Displayed at the Ninth Grove Fuel Cell Symposium in London last week, the project uses conventional semiconductor manufacturing techniques to etch a tiny reservoir on the surface of the chip for storing fuel, which is then refilled by diffusion out of storage.

 

The project looks ahead to a day when fuel cels become more commonplace, and autonomous devices, like sensors, will need their own sources of power. Since the device was fabricated on a CMOS-compatible chip, the technology could be integrated with today's semiconductor devices. However, the relative thinness of a chip will also mean that the fuel-cell reservoir will have to be laid extremely flat.

 

Not surprisingly, such a tiny amount of fuel requires a correspondingly low-power chip. Gilbert Erdler, a graduate student at the University of Freiburg's IMTEK (Institute of Microsystem Technology), said the cell was designed to power an autonomous sensor, such as that used on an "electronic bandage". A paper describing the chip also listed four other co-authors.

 

The fuel-cell architecture was designed for less than 100 microwatts of power. Since the chip's operating voltage -- 600 millivolts -- is known, the researchers calaculated the amount of current required -- 166 microamps -- and therefore the amount the fuel required, about 132 micrometers. In total, the chip is 4 sq. mm.

 

Storing the hydrogen required a thin palladium film about 200 nanometers thick, Erdler said, above a hydrogen diffusion barrier laid across the surface of te silicon. A 60-micrometer-thick membrane electrode assembly was laid above the hydrogen, above which are a diffusion layer and flow field.

 

The project won't produce a working model anytime soon; however, Erdler sad the chip has been demonstrated with different sample specimens.