Study of the Effect of the Operating Frequency of a GaN Lamb Wave Device to Viscosity and Protein Sensing

Shear-operating frequency is known to affect the sensitivity of acoustic wave sensor devices to both chemical and biological sensing, e.g., the detection of solutions' viscosity and protein adsorption. Lamb wave devices have been considered to be limited to low operating frequencies (5-40 MHz) due to their configuration. Here, acoustic devices based on single crystalline GaN membrane were used for liquid-based applications by monitoring the lowest symmetrical mode S0 of a Lamb wave in the range of 142-458 MHz. We evaluated the response of the acoustic devices by monitoring the amplitude and phase of the wave during the application of various concentrations of glycerol on the device surface. In addition, we demonstrated a strong correlation between mass sensitivity and device operating frequency, as measured during the specific binding of biotinylated IgG on the neutravidin modified membrane. Importantly, our results indicate that a decisive parameter in choosing the optimum frequency is the nature of the final application. Lower operating frequencies (<;200 MHz) appear to be more suitable for viscosity measurements, while higher ones (~300 MHz) should be selected for biosensing applications.