Design considerations for the acoustic waveguide biosensor

Love waveguide devices utilize shear-horizontal waves which propagate on the top layer of a coated SSBW acoustic device. Initially, attention was focused on the selection of a material which would effectively guide the Love wave. Silica and polymethyl methacrylate were used as guiding layers and the mass sensitivity of the corresponding sensors was tested in air. Low-shear-acoustic-velocity polymer overlayers were found to guide the Love wave most effectively with a maximum sensitivity of . The polymer waveguide sensor was further used to detect protein adsorption on the polymer surface from IgG solutions within the concentration range of 1 - . Radiolabelled IgG was applied to the device surface in order to calibrate the wave response to protein surface mass density. Finally, the effect of the acoustoelectric interaction on liquid-based applications was studied by utilizing a three-layer waveguide geometry. It was found that the evaporation of a 50 nm gold layer on the polymer overlayer can be used to eliminate acoustoelectric interactions without interfering with the Love wave propagation. After activation with protein A and IgG, the above system was used successfully to detect the direct binding of 400 ppb atrazine.