A Lithium-Tantalate Based Acoustic Reflective Delay Line for Chemical Sensing in Water

Surface acoustic delay lines patterned on lithium tantalate piezoelectric substrate propagating a guided shear wave is demonstrated for direct detection chemical sensing in aqueous solutions with no need for additional microfluidic handling. The high dielectric permittivity substrate prevents excessive losses from capacitive coupling with water when dipping the whole chip, including interdigitated electrodes, in water, while the shear wave only couples with the first few hundred nanometers of the adsorbed layer. A measurement of non-specific protein detection demonstrates the principle.