Lubricants such as engine oil play an important role in preventing machine wear and damage. Monitoring the deterioration of lubricating oils is a significant technical issue in machine maintenance. In this study, a sensor for monitoring engine oil viscosity was developed using a metal-core piezoelectric fiber/aluminum composite. This composite is a piezoelectric ceramic that is reinforced by a metal matrix; it is expected to be utilized in harsh environments such as the inside of an engine. An active type measurement method was employed to monitor variations in the viscosity of glycerin solution as a model liquid. In this method, a self-generated vibration is correlated to the viscosity of a liquid by measuring the damped vibration amplitude and the variation in the resonance frequency. The results showed that the vibration had a high sensitivity to the liquid viscosity; further, it was observed that the shift in resonance frequency correlated to a wider range of measurable viscosity. Both measured parameters indicate that the metal-core piezoelectric fiber/aluminum composite is a viable sensor for engine oil monitoring.

The temperature dependence of the resistivity $\rho \mathrm{}\left(T\right)\mathrm{}$ and the thermoelectric power $\alpha \mathrm{}\left(T\right)\mathrm{}$ have been measured under hydrostatic pressure on a single-crystal film of ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_4$ deposited on a ${\mathrm{LaSrAlO}}_4$ substrate. The compressive biaxial stress built into the film raises $T_c$ at ambient pressure. $T_c$ increased with pressure $P<\mathrm{}3.3\mathrm{}$ kbar, but saturated at a pressure-independent $T_c=43.7\mathrm{}$ at pressures $P>\mathrm{}3.3\mathrm{}$ kbar. A low-temperature enhancement of $\alpha \mathrm{}\left(T\right)\mathrm{}$ having a $T_{\max }\approx 140$ K increased with $T_c.$ The data are discussed within the framework of a vibronic model of the superconductive phase.

P-type nanocrystalline Bi_0.4Sb_1.6Te₃ thick films were directly deposited on copper substrates by aerosol deposition (AD) involving shock compaction of the starting powder at room temperature. The film deposition rate was over 700 μm/min. The relative density of the films was above 95%. Films with a thickness of over 2 mm were obtained. They consisted of nanocrystals with grain sizes of several tens of nanometers. The crystal structure of the films was the same as the bulk materials prepared by spark plasma sintering (SPS) using the same starting powder. We measured the electrical conductivity, carrier concentration, Hall mobility, and thermal conductivity of the films and compared them with those of the bulk materials. The thermal conductivity of the AD film was 20-30% lower than that of the bulk materials, which is attributed to the increased number of grain boundaries and some defects in the AD films.

It is well known that the curing residual stress induced during a fabrication process has a great influence on the performance of piezoelectric composite devices. The purpose of this work was to evaluate the residual thermal stress of lead zirconate titanate piezoelectric fiber aluminum (Al) matrix (piezoelectric fiber/Al) composites generated during fabrication numerically and experimentally and to understand the effect of the residual thermal stress on the electromechanical response. The three-dimensional finite element method was employed, and the residual stress generated during the solidification process of the Al matrix was calculated. The output voltage was also calculated in the analysis when putting stresses on the composite materials in the length direction of the piezoelectric fiber. It was shown that the cooling from higher temperatures increases the electromechanical conversion capability. Furthermore, we also performed the simulation, and we recorded the output voltage under concentrated load to investigate its application as a load position detection sensor, and we also discussed the influence of the position by changing the modeling with a different fiber position in the Al. The residual stress of hot press molded piezoelectric fiber/Al composite was then measured, and the comparison was made with the calculated values. The simulation results revealed that our model predictions reproduced and explained the experimental observations of curing residual stress. After this study, similar models of composite materials can be analyzed by this simulation, and the result can be used to design piezoelectric composite materials.

Natural cellular activities are increasingly exploited for micro analytical systems, biochemical reactors. We have proposed novel use of pulsating heart cells as mechanical micro actuators. Here we propose a novel bio-actuated power generator combined with the contractile force of heart muscle cells and piezoelectric fiber as a material of vibration energy conversion into electrical energy. Their beating frequency is about 1~2 Hz, so they heartbeat about 1.0times10 ⁶ times a day. We expect our proposed power generator to convert this vibration energy into the electrical energy with a piezoelectric fiber, which is widely used as an electromechanical transducer. The advantage of this living actuator and power generator, such as a heart muscle cell, is a self-organized, self-repaired and chemical energy driven mechanical component without electrical energy supply. They convert chemical energy into kinetic energy efficiently and heartbeat themselves autonomously. In this paper, preliminary experiments have been demonstrated and its principle and prototype device have been shown.