Biological fuel cells could harness electrical energy in the body, to power low-energy devices.
Experiments with biological fuel cells are bringing researchers tantalisingly close to harnessing useful electrical energy inside the human body. Enzymes create chemical reactions that release energy, by bringing other organisms together. We know it as metabolism, and fuel cells that recreate it – using enzymes or bacteria – are a lively area of scientific research. Could future generations of heart pacemakers run indefinitely off such cells, exploiting the action of enzymes within the body to keep the current flowing without a battery?
It’s not a new idea. Back in 2007 Sony announced a ‘bio-battery’ prototype that could power small, portable speakers drawing on glucose from grape juice. Now, a team at the University of Grenoble led by Serge Cosnier has made the possibility of medical applications more plausible by running a tiny biofuel cell for 40 days in a laboratory rat. Encouraged by this successful proof of concept, the team is scaling up to an implant in a cow, with enough wattage to transmit live information out. Ultimately, even power-hungry implants like artificial kidneys and other prosthetic units could become a practical proposition.
In this biological fuel cell, the anode is a specialised enzyme that can strip electrons from freely available glucose, and the cathode is another enzyme that combines those electrons with oxygen. It could all be made more efficient, researchers say, by finding a better performing enzyme for the cathode end of the process. And future medical uses still depend on making enzymatic electrodes more stable, warns Bob Slade at the University of Surrey: there’s no point using them in complex operations when they break down in days or weeks. Slade leads a consortium of researchers at eight UK universities, funded by the Engineering and Physical Sciences Research Council under the Supergen project. The consortium also works on the other main branch of biofuel cell research: harnessing microbes to drive the electron transfer process by their action on organic material (outside the body). These microbial biofuel cells may also ultimately be developed successfully as an alternative to batteries, Slade explains, but they aren’t going to be a way of delivering power to the grid: the potential is more for self-powering low-energy devices. There are, for instance, attractive prospects for MFCs to drive environmental sensors and waste and water treatment processes, taking their energy from organic matter in the sewage itself. – Roger East
Photo: Oxford Molecular Biophysics Laboratory / Science Photo Library