The top posts of 2007: number 3

Over the holiday period, the physics arxiv blog is re-running the most popular blogs (by page views) of 2007.

Invasion of the jivin’ nanoshrooms
24 August

Convertin’ a constant force into an oscillatin’ one is a useful trick. Ya’ll seen em: gravity-powered pendulums and wind-powered turbines for example, them both set machines a-spinin and a-swingin by exploitin’ a constant force.

Them machines might work sweetly at macroscopic scales but ain’t nobody cracked it on the nanoscale even though nanobods are a-chompin at the bit to reproduce this trick. The trouble is that gravity ain’t strong enough at this level and as for wind, who you kiddin?

That leaves only tricky-dicky forces from the dizzy world of electrostatics and magnetics and these are so poorly understood on tiny scales that them nanobods are still a-wondrin and a-ponderin over how to harness them.

But Hyun “Mighty” Kim and his crew at the University of Wisconsin-Madison say they cracked it.

Their device is a kinda nano-mushroom that stands between the plates of a capacitor, in a constant DC field.

Give the mushroom a push and it leans towards the source electrode where electrons tunnel across into the mushroom head. The DC field exerts a force on this extra charge on the ’shroom, pushing it towards the drain electrode where the electrons jump ship. The force disappears and the mushroom’s stiffness sends it swinging back to the source again like metronome, and the process starts again.

Voila! A nanomechanical oscillator that converts a a constant force into an oscillation.

Them nanobods are gonna be cockahoop over this one, betcha!

Ref: Self Excitation of Nano-Mechanical Pillars

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