An on-chip fuel cell that can be powered by a variety of fuels has been developed by Japanese scientists. The fuel can be chosen to suit the cell's application, from laptops to mobile phones, they say.

A variety of fuels can power the microchannel-based on-chip fuel cell

Many research groups are working on miniaturising conventional fuel cells but, as yet, they are not compatible with other micro-devices. Tetsuya Osaka and colleagues from Waseda University, Tokyo, have made a microchannel-based fuel cell that is pump-free, membraneless and air-breathing (it uses oxygen from the air as its oxidant). Its simple monolithic design - its two electrodes are made in a single substrate - means it is easier to make than conventional fuel cells, says Osaka.

Osaka had previously tested the fuel cell using methanol. Methanol is suitable for long-life applications but is toxic, he explains, so he repeated the test using ethanol and 2-propanol. Ethanol is less toxic and renewable, he says, while 2-propanol is suitable for high power devices because it doesn't generate catalyst-poisoning carbon monoxide. He found that ethanol and 2-propanol generated voltages comparable to that of methanol. He also improved the fuel cell's safety by replacing the acidic electrolyte with a phosphate buffer, which kept the pH neutral without significantly affecting the power output.

Changming Li, a fuel cell expert at Nanyang Technological University, Singapore, describes the work as 'a new approach to develop efficient micro power sources by using micro-electro-mechanical systems' and adds that it demonstrates advances in both microfabrication and energy systems.

Osaka says he is working towards integrating the fuel cell with other micro-devices to demonstrate they work in a real system. 'This work will help contribute to the development of micro-devices because they will have their own power source on the same chip,' he predicts. He adds that a possible goal would be an on-chip blood-screening sensor powered by glucose in the blood.

Emma Shiells

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