N-type polymer based electrochemical devices include one or more source electrodes, one or more drain electrodes, one or more channels, a gate electrode, and an electrolyte solution are disclosed. The channels include one or more n-type polymers and one or more enzymes. The gate electrode includes one or more n-type polymers and one or more enzymes. The source and the drain electrodes are electrically connected by the corresponding channel. The electrolyte solution contains one or more metabolites capable of reacting with the one or more enzymes in the channel and the gate electrode and is in electrical contact with the channel and the gate electrode. Saturation current that flows through the channel increases when the metabolites react with the enzymes to produce electrons, which are directly transferred to the n-type polymers at the gate electrode and the channel. Methods of making and using the n-type electrochemical device are also disclosed.