Target proteins diffuse down through the sample and are captured by antibodies anchored to a SAM on the gold sensing pad. Their charge shifts the pad's surface potential, which the remote MOSFET reads as a threshold-voltage shift.
Target proteinNon-target (no binding)AntibodyAu extended gate
Bound 0 / 7ΔVth0 mV
Binding → surface charge → effective gate voltage → drain current. Only the target fits the antibody binding sites; non-target molecules wander and wash away, so the signal stays specific. Values are illustrative.