Power plant on a chip

Scientists at Lehigh University are developing a tiny generating plant, housed on a silicon chip, that they believe can produce enough hydrogen to run power-consuming portable devices.

The amount of hydrogen produced was small, but it was enough to demonstrate that the Lehigh project is feasible. Given time the Lehigh group believes they will develop a working generating plant, housed on a silicon chip that produces sufficient quantities of hydrogen to run different types of power consuming portable devices.

‘About 10 years ago people starting thinking: ‘can we take the same fabrication methods for silicon chips and instead of using them for electronics, use them for something else?” said Mayuresh Kothare, assistant professor of chemical engineering.

Instead of a processing device for electrons, chips would become miniature chemical reactors or power plants. Kothare said that in one experiment a silicon chip was turned into a tiny steam engine.

The channels normally used to transmit electrical current were used to carry steam. They could just as easily have been used to carry various reagents to fuel miniature reactors or generating plants housed in the chip’s processing areas. In an experiment at the Sandia National Laboratory in New Mexico scientists created a miniature geared engine on a chip.

‘At Lehigh our chip-based micro-chemical plant will take a reagent, such as methanol, or a hydrocarbon, like diesel or gasoline, and carry it to a tiny reactor to produce hydrogen,’ Kothare said. ‘We have already produced hydrogen and have been able to get the reagents into the reactor to carry out the necessary reaction.’

The hydrogen will be collected in a miniature fuel cell that can power an electronic device.

The chip is the same size as an ordinary electronic chip, approximately three centimetres by three centimetres. Small cartridges of methanol, or other hydrocarbons that are fed to the ‘reformer’ by micro-capillaries or miniature fuel lines would fuel the micro-plant.

The reformer would be heated by electricity and the reaction would produce hydrogen, which would be transmitted to the fuel cell via another network of micro-capillaries.

While one chip could not produce enough power to operate a laptop, Kothare said that by wrapping scores or hundreds of the tiny micro-plants together – called ‘numbering up’- enough power could be produced to operate all kinds of electronic devices.

A recent experiment in Germany demonstrated that a hydrogen micro-fuel cell powered a laptop computer for up to ten hours whereas the operating time of an ordinary rechargeable laptop battery is generally about two hours.

Currently, one of the hurdles in creating a working plant is getting the reagents into the micro-capillaries. ‘Think of piping in your own house,’ Kothare said. ‘You can buy standard fittings but there are no standard fittings for the chip plant and there are no standardised pipes. To get the reagents in is a whole world of its own. You don’t know how much will leak or vaporise or if it is sealed tightly.’

While Kothare and his colleagues are working on a chip-based power plant, he observed that there could be unlimited uses for devices developed from microchips.

One use could be the implantation of a processing chip inside the body to conduct all sorts of medical functions. A tiny chip-analyser could take in minuscule amounts of blood, and analyse it for such things as sugar or insulin levels.

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