NOVELTY - A biofuel cell system includes an anode electrically coupled to a cathode, an electrolyte connected with the anode and cathode, a first nanomaterial on first substrate, and a second nanomaterial on second substrate. First enzyme(s) is immobilized with respect to the first nanomaterial as the anode. Second enzyme(s) is immobilized with respect to the second nanomaterial as the cathode.    USE - Biofuel cell system for use as implantable device (claimed), e.g. pacemaker, insulin pump, glucose and pressure sensor, or bionic device for stimulating the brain and spinal cord.    ADVANTAGE - The biological fuel cell is engineered on molecular scale. This biofuel cell is small and light weight because it converts fuel and oxidant to benign byproducts with the generation of electricity and it uses concentrated sources of chemical energy from the blood stream, as opposed to battery powered devices. The biofuel cell provides a continuously renewable, tailored power source because it is fueled by chemicals within the body, and can operate for long duration without the need for maintenance. The biofuel cell is non-compartmentalized and allows construction of in-vitro electrical energy generation device utilizing glucose as fuel and oxygen from the blood stream as oxidizer.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) production of nanomaterial substrate system for use as biosensor, enzymatic sensing electrode in biofuel cell, or glucose biosensor in biofuel cell, by providing nanomaterial on a substrate, depositing catalyst/promoter precursor on the substrate, and immobilizing enzyme(s) (preferably beta -nicotinamide adenine dinucleotide synthetase or glucose oxidase) to the nanomaterial; and    (2) an electrode for use as enzymatic sensor in biofuel cell, nanoelectrode in electrochemical cell, or biosensor, comprising nanomaterial vertically oriented on a substrate, and enzyme(s) immobilized with respect to the nanomaterial.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic view of non-compartmentalized biofuel cell.