Method of use of a field-effect transistor, single-electron transistor and sensor

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.