etching. The typical area of FIB is less than several hundreds micrometer square. This is the reason why we tried the large area of embossing using GC mold fabricated by dicing machine. Micro hot embossed test structures were successfully demonstrated with good fidelity. Fabricated micro structures can be applied for fabrication of microchamber array for PCR (Akagi et al. in Sci Techol Adv Mater 5:343–349, 2004; Nagai et al. in Anal Chem 73:1043–1047, 2001).     

Compact Radiation Shield for a Superconducting Array Molecule Detector

Recent development on large-scale superconducting array detectors requires a large through hole along the molecular flight path in a cryostat. The through hole causes degradation of detector performance due to the 300 K radiation and a short holding time at the cryostat base temperature. To realize a compact detector system, we designed and fabricated infrared radiation shields with a fine-honeycomb collimator and a micro-structured metal-mesh. The infrared flux through the honeycomb collimator located at 50 K was 300–500 μW. A test run in a cryostat showed a holding time of 8 hours. We fabricated a metal-mesh consisting of a self standing Cr/Cu film with an array of 2.0 μm holes having a pitch of 3.5 μm. The metal-mesh was supported by a Si reinforce structure. Spectral measurement indicates that the transmission of the 300 K radiation is less than 1%.      

Delayed hepatic signal recovery on ferucarbotran-enhanced magnetic resonance images: an experimental study in rat livers with gadolinium chloride-induced Kupffer cell damage

Objective

Hepatic signal recovery, rather than reduction, in ferucarbotran-enhanced magnetic resonance imaging (MRI) is a potential diagnostic marker of liver damage. We investigated hepatic signal recovery in rats with gadolinium chloride (GdCl₃)-induced Kupffer cell (KC) damage.

Materials and methods

Twelve rats received 8 μmol iron/kg of ferucarbotran 1 day after 0–7.5 mg/kg GdCl₃ injection (experiment A). Another 12 rats received ferucarbotran followed by GdCl₃ injection 6 h later (experiment B). In each experiment, three rats without GdCl₃ (“no injury group”) served as control. Another six rats received GdCl₃ alone without ferucarbotran. Hepatic signals were assessed on T ₂ ^* -weighted images for up to 29 days. Iron deposits were histologically examined on day 29.

Results

Hepatic signal recovery was delayed in a GdCl₃ dose-dependent manner in experiment A. Gadolinium chloride alone reduced hepatic signal 15 % during this experiment. Hepatic signal recovery was delayed only in rats that received 7.5 mg/kg GdCl₃ in experiment B. Hepatic signals negatively correlated with iron deposits in KCs and hepatocytes.

Conclusion

Hepatic signal recovery on ferucarbotran-enhanced MRI was delayed in the context of GdCl₃-induced KC damage due to increased hepatic iron deposits. Hepatic signal recovery may be used as a clinical marker of KC damage in liver disorders, including radiation-induced hepatitis.     

A replication process of metallic micro-mold by using parylene embossing and electroplating

This study demonstrated a replication process for metallic micro-mold that combines the parylene-C (poly-chloro-p-xylylene C) hot-embossing and electroplating techniques. A nickel original master was fabricated using the deep RIE silicon etching followed by the electroplating process. Then, the patterned fields composed of arrays of 25 μm-high, 10 μm-wide and 1 mm-long lines with 10 μm spacing in nickel molds were successfully replicated on the 60 μm-thick parylene-C films by the hot-emboss process. Under complete filling conditions, the deviation of the replicated micropattern was less than 2.4%. The electroplated copper successfully filled parylene-C replica master patterns with the aspect ratio of 2.5 without the void formation by both adding organic addictives and controlling the seed layer thickness. After electroplating, the copper micro-mold could be successfully separated from the parylene-C replica master.     

Microstructuring of SU-8 photoresist by UV-assisted thermal imprinting with non-transparent mold

In this study, we explored a rapid and low-cost process for patterning in a SU-8 photoresist by thermal imprinting with a non-transparent mold such as Ni mold. One of major obstacles in the process is that the extremely good formability of uncured SU-8 even near room temperature causes the collapse of imprinted patterns during and after de-molding because a sample cannot be exposed to UV light during imprinting owing to the non-transparency of a mold. To overcome this problem, un-cured SU-8 resists were pre-treated with UV light, heat, and O₂ plasma for controlling their formability, and applied to thermal imprint tests to be compared each other in terms of the replication fidelity. As a result, a SU-8 sample pre-treated with UV light for 8 s resulted in the best replication quality for given imprint conditions and mold dimensions, and we could successfully replicate micro patterns in SU-8 resist without a quartz mold. As compared with conventional UV-imprint processes, this process has potential merits such as a lower mold cost, an easier mold release and a less air-entrapment.     

Passive piezoelectric DC sensor applicable to one-wire or two-wire DC electric appliances for end-use monitoring of DC power supply

A passive, non-contact piezoelectric DC electric current sensor to satisfy the increasing needs of DC power supply for monitoring the electricity consumption by either one-wire or two-wire appliance cord was proposed, and the sensing principle was schematically described and experimentally verified. A micro magnet was integrated into the proposed DC sensor and the appropriate position for locating the micro magnet was theoretically pinpointed. A prototype DC sensor was fabricated, and an impulse piezoelectric voltage output was detected when a DC electric current was applied to a two-wire electrical appliance cord, by using the constructed measurement setup for demonstration. A linear relationship between the detected peak value of the impulse output voltage and the applied DC electric current was further obtained based on the empirical measurements. In light of the above preliminary results, the proposed piezoelectric DC sensor is thus believed to be useful to various kinds of DC electricity end-use monitoring systems without consuming power electricity and using cord separators even in the case of the two-wire appliances.