SH-SAW biosensor on quartz
This paper describes a shear horizontal surface acoustic wave (SH-SAW) immunoassay biosensor on a quartz substrate. The SH-SAW biosensor is a 250MHz SH-SAW delay-line which has a gold surface covered with antibodies. It is important to discuss the detection mechanism of SH-SAW biosensors on quartz. In this paper, the detection mechanism of SH-SAW biosensors are investigated, using three methods of numerical analysis. The first method is a mass loading model analysis. The second method is a viscosity model analysis. The third method is a viscoelasticity model analyasis. A numerical calculation method for SH-SAW propagation characteristics, which is a modified Campbell and Jones method involving the effect of liquid viscosity is applied to quartz. In order to confirm the proposed numerical analysis models, 250MHz SH-SAW biosensors on quartz substrates were tested. The mass, viscosity, and viscoelastic behavior of fluids on SH-SAW biosensors were theoretically and experimentally discussed.
Viscoelastic behavior of antibody films on a shear horizontal acoustic surface wave sensor.
To study the viscoelastic behavior of antibody films on a surface acoustic wave device, we have measured the influence of multiple layers of antibodies onto the propagation of the wave. Attenuation and sound velocity variation caused by up to 20 layers have been measured. The results can be interpreted with the propagation of a viscously damped Love wave in a film with an extremely low velocity of sound. From our results, we conclude that, for the one- or two-layer films normally used in acoustic wave immunosensing, a pure mass effect is dominant. For thick films, a saturation of the sensor response is observed.
Power Flow Angles for Slanted Finger Surface Acoustic Wave Filters on Langasite Substrate
Power flow angles (PFAs) on a langasite (LGS) substrate with Euler angles of (0°, 138.5°, ψ), ψ=25.7 to 27.7° are investigated for slanted finger interdigital transducer (SFIT) surface acoustic wave (SAW) filters by an electrical and optical methods. In the electrical method, several tilted SFIT SAW filters with different tilt angles for (0°, 138.5°, ψ) LGS substrates were designed, and the frequency responses of the filters were measured. In the optical method, the PFAs were directly measured by optical probing for a parallel interdigital transducer (IDT) with wide propagation area on the substrate. As a result, a good correlation between electrical and optical measurements of the PFAs is obtained, but the calculated PFAs are slightly different from the measured PFAs. A good frequency response of a tilted 380 MHz SFIT SAW filter with an appropriate tilt angle corresponding to the PFA on the substrate is obtained even though the aperture is small.