An acoustic plate mode immunosensor

The application of an acoustic plate mode (APM) device as an immunosensor is presented. The APM sensor utilizes a Z-cut X-propagating lithium niobate (LiNbO/sub 3/) piezoelectric plate in which various types of acoustic waves are excited and received by means of a photolithographically deposited aluminium interdigital transducer (IDT). A judicious choice of the sensor operating frequency results in the selective excitation of an acoustic mode that is highly sensitive to fluid loading of the LiNbO/sub 3/ surface. This mode is then utilized as the sensing element in the sensor. Experiments have been performed using polyclonal antibodies for which the sensor has shown a strong response to the associated antigen. The biokinetics of the antigen-antibody reaction have also been studied. Experimental data compare favorably with theoretical results predicted by an affinity-purified human immunoglobulin antibody-antigen model. This immunosensor also has potential application in detecting various types of viruses such as AIDS (HIV), herpes simplex, and hepatitis. >