An acoustic plate mode immunosensor

A novel acoustic-plate-mode (APM) sensor for sensing antigen-antibody reactions has been developed. The APM sensor utilizes a Z-cut X-propagating lithium niobate (LiNbO₃) piezoelectric plate in which various types of acoustic waves are excited and received by means of a photolithographically deposited aluminum 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 LiNbO₃ 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 has also been studied. Experimental data compare favorably with theoretical results predicted by an affinity purified human immunoglobulin antibody-antigen model. This model immunosensor also has potentio application in directing various types of viruses such as AIDS (HIV), herpes simplex, and hepatitis