MHz SAW Resonators Research Articles

Detection of cellular damage by hydrogen peroxide using SV40-T2 cells on shear horizontal surface acoustic wave (SH-SAW) sensor

The rat lung epithelial cell line SV40-T2 was used to develop a cellular biosensing system to assay for environmental toxicants. The novel approach on which this system is based involves direct attachment of cultured rat or human cells onto a cell-adhesive matrix on the device through which shear horizontal surface acoustic waves (SH-SAW) are transmitted using 50MHz SAW resonator. This novel design enables sensitive monitoring of changes of the electrophysical characteristics of cells, such as their conductivity and relative permittivity. A time-dependent change of phase of SAW and change of insertion loss (change of amplitude) were observed when the cells were treated with 0.5 or 1.0mM H2O2. The change of insertion loss was biphasic, with an early phase (1–3h) and a late phase (3–6h). The late phase coincided with the destruction of cell–cell tight junctions detected by measurement of the transepithelial electrical resistance and paracellular permeability; in contrast, the early phase coincided with the destruction of intracellular actin filaments by H2O2. The early-phase effect of H2O2 on phase shift may be attributable to the change of intracellular permittivity by a change of cellular polarity. Immunofluorescence microscopy showed the disappearance of zonula occludens protein 1 from the region of cell–cell contact. These results suggest the correlation between the change of insertion loss as an SAW parameter and the destruction of tight junctions of the cells on the SH-SAW device in the late phase.

Effect of Substrate Thickness on Quasi-Longitudinal Leaky Surface Acoustic Wave Propagation on Quartz

Propagation properties of a quasi-longitudinal leaky surface acoustic wave (QLL-SAW) on rotated-Y cut quartz are described. It is found that by reducing the relative thickness of the quartz substrate, i.e., the ratio of the substrate thickness to the SAW wavelength, the Q-value of a QLL-SAW resonator can be improved. Its phase velocity is about 5704 m/s, which is close to the velocity of a longitudinal BAW (5750 m/s) and about 1.8 times that of a Rayleigh SAW. Propagation characteristics are simulated by a finite element method. The results obtained indicate that many guided wave modes exist near the velocity of the longitudinal BAW and strongly couple to QLL-SAW modes. Experimental results show that these guided wave modes affect QLL-SAW propagation and deteriorate resonator Q-values. By reducing the relative thickness of the quartz substrate, the frequency difference between the QLL-SAW and the guided wave modes is increased, which weakens the coupling. As a result, 700 MHz SAW resonators having a Q-value of more than 8000 are realized.

In situ UV-photopolymerization of gas-phase monomers for microanalytical system applications

The controlled growth of thin polymer films by in situ UV-photopolymerization of vapor-phase monomers in the absence of a photoinitator is described and the use of this process for integrated sensor-array interfaces, etched-channel separation column stationary phases, and passivation layers within microanalytical systems designed for the determination of gases and vapors is considered. Following preliminary tests with methylmethacrylate, attempts were made to grow polymer films from four commercial silylated methacrylate monomers on substrates of silicon, glass, and/or ST-quartz. Continuous films of poly[(trimethylsilyl)methylmethacrylate] (PMTMS) and poly[(phenyldimethylsilyl)methylmethacrylate] (PMPDMS) were grown to thicknesses of ∼30–300 nm, while attempts to grow films of poly[((tris-trimethylsiloxy)silyl)propylmethacrylate] and poly[propylsilatranylmethacrylate] were unsuccessful. Chlorotrifluoroethylene was used to grow films of potential use as passivation layers. Films of PMTMS were patterned using a quartz photomask with 300 μm lines and spaces, and were grown on vertically aligned substrate surfaces, as models of high-aspect-ratio etched-channel walls. PMTMS and PMPDMS films were then grown directly on working 250 MHz SAW resonators subsequently exposed to a series of organic vapors. Response profiles, calibration curves, and relative response patterns were examined. Results, though mixed, demonstrate the feasibility of this approach for producing polymer thin films for microanalytical system development.

Multi-Channel SAW Chemical Sensor Using 90 MHz SAW Resonator and Molecular Films Deposited by Droplet-Surface Casting Method

Abstract The objective of the present study is to build a chemical sensor utilizing the feature of a high frequency SAW device for enhansing the sensor sensitivity and the feasibility of making a multi-channel structure on the substrate for integration of plural sensors. We developed the fine casting method (which was named as “droplet - surface casting method”), and deposited several kinds of adsorption films on the channels of a SAW device. The device was ST cut Quartz 9OMHz SAW resonator chips, each of which has 2 resonators on a substrate. We constructed 4-channel odor sensing system that have one reference channel and three sensing channels using the two chips, and measured the response patterns of the organic solvents which have same carbon number and different atomic groups.

Ionizing space radiation effects on surface acoustic wave resonators

Two available types of single pole 199 MHz SAW resonators were irradiated to determine space radiation performance, some fabricated on air-swept 40 degrees Y-rotated quartz substrate, and some fabricated on non-swept quartz. In addition, some of the resonators on non-swept quartz were coated with 400 AA RF sputtered layer of SiO/sub x/. It was found that sensitivity to radiation is substrate material dependent, with pure substrates showing less radiation degradation in performance. An unexpected reduction in sensitivity was found for the coated devices. >

SAW Device Application to Public Telecommunication System in Japan

SAW devices for a public telecommunication system which have been put into practical service are reviewed and the near future SAW device application is presented. A 400 MHz SAW timing tank for an F-400M optical fiber transmission system and a 145 MHz SAW resonator stabilized voltage-controlled-oscillator for land mobile telephone system are the only two devices now in practical use. But the use of SAW devices is increasing steadily because of their high frequency fundamental mode operation, good reproducibility, and excellent aging characteristic.