Improved nanotube devices and systems/methods for fabrication thereof are provided. The present disclosure provides systems/methods for depositing controlled numbers of nanotubes with specific properties at predefined locations for the fabrication of nanotube devices. The nanotube devices may be utilized in a range of applications. A bio-fuel cell system that does not require a proton exchange membrane separator and does not need a mediator to transfer charge is provided. This exemplary bio-fuel cell uses enzyme functionalized SWNTs for the anode/cathode. The absence of a membrane in the bio-fuel cell configuration opens up the possibility of other configurations that would otherwise be unfeasible. This includes a bio-fuel cell where the anode/cathode are on the same substrate. Since the electrodes can share the same substrate, the configuration may be integrated with a circuit device on the same substrate. An IC and its power source may be fabricated on the same silicon wafer.