NOT only did Charles Babbage lay the foundations for the computer revolution, his designs for mechanical computers also provide a blueprint for energy efficiency. So say of Boston University and his colleagues, who have created a nanoscale mechanical logic gate that could form the basis of tiny mechanical computers.
“The mechanical logic gate is slower than its traditional equivalent, but loses far less energy”
The gate consists of a strip of silicon 300 nanometres wide sitting between two chunks of silicon. Applying a voltage between one chunk and the strip causes the strip to vibrate, like the reed in a clarinet. With the right voltage, the strip will enter a so-called hysteretic regime – where it will vibrate with one of two amplitudes.
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“The two amplitude states are separated by a potential barrier,” says Mohanty. By using a pair of electrical pulses that work with the resonating strip to provide that kick in potential, the team were able to flip the vibration from one amplitude to the other. If just one of the pulses – or neither of them – resonates with the strip then it remains in its existing vibrational state. In other words, says Mohanty, the device acts as an AND logic gate (Nano Letters, ).
While the gate is not as fast as its traditional equivalent, it loses far less energy per operation, Mohanty claims. “When you have millions of devices on a chip, energy loss adds up,” he says. Trading speed for energy might be beneficial in some situations.
