"A team of scientists from Joseph Fourier University in France have successfully implant biofuel cells into rats, generating 6.5 microwatts by harnessing the power of glucose. From the article: 'The device uses enzymes to harvest energy from glucose and oxygen found naturally in the body. Past attempts at using such a device in animals have failed because the enzymes have required acidic conditions or were inhibited by charged particles in the fluid surrounding cells.