Analysis of viscous losses is the chemical interface layer of Love wave sensors

Love waves have been introduced as highly effective devices for liquid-sens ing applications, For chemical sensors, a microacoustic delay line featurin g a multilayered waveguide supporting a generalized Love wave mode can be u sed in an oscillator setup. The top layer of the waveguide is a chemical in terface, which selectively adsorbs certain target molecules in the adjacent liquid. The increase in mass density caused by adsorption can be detected as changes in the oscillation frequency. Commonly used interface materials show viscoelastic losses leading to an unwanted damping of the wave. To kee p the signal-to-noise ratio high, the total insertion loss of the delay lin e should be kept as low as possible. Furthermore, it must not exceed a cert ain value to allow the electronic circuitry to sustain the oscillation. Tr We analyzed the viscoelastic losses, which strongly depend on the frequency being used. By means of the proposed theoretical approach, the maximum thi ckness of the interface layer can be determined not to exceed the losses th at can be handled by the driving electronics.