Figure 1.

Conceptual design of an FET biosensor. The Au gate electrode was connected to the extended gate of a silicon-based n-channel FET, and gate voltage (V_G) was applied through the Ag/AgCl reference electrode. Probe molecules such as MIP, which selectively bind to analytes but not impurities, are tethered on the gate electrode of the FET device. Molecular charges of analytes at the solution/gate electrode interface induce a change in V_G at a constant source–drain current (I_D) and drain voltage (V_D).