Yutaka Tomimatsu

A wake-up switch using a piezoelectric differential pressure sensor

This paper reports a wake-up switch using a piezoelectric differential pressure sensor in order to reduce the power consumption of a wireless sensor node. Air pressure change surrounding the sensor is detected by using a Pb(Zr, Ti)O3(PZT) thin film cantilever with the dimension of 1500 μm × 1000 μm × 2 μm. The sensor has high sensitivity with low power consumption due to its thin cantilever and low capacitance. The sensitivity was 2.4 mV/Pa from -30 Pa to 30 Pa. It was demonstrated that the fabricated sensor performed as a wake-up switch when pressure varies in 10 Pa with low power consumption.

A piezoelectric cantilever-type differential pressure sensor for a low standby power trigger switch

This paper describes a piezoelectric differential pressure sensor using a cantilevered structure with dimensions of 1500 × 1000 × 2 µm3. A high degree of sensitivity is achieved without the power supply because only the base part of the cantilever is fixed and the piezoelectric material is used as a sensing element. The measurements indicate that the fabricated cantilever bends and a piezoelectric voltage was generated matching the piezoelectric theory for when a differential pressure is applied. The sensitivity to the applied differential pressure was 2.4 mV Pa−1 for a range between −30 Pa and 30 Pa. Additionally, it was also demonstrated that the sensor performs as a wake-up switch during the pressure shifts of 10 Pa with low-power consumption.

An AlN cantilever for a wake-up switch triggered by air pressure change

This research reports an AlN cantilever with an air chamber for a wake-up switch triggered by air pressure change. The proposed sensor is designed to fulfil both high sensitivity and low power consumption. By combining an air chamber to the one side of the AlN cantilever surface, the barometric pressure change generates a piezoelectric voltage. Thus, a wake-up switch triggered by air pressure change can be achieved using an AlN cantilever. The size of the fabricated AlN cantilever was 2000 μm × 1000 μm × 2 μm. The sensitivity to static differential pressure was 11.5 mV/Pa at the range of −20 Pa to 20 Pa. We evaluated the response of the sensor, which was composed of the AlN cantilever and the chamber of 60 ml in volume, when air pressure change was applied. The output voltage increased with increasing the applied air pressure change. It was observed that the maximum output voltage of 50 mV was generated when the air pressure change was 13 Pa.

A smart, intermittent driven particle sensor with an airflow change trigger using a lead zirconate titanate (PZT) cantilever

This paper reports on a smart, intermittent driven particle sensor with an airflow trigger. A lead zirconate titanate cantilever functions as the trigger, which detects an airflow change without requiring a power supply to drive the sensing element. Because an airflow change indicates that the particle concentration has changed, the trigger switches the optical particle counter from sleep mode to active mode only when the particle concentration surrounding the sensor changes. The sensor power consumption in sleep mode is 100 times less than that in the active mode. Thus, this intermittent driven method significantly reduces the total power consumption of the particle sensor. In this paper, we fabricate a prototype of the particle sensor and demonstrate that the optical particle counter can be switched on by the fabricated trigger and thus that the particle concentration can be measured.

A piezoelectric cantilever with a Helmholtz resonator as a sound pressure sensor

In this paper, a piezoelectric cantilever with a Helmholtz resonator (HR) is proposed as a sound pressure sensor that generates a sufficiently large output voltage at a specific frequency without a power supply to drive the sensing element. A Pb (Zr, Ti) O3 (PZT) cantilever with dimensions of 1500 µm × 1000 µm × 2 µm is designed so that its mechanical resonance frequency agrees with the target frequency. When sound pressure is applied at the target frequency, a large piezoelectric voltage can be obtained due to a high amplification ratio. Additionally, the PZT cantilever is combined with a HR whose resonant frequency is designed to be equal to that of the cantilever. This multiplication of two resonant vibration systems can generate detectable signals by sound pressures of several Pascals. The fabricated sensor generated a piezoelectric voltage of 13.4 mV Pa−1 at the resonant frequency of 2.6 kHz. Furthermore, the fabricated sensor performed as an electrical trigger switch when a sound pressure of 2 Pa was applied at the resonant frequency.

AlN cantilever for differential pressure sensor

The differential pressure sensors are used for various applications. In this work, a piezoelectric differential pressure sensor using an aluminum nitride (AlN) thin film cantilever is proposed to achieve high sensitivity and low power consumption. The dimensions of the cantilever are 1500 μm × 1000 μm × 2 μm. The proposed sensor needs no power consumption in the AlN sensing element in principle. The sensor design was validated by measuring the performance of the sensor, which showed sensitivity of 8.2 mV/Pa from -20 Pa to 20 Pa.