Methods, systems, and devices are disclosed for implementing a biofuel cell device for extracting energy from a biofuel. In one aspect, a biofuel cell device includes a substrate, an anode including a catalyst to facilitate the conversion of a fuel in a biological fluid in an oxidative process that releases electrons captured at the anode, thereby extracting energy from the fuel substance, a cathode configured on the substrate adjacent to the anode and separated from the anode by a spacing region, and a load electrically coupled to the anode and cathode via electrical interconnects to obtain the extracted energy as electrical energy.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with government support under grants CBET-1066531 and CHE-1057562 awarded by the U.S. National Science Foundation (NSF) and the U.S. Department of Energy (DOE). The government has certain rights in the invention.