The viscoelastic contribution to polymer-coated SAW sensor for TNT vapor detection

A perturbational approach is used to examine the velocity and attenuation responses of polymer-coated SAW sensor before and after vapor adsorption. To reach the goal of detecting the 500 ppb level, we find the h0 satisfying h0 ≈ hres/10 is enough. The slope of linear part of the velocity shift for the glassy-rubbery and rubbery is greater than that of glassy film. The slope between the glassy-rubbery and rubbery is almost the same in linear part. But plasticization causes the rubbery film to easilier behave as an acoustically thick one than glassy-rubbery and glassy polymer. To keep stable oscillation in vapor sensing, the induced attenuation should be reduced as much as possible and the linear velocity changes are preferable. Therefore, the glassy-rubbery film is suitable for a chemical interface because it promotes higher sensitivity than glassy film, larger linear range than rubbery film and easier to avoid resonance than rubbery film.