Patent ID: 8772099

Claim:
A method of detecting a detection target using a sensor, the sensor comprising a transistor selected from the group of field-effect transistors or single electron transistors, the transistor comprising a substrate having a first side and a second side, the second side being opposed to the first side, the substrate being formed of an insulating material, a source electrode disposed on the first side of the substrate and a drain electrode disposed on the first side of the substrate, and a channel forming a current path between the source electrode and the drain electrode; an interaction-sensing gate disposed on the second side of the entire substrate, the interaction-sensing gate immobilizing a specific substance that is capable of selectively interacting with the detection target, the interaction-sensing gate being formed of a conductor; and a gate disposed on the side of the channel on the first side of the substrate; the method comprising the steps of: (a) providing the detection target on the interaction-sensing gate; (b) setting a gate voltage in the gate in such a state that a transconductance of the transistor reaches a highest level; (c) selectively interacting the specific substance with the detection target; (d) when the detection target interacts with the specific substance, changing an electric potential of the interaction-sensing gate which leads to a change in a characteristic value of the transistor; and (e) measuring the change in the characteristic value of the transistor to determine a presence of the detection target.