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Spin Doctors

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Wade Hampton III

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Spin Doctors

PostMon Oct 15, 2018 11:55 pm

Scientists crafted tiny silica "dumbbells" that are too small to be seen
with the naked eye, spinning them faster than any other human-made object
on Earth.
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Spinning objects are hypnotic and fascinating, as last year's fidget-spinner
craze overwhelmingly demonstrated. But even the fastest fidget spinner trails
the new reigning champion of fast-whirling objects: a tiny dumbbell that can
rotate 60 billion times per minute.

It's enough to make your head spin.

Spin doctors — er, researchers — recently created the nanoscale rotor and
levitated it in a vacuum, blasting it with lasers to set it spinning. Their
research, described in a new study, could help reveal how different substances
respond under extreme conditions and how friction behaves in a vacuum, Tongcang
Li, an assistant professor of physics and astronomy, as well as electrical and
computer engineering, at Purdue University, said in a statement.

Over the past decade, researchers have tested the limits — and broken records —
for how fast human-made things can spin. In 2008, a motor the size of a matchbook
clocked 1 million rotations per minute, Live Science previously reported. Then,
in 2010, scientists set a new rotation record when they spun a slice of graphene
at a dizzying 60 million spins per minute, Popular Science reported that year.
Three years later, that record was shattered by a microscopic sphere measuring
just 4 micrometers — one-tenth the width of a human hair — capable of completing
600 million spins per minute, or about 500,000 times faster than the spin cycle
in a washing machine.

For the new study, the scientists tested so-called nanodumbbells made from two
joined silica spheres; each dumbbell measured about 0.000012 inches (320
nanometers) long and approximately 0.000007 inches wide (170 nm). Tightly
focused laser light can manipulate tiny objects, and the researchers tested
their dumbbells by bombarding them with circularly polarized light, which
happens when the electric field produced by the light has a constant magnitude
but its direction rotates over time. That polarized laser light forced the nanoscale
rotors to spin. In the absence of stray air molecules to slow it down — the test
was carried out in a vacuum — the tiny spinner was able to achieve rotation speeds
of 60 billion rotations per minute, which vastly exceeds what was previously
possible, the scientists reported.
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The researchers were also able to vibrate the nanodumbbell in place by blasting
it with a laser that was linearly polarized, with its light confined to a single
plane, they wrote in the study. Observations of the objects' rotation and vibration
shed light on how vacuums work, the scientists explained. People generally think
of vacuums as empty, but physicists see a vacuum as occupied by lively virtual
particles, Li said in the statement, and this research with levitating, spinning
nanodumbbells brings researchers one step closer to figuring out "what's really
going on there" on a quantum level, Li said. The findings were published online
July 20 in the journal Physical Review Letters.

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