Tooru Nomura

Measurement of acoustic properties of liquid using liquid flow SH-SAW sensor system

The SH-SAW resonator having narrow bandwidth and higher Q value has been used for sensing the properties in ionic and viscosity of liquid. The surface acoustic waves with the shear horizontal displacement (SH-SAW) are excited on a piezoelectric substrate; 36 rotated Y cut X prop. LiTaO3 (36 YX LiTaO3) and the liquid flow sensing system was constructed by using two-port resonator on the substrate. The flow of a sample liquid was interacted with the SAW only on the cavity of the resonator. The resonator was connected in an amplifier, to construct an SH-SAW oscillator. The frequency changes of the SH-SAW oscillator were detected as a sensor response. Experimental results showed that the response of the SAW sensor varied with both the conductivity and the square root of product of the density and viscosity of the liquid. Transit responses of the SAW sensor system to the flow of the sample liquid also showed a specific feature. It was found that these quantities were very useful to determine the properties of liquid.

Chemical sensor based on surface acoustic wave resonator using Langmuir-Blodgett film

A one-port surface acoustic wave (SAW) resonators incorporating Langmuir-Blodgett (LB) films has been investigated. SAW sensors are one potential applications of SAW devices. Most of the work reported on SAW sensor concerns delay lines. In this paper we characterize the mass loading effects of one-port resonators by depositing successive monolayers of LB films onto the surface. A 90 MHz SAW gas-phase sensor has been fabricated on an ST cut quartz substrate, and one-port resonator configurations have been used as the sensing element. Ultra thin monolayers of arachidic acid and arachidic acid ethyl ester have been deposited using the LB method. The resonant frequencies and the Q values have been measured as sensor response. Experimental results show that the Q values and the resonant frequencies of the one-port SAW resonator vary with film mass loading on the SAW device surface.

Measurement and Mapping of Elastic Anisotropy of Solids Using a Leaky SAW Excited by an Interdigital Transducer

Abstmt-Methods of measuring the acoustic properties of solids using acoustic beams in a liquid generated by interdigital transducers (IDT) are described. An IDT can radiate acoustic waves into a liquid in oblique directions with respect to the substrate, and the wave fronts can be arbitrarily controlled by designing the IDT shape. When the acoustic beam is incident on the solid sample-water interface near the Rayleigh angle, the reflection field is equal to the superposed fields of the specular reflection and the reradiation from the leaky surface acoustic wave (SAW) excited on the sample. One normal IDT pair on a piezoelectric substrate is used to measure the acoustic properties of a solid sample. The velocity and the attenuation of the leaky SAW on the sample can be obtained by measuring the trailing field due to the reradiation. A new method for focusing the beam from an IDT and mapping a leaky SAW velocity on a solid sample surface is shown. An interdigital electrode is divided into several sections, each of which is positioned to form a one-dimensional Fresnelphase-plate interdigital transducer (FPP IDT) on a piezoelectric substrate. It has been found that the FPP IDT generates a converging beam onto a focal plane, and the present system is suitable for measuring the two-dimensional variation of the leaky SAW phase velocity on a sample surface. T

Measurement of acoustic properties of liquids using SH-type surface acoustic waves

A surface acoustic wave (SAW) viscosity sensor for liquid phase sensing utilizing a shear horizontal displacement of a leaky SAW is presented. The sensor is based on a dual SAW delay line oscillator. Leaky SAWs with shear horizontal displacement were excited on a 41 degrees -rotated Y-cut X-propagation LiNbO/sub 3/ substrate by using interdigital transducers (IDTs). It is shown that the viscosity sensor has a sensitivity of about 80 Hz/cP at an operating frequency of 30 MHz, with a threshold sensitivity of about 1 cP.<<ETX>>

Surface acoustic wave liquid sensors based on one-port resonator

A one-port resonator utilizing shear horizontal surface acoustic waves (SH-SAWs) has been used for sensing applications in liquids. SH-SAWs have been excited on a 36°-rotated Y-cut X-propagating LiTaO3 substrate using interdigital transducers and the one-port resonator configuration has been used as a sensing element in liquids. The sensitivity of the resonance frequency and the Q value for the viscosity of liquids have been measured. Experimental results showed that the resonance frequency and the Q value of the SH-SAW resonator varied with the viscosity of the loaded sample liquid.

