A field effect transistor including conventional source and drain electrodes employs, in the gate region, a layer of antibody specific to a particular antigen. An electrolyte solution such as 0.155 Normal sodium chloride atop the antibody layer provides a predetermined drain current versus drain voltage...http://www.google.com.hk/patents/US4238757?utm_source=gb-gplus-share專利 US4238757 - Field effect transistor for detection of biological reactions
