Patent ID: 8038943

Claim:
A method of detecting a presence of target bio-molecules or a concentration of the target bio-molecules using a field effect transistor, the method comprising: allowing a first sample including a first target bio-molecule to contact a sensing surface of the field effect transistor; flowing the first sample including the first target bio-molecule across the sensing surface of the field effect transistor without binding the first target bio-molecule to a fixed position; measuring a change in an electric signal of the field effect transistor, the field effect transistor comprising: a substrate, a source region; and a drain region, wherein the source region and the drain region are formed apart from each other on the substrate, and the source region and the drain region are each doped having an opposite polarity than a polarity of the substrate, and wherein a channel region is disposed between the source region and the drain region and an insulating layer is disposed on the channel region and includes the sensing surface, and determining a presence of the first target bio-molecule using the measured change in the electric signal of the field effect transistor, wherein changes in the electrical signal resulting from a change in pH due to the flowing of the first sample are disregarded in the determining of the presence of the first target bio-molecule.