Researchers power up gas-turbine laptops
Laptops may soon be powered by tiny engines instead of heavy batteries after researchers at the Massachusetts Institute of Technology (MIT) managed to squeeze a gas-turbine engine into a silicon chip the size of a two-pound coin.
The scientists at MIT’s Energy Research Council believe that the mini-motor could run for 10 times longer than a battery of the same weight and would be capable of powering a range of electronic devices, including laptops, mobile phones and radios.
The MIT research team, led by professor Alan Epstein of the Department of Aeronautics and Astronautics, set out to apply the gas-turbine technology that can efficiently power cities to the problem of supplying energy to portable devices. Simply making miniature versions of components such as a compressor, a combustion chamber, a spinning turbine is not feasible, but the team discovered that they could be replicated with silicon wafers.
The microengine is made of six wafers, each a single crystal with its atoms perfectly aligned to make it extremely strong. To achieve the necessary components, the wafers are individually prepared using an advanced etching process to eat away selected material. When the wafers are piled up, the surfaces and the spaces in between produce the required features and functions.
The engine works by mixing and burning fuel and air inside the combustion chamber. Turbine blades, made of low-defect, high-strength microfabricated materials, spin at 20,000 revolutions per second to produce 10W of power. And cooling, which the researchers noted to always be a challenge in hot microdevices, appears manageable by sending the compressed air around the outside of the combustor.
‘So all the parts work. We’re now trying to get them all to work on the same day on the same lab bench,’ Epstein said. ‘That turns out to be a hard thing to do.’
In parallel with traditional computer chip manufacturing, the microengines are produced 60 to 100 at-a-time from large wafers that are then cut up. This makes the engines relatively cheap to produce. However the production process will be fraught with potential problems.
‘If the wafer bonding process is done well, each microengine is a monolithic piece of silicon, atomically perfect and inseparable,’ said MIT’s Nancy Stauffer. ‘As a result, even a tiny mistake in a single component will necessitate starting from scratch. And if one component needs changing, say the compressor should be a micron smaller, the microfabrication team will have to rethink the entire design process.’
However Epstein is confident that the team will have a working model by the end of the year.