The Next Sustainable Power Source: Your Body?

Fuel cells are being built that are small enough to be implanted in the body, says Eric Doyle. Could they replace mobile phone chargers?

Bio fuels are being seen as a green solution to the increasing power demands of the aerospace and automotive industries. At the other end of the power scale, researchers are searching for lower-yield fuel cells that will render similar benefits – from our own bodies.

A recent BBC news story highlighted researchers, led by Dr Serge Cosnier at the Joseph Fourier University of Grenoble, who are investigating the possibility of developing biofuel cells that geneate electricity, using glucose and oxygen at concentrations found in the bod.

The first aim of the research is to power implanted organs and artificial limbs without the need for batteries, but the concept could also charge smartphones or other devices from these sustainable power sources. Such a move is unlikely to stem from the Grenoble work because the process requires a fuel cell to be implanted in the body. But nothing is impossible.

The concept of bodily fluids being used as an electrolyte has been around since the 1970s but the power produced was considered too small to be of any real use and it was laid aside. In 2002, Professor Itamar Willner revived the concepts and published an article in Science magazine in which he predicted: “In 10 years time you may see bio fuel cells in laptops and mobile phones.”

We’re still waiting to see any commercial systems but Wilner’s prediction may only be a few years out. Two years ago Sony announced a biofuel cell that uses glucose and water to power an MP3 player. The fuel cell uses sugar and water to make electricity and this would be an attractive proposition where no conventional electricity supply is available.

Photosynthesis behind the process?

But what about the supply of glucose? Researchers in several countries, including in theUK at Southampton University, are looking at photosynthesis, which produces glucose in plants, as an alternative power generator.

One of these teams, working at Berkeley University of California, is using bacteria injected into tobacco plants to produce a reasonable yield of electricity. The bacteria cause the plant to produce chromophores, growths that photosynthesise, which can be used to produce a small but useful voltage.

The idea of using vegetation as mini solar cells does have its appeal. The system is biodegradable, renewable and also improves the environment – and makes it look prettier. But it does not do much for mobility.

The IT ideal would involve the body being used to generate the power – but using body fluids rather than piezoelectric crystals, or thermocouples to harness body heat.

The Grenoble researchers are investigating how their cells could be improved: they propose that their fuel cell could take the place of batteries which need to be replaced every five years at present. This means that a 70 year old with a pacemaker implant has to undergo further surgery when the battery needs replacing. This is undesirable because of the trauma it causes for an ageing patient.

To have a good replacement, the fuel cell must have a lifetime substantially longer than that – but at the moment the lifetime of the Grenoble implants is not known. It looks like they could last for many years but there is no guarantee.

The challenge is how a fuel cell can be implanted on, or just under, the skin and still access suitable fluids for generating power. If this problem can be cracked, it may result in on-the-go charging of mobile devices that would be palatable to the average user while doing its small bit for the environment.