Horizontal Surface Acoustic Wave Devices Research Articles

Droplet Streaming and Nebulization Induced by the Shear Horizontal Surface Acoustic Wave

Droplet streaming and nebulization on a shear horizontal surface acoustic wave device made of 36o Y-cut LiTaO3 have been reported. The streaming pattern inside the droplet is sensitive to the droplet shape, the position to the interdigital transducer, and the aperture size. Droplet nebulization was enhanced with the increased aperture size of the driven IDTs and mainly occurred in horizontal direction along two lateral sides of the droplet, which is perpendicular to the designed SAW propagation direction. The atomization duration increases with the droplet size and decreases with the driven power at a given droplet size. The maximum rate of the atomization is ~0.2 μL/s at an applied power of 6.7 W. This provides a simple and effective method of the integration of both bio-liquid sensing and fluid manipulation on a single substrate for lab-on-chip biosensing platform.

Cell-based Acoustic Sensors for Biomedical Applications

The development of a novel surface acoustic wave biosensor for liquid phase ligand detection is described in this paper. The functional layer of the biosensor comprises human embryonic kidney cells that can be efficiently used for the expression of specific ligand receptors and is coupled to the acousto-electric transducer. We outline the successful design and development of a low loss shear horizontal surface acoustic wave device for detection of receptor-ligand interactions in heterologous systems. The proof of concept implementation of a protocol to immobilize cells expressing either muscarinic acetylcholine or insect olfactory receptors on the device surface has been successful. In addition, the background effect of the cell growth medium has been examined and results presented. We believe that this biological sensor also can be used more generally to monitor cell viability when challenged with toxins, drugs or other substances.

High‐sensitive neural network ammonia sensor based on shear horizontal surface acoustic wave devices

AbstractIn this paper, a shear horizontal surface acoustic wave devices coated with L‐glutamic acid hydrochloride were applied as ammonia sensors. This sensor has shown high sensitivity and fast responses to ppb‐level ammonia. The frequency shift linearly increased as the ammonia concentration increased from 40 to 400 ppb in dry environment. In the humid environment, the frequency shift gradually decreased with ammonia concentration increasing. In order to precisely estimate the ammonia in humid environment, two different neural models, the conventional feedforward neural network and quantum neural network, were used as the identifier and their performances were reported and compared. Copyright © 2008 John Wiley & Sons, Ltd.

Development of methanol sensor using a shear horizontal surface acoustic wave device for a direct methanol fuel cell

A methanol sensor for direct methanol fuel cell (DMFC) is required. A shear horizontal surface acoustic wave (SH-SAW) sensor for electrical property determination is applied for this purpose. The operating temperature of DMFC is above 50 °C. The wave propagation characteristics were calculated while considering temperature coefficient. The results indicate that the sensitivity increases with increasing temperature. Then, the concentrations of methanol solutions were measured using the SH-SAW sensor. Measured temperature ranged from 25 °C to 60 °C and concentration ranged from 0 to 50% by weight. Linear relationships between the sensor response and concentration were obtained. An increase in the sensitivity is experimentally confirmed. The limit of the detection was estimated from experimental results to be 0.1% by weight. Because formic acid is produced in the DMFC electrode reaction, its effect was discussed. The concentrations of mixture solutions of methanol and formic acid were measured. Using a chemometric method, we succeeded in determining the concentrations of both, simultaneously. Therefore, the SH-SAW sensor can be possibly used for DMFC.

Development of Smart Tongue Devices for Measurement of Liquid Properties

In this paper, we describe the design and characterization of shear horizontal surface acoustic wave devices for the analysis of liquid samples. Devices were fabricated on both 36/spl deg/ rotated Y-cut X-propagating LiTaO/sub 3/ and LiNbO/sub 3/ substrates. The design consists of a dual delay-line configuration where one delay line is metallized and shielded, while the other is left electrically active. Experiments to characterize the devices in terms of sensitivity, temperature dependence, and mass loading have been conducted and the results presented. Different liquid samples, i.e., water, orange juice, and milk, are 100% linearly separable using principal components analysis. In addition, it is possible to measure the fat content (/spl plusmn/0.1%) as well as the freshness of full (whole) milk.

Experimental Study of Love Wave Sensor Response by Phase and Group Velocity Measurement

The effect of dispersion on acoustic wave sensors is considered experimentally. A recent theoretical prediction that the phase velocity mass sensitivity of guided shear horizontal surface acoustic wave devices can be obtained using measurements of phase and group velocity, and that the group velocity is highly sensitive to mass loading, is investigated. Experimental data for a polymer-coated surface-skimming bulk wave device on an ST quartz substrate is presented. Measurements of phase velocity, group velocity, and insertion loss determined by a network analyzer were obtained by systematically increasing the guiding layer thickness. Liquid sensing using poly (ethylene glycol) solutions with increasing densities were performed and phase and group velocities measured. The increase in mass sensitivity with the guiding layer thickness is significant and the data confirms the theoretical prediction that group velocity is a more sensitive parameter than the phase velocity to liquid loading.

Measurements of Conductivity and pH of Liquid Using Surface Acoustic Wave Devices

The use of a shear horizontal surface acoustic wave device in measurements of conductivity and pH of liquid is described. The device has two parallel SAW delay lines fabricated on 36° rot Y cut X-prop. LiTaO3. The propagation surface of the one delay line is metallized but that of the other has no metallized area for an acoustoelectrical interaction with a liquid. The conductivity and pH of a liquid are measured by the differential signals of the both delay lines. Some acid and alkali solutions are examined. The SAW sensor is applied to the study of an enzyme-substrate reaction that shows the change in pH.