MUNICH, Germany — A research group of the Freiburg university (Germany) and semiconductor vendor Micronas AG has integrated a fuel cell array on a chip. The device could power autonomous microsystems, also known as 'Smart dust'.

The chip contains 42 microscale fuel cells on a CMOS device plus four cells to power the control circuitry necessary to keep the output voltage of 3.3 V constant. While the semiconductor structures have been manufactured using a standard CMOS process, the fuel cell elements — a palladium layer for H₂ storage, cathode and membrane — have been added in a post-process spin-on, explained Karl Hoffmann who oversees the project for Micronas.

According to Hoffmann, a challenge was to intelligently interconnect the fuel cells in a way that allows the control circuitry to keep the output as stable as possible during the element's life time. "With several elements in parallel and in series, it is much easier to keep voltage and current constant," Hoffmann said.

With a lifetime of about one year at nominal load in the triple-digit microwatt range, the device could eventually power smart autonomous systems in applications where no conventional power source is available. Energy harvesting devices are not regarded as competing with the chip-level fuel cell, Hoffmann said. "They rather can complement each other," he said. "A fuel cell could be used as a power buffer for periods when energy harvesting methods don't generate enough power."

Sounds like space applications? Rather not, Hoffmann said. The researchers have more down-to-earth applications in mind. Building monitoring, for instance.

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