Humidity Sensor Using Surface Acoustic Wave Delay Line with Hygroscopic Dielectric Film

A surface acoustic wave (SAW) sensor for measurement of humidity in ambient atmosphere is presented. SAW technology is increasingly being used in sensors. The majority of the work reported on SAW sensors to date has studied the effect of mass loading. In this paper, we propose a new SAW humidity sensor that uses the changes in the film permittivity rather than the mass. A 30 MHz dual SAW delay line fabricated on 128° YX LiNbO3 was coated with cellulose acetate. This hygroscopic polymer coating caused a SAW velocity change of 0.36 m/s per 10% relative humidity. The response was linear in the range from 10% to 80% in relative humidity.

Liquid sensor probe using reflecting SH-SAW delay line

Abstract A new liquid sensor probe has been designed by using SH-SAW device. Shear horizontal mode surface acoustic wave (SH-SAW) has a unique characteristic of complete reflection at the free edges of the substrate. The SH-SAW are excited on a 36° YX LiTaO3 and the right angle edge of the substrate has been used to reflect the SAW. Multi-channel reflecting SAW delay lines were constructed on the substrate. Both the phase and amplitude of the SH-SAW reflected from the edge were measured as a sensor response. Several experiments were performed to verify the edge reflection type SAW sensor in liquid phase. A sensing system configuration is also suggested for the effective operation of the sensor probe. An electronic circuits system for accurately measuring the phase characteristics of the reflected wave and for detecting the output from the multi-channel SAW sensor probe was shown.

Measurement of Velocity and Viscosity of Liquid Using Surface Acoustic Wave Delay Line

There is increasing use of surface acoustic wave (SAW) in sensors, and the majority of the work reported on sensors to date has used Rayleigh waves on piezoelectric materials. In this paper, a leaky SAW delay line was used for measuring the acoustic properties of liquids. The leaky SAW with the shear horizontal displacement is excited on a piezoelectric substrate using interdigital transducers. The velocity and viscosity of liquids are measured using the leaky SAW delay line. Experiments are made with a rotated Y cut LiNbO3 substrate. Results shown that the method is very suitable for sensing liquid.

Precise Measurement of Surface Acoustic Wave Velocity Using a Swept Frequency IDT-NDE System

A method of measuring the surface acoustic wave (SAW) velocity is presented. Three interdigital transducers (IDTs) deposited on a piezoelectric substrate are used to measure SAW velocity of sample materials using a fluid couplant. The output voltage of the IDT is measured as a function of the acoustic wave frequency. A unique curve is obtained by the interference between the two outputs of the close IDTs. The SAW velocity is obtained from the frequency dependence of the curve. Measurements are made for anisotropic materials at frequencies from 20 to 30 MHz. The experimental results obtained in this manner agreed with the theoretical ones.

Measurement of Humidity Using Surface Acoustic Wave Device

A surface acoustic wave (SAW) sensor utilizing the acoustoelectric effect has been designed for measurement of humidity in sensing ambient atmosphere. Most of the studies reported on sensors utilize the effect of mass loading. In this paper, we propose a somewhat different SAW humidity sensor that uses the changes in the film conductivity rather than the mass. A 30 MHz dual SAW delay line fabricated on 128° YX LiNbO3 was coated with the sodium salt of poly(styrene) sulfonate. This hygroscopic polymer coating caused the SAW velocity change of 10 m/s per 10% relative humidity. The response was quite linear in the range from 20 to 70%RH.