Abstract
A biosensor includes a substrate, an electrode layer, a conductive polymer layer and a bio-recognizing element. The electrode layer is disposed on the substrate. The conductive polymer layer is disposed on the electrode layer and partially covers the substrate. The bio-recognizing element is disposed on the conductive polymer layer. A chemical reaction takes place between the object and the bio-recognizing element, and the chemical reaction decreases the conductivity of the conductive polymer layer.