Nano 'Yarn' to Power Biomedical Implants

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Imagine a pacemaker or bionic ear that doesn't require batteries but is powered by your very own cells.

That could be the future of biomedical implants once biofuel cells come to fruition, says an international team of scientists, who have taken the technology one step closer to reality.

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The researchers have created a biofuel cell made from carbon nanotubes that generate energy from blood glucose.

The advance improves the power output and the lifetime of biofuel cells, they report in the journal Nature Communications.

Unlike batteries, which store chemical energy, conventional fuel cells convert a fuel such as hydrogen or methanol into electricity.

Biofuel cells, which have been in development since the 1960s, employ the same principle except they use biological enzymes to convert glucose into electricity inside the body.

However, there have been a number of serious technical hurdles that have impaired their performance, says study co-author Professor Gordon Wallace from the University of Wollongong.

One of the challenges is "immobilizing" the enzyme that converts the fuel into electricity and making it stick to the electrodes of the fuel cell, rather than diffusing through the cell and into the fuel.

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Another challenge is keeping the immobilized enzyme active for long periods of time.

"This is because the electrodes, like anything implanted in the body, tend to get fouled and performance drops off quite quickly with time," says Wallace.

This has resulted in low power densities of only a few milliwatts per centimeter squared and a lifetime of only a few days, which is insufficient for practical use.

To tackle these problems Wallace and his colleagues turned to carbon nanotubes, which are microscopic cylinders made from long strings of interconnected carbon atoms.