Hidenori Katsumura

The Power Generation Characteristics and Durability of a Vibration Power Generation Device using Piezoelectric Thick Film Formed Directly by Screen Printing on a Stainless Steel Substrate

This paper presents a small, high-performance and novel device that generates power from vibrations, made using screen-printing to form a piezoelectric thick film directly on a stainless steel substrate. This simple and cheap method realizes a 20 – 40 μm-thick piezoelectric film, otherwise difficult to achieve using thin-film techniques or ceramic sintering, on a stainless steel substrate. A maximum output power of 1.1 mW was recorded with acceleration of 0.1 G0p (0.98 ms−2) applied at a resonance frequency of 24 Hz. We also evaluated the durability of the device by repeatedly striking the tip of the element. Output power exceeding 100 mW under damped resonant vibration was generated at the instant of striking, with approximately 0.9 mJ of power measured per single damped vibration. No deterioration was seen in the integrity of the stainless steel substrate or the piezoelectric thick film after over 10 million strikes.

Preparation and Characterization of Low Temperature Sintered Alumina by CuO-TiO2-Nb2O5-Ag2O Additives

For the purpose of enabling the low-temperature sintering of alumina, the addition of Ag 2 O to CuO-TiO 2 -Nb 2 O 5 type sintering additive was examined. The use of CuO-TiO 2 -Nb 2 O 5 -Ag 2 O type sintering additive by 5 wt% enabled the low-temperature sintering of alumina at 860°C. It is presumed that the formation of Cu 4 TiNb 4 O x solid solution has an important role for low temperature sintering of alumina. The obtained sintered material showed high thermal conductivity of 18 W/mK, higher than that of conventional LTCC materials, and that the material could be co-fired with silver electrodes.

Low Temperature Sintering of Alumina by CuO-TiO2-Nb2O5 Additives

We examined sintering additives for alumina. When using CuO-TiO2-Nb2O5 additive, dense sintered alumina was obtained by firing at 1000°C or below, even though additive content was at most 10 mass%. It is considered that the formation of mixed oxide consists of CuO, TiO2 and Nb2O5 has an important role for low temperature sintering of alumina. Thermal conductivity of the above sample was 15 W/mK, which was the highest value yet reported within LTCC (Low Temperature Co-fired Ceramics) materials.

Wideband piezoelectric energy harvester for low-frequency application with plucking mechanism

Wireless sensor networks need energy harvesting from vibrational environment for their power supply. The conventional resonance type vibration energy harvesters, however, are not always effective for low frequency application. The purpose of this paper is to propose a high efficiency energy harvester for low frequency application by utilizing plucking and SSHI techniques, and to investigate the effects of applying those techniques in terms of the energy harvesting efficiency. First, we derived an approximate formulation of energy harvesting efficiency of the plucking device by theoretical analysis. Next, it was confirmed that the improved efficiency agreed with numerical and experimental results. Also, a parallel SSHI, a switching circuit technique to improve the performance of the harvester was introduced and examined by numerical simulations and experiments. Contrary to the simulated results in which the efficiency was improved from 13.1% to 22.6% by introducing the SSHI circuit, the efficiency obtained in the experiment was only 7.43%. This would due to the internal resistance of the inductors and photo MOS relays on the switching circuit and the simulation including this factor revealed large negative influence of it. This result suggested that the reduction of the switching resistance was significantly important to the implementation of SSHI.

Band widening of piezoelectric vibration energy harvesters by utilizing mechanical stoppers and magnets

This paper presents a design of a piezoelectric hardening-type nonlinear vibration energy harvester which has widened resonance band while maintaining the same peak performance at the resonance frequency as that of the reference linear harvester. To this end, a pair of mechanical stoppers and a pair of repulsive magnets are introduced in this study. An experimental prototype device is designed by using a stainless steel-based piezoelectric cantilever, and numerical simulations and experiments are conducted to examine the validity of the presented design strategy. It is concluded that using the magnets to shift the resonance peak toward the lower frequency and using stoppers to expanding the resonance band toward the higher frequency can broaden the resonance band effectively maintaining the peak response. The damping due to the contact of the tip mass with the stopper is one of the key parameters which should be as small as possible to enhance the band widening effect.

SPICE Modeling of Piezoelectric Energy Harvesting Device Utilizing Stress Influence

This paper presents a SPICE modeling of piezoelectric energy harvesting (PEH) device. We developed a wireless sensor system with the PEH device as an application. The PEH device is composed of a stainless cantilever, which has a piezoelectric film on the both side surface. The PEH device oscillates at resonance frequency when the tip of the cantilever is plucked. In SPICE simulator, an equation of motion of the cantilever is described to express a mass-spring-damper system by behavioral source. The stress of the piezoelectric film is computed by theoretical calculation and FEM analysis. Then, the stress, the piezoelectric coefficient d31, and the area of the film surface formulate the electrical charge. The output voltage is given by the charge varying and an inherent capacitance. The comparison between an analysis and an experiment is represented. The output power of theoretical calculation and measurement are 310 μJ and 920 μJ respectively has occurred by plucking once. We also developed a prototype system of WSN node utilizing the PEH device. The system transmits the temperature data a few times by plucking once.