MEMS gate is logical alternative

Technology News |
By Peter Clarke

Saad Ilyas and Nizar Jaber, doctoral researchers in the laboratory of Mohammad Younis, have demonstrated that vibrating mechanical structures and switches that can be cascaded to perform complex computational operations. Gates such as AND and OR are created out of MEMS beams in which mechanical vibrations excited by multifrequency electrical inputs.

The multi-function MEMS logic device can perform the fundamental logic gate AND, OR, the universal logic gates NAND, NOR, and serve as a tristate logic gate using mixed-frequency excitation. The concept is based on exciting combination resonances due to the mixing of two or more input signals. The device vibrates at two steady states: a high state when the combination resonance is activated and a low state when no resonance is activated. These vibration states are assigned to logical value 1 or 0 to realize the logic gates. Using ac signals to drive the resonator and to execute the logic inputs unifies the input and output wave forms of the logic device, thereby opening the possibility for cascading among logic devices.

MEMS have been investigated in the past for logic operations, but it has been a challenge to devise a mode of operation that allows MEMS logic gates to be cascaded to form arbitrary computational functions.

The team demonstrated various logic operations at a single operating frequency, which is an important step towards cascading as the next milestone in MEMS resonator-based computing.

The logic gates are compatible with existing fabrication techniques. 

An electrical input causes a clamped polymer beam to vibrate at its resonance frequency. This in turn produces an electrical signal with the same frequency, which could theoretically be used as the input of another MEMS gate.

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The key advantage is whereas solid-state transistors exhibit leakage current all the time a system is under power, MEMS gates can be isolated using MEMS switches and thus only consume power during computation.

“They also require fewer gates per computing function, resulting in lower complexity, and they can be fabricated with higher integration densities – it is even predicted that these systems could be scaled down to the molecular level,” said Ilyas, in a statement.

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