31st August 2013

Scientists create fastest rotating man-made object

Researchers at the University of St Andrews have produced the world's fastest spinning man-made object – briefly achieving 600 million revolutions per minute.

The team was able to levitate and then spin a microscopic sphere, purely using laser light in a vacuum. This reached over 600 million RPM before it was lost from the levitation trap. This is 500,000 times faster than a domestic washing machine and more than 1,000 times faster than a dental drill.

Although there is much international research exploring what happens at the boundary between classical physics and quantum physics, most of this experimental work uses atoms or molecules. The St Andrews team aimed to understand what happens for larger objects, containing a trillion atoms or more.

To do this, they manufactured a sphere of calcium carbonate around 4 micrometres in diameter – roughly the width of a typical cell nucleus. They then used miniscule forces of laser light to hold the sphere with the radiation pressure of light, rather like levitating a beach ball with a jet of water.

They exploited the polarisation property of the laser light that changed as the light passed through the levitating sphere, exerting a small twist or torque. Placing the sphere in vacuum largely removed the drag (friction) of any gas environment, allowing the team to achieve the very high rotation rates.

As well as rotation, the team observed a “compression” of the excursions or “wobble” of the particle in three dimensions, which can be understood as a “cooling” of motion. Essentially, the sphere behaved like the world’s smallest gyroscope – stabilising its motion around the axis of rotation.

Dr Yoshihiko Arita of the university's School of Physics and Astronomy: “This is an exciting, thought-provoking experiment that pushes the boundary of our understanding of rotating bodies. I am intrigued with the prospect of extending this to multiple trapped particles and rotating systems. We might even be able to shed light on the area of quantum friction – that is – does quantum mechanics put the brakes on the motion or spinning particle, even with a near-perfect vacuum, with no other apparent sources of friction?”

Dr Michael Mazilu: “This system poses fascinating questions with regard to thermodynamics and is a challenging system to model theoretically. The rotation rate is so fast that the angular acceleration at the sphere surface is 1 billion times that of gravity on the Earth surface – it’s amazing that the centrifugal forces do not cause the sphere to disintegrate.”

Professor Kishan Dholakia: “The team has performed a real breakthrough piece of work that we believe will resonate with the international community. In addition to the exciting fundamental physics aspects, this experiment will allow us to probe the nature of friction in very small systems, which has relevance to the next generation of microscopic devices. And it’s always good to hold a “world record” - even if for only a while!”

The study was published this week in Nature Communications.

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