A Wheel Made of ‘Odd Matter’ Spontaneously Rolls Uphill

There is a wheel that can roll uphill by wiggling.

The ring is about 6 inches in diameter and consists of just six small motors linked together by plastic arms and rubber bands. When the motors are on, it starts playing tricks, squashing and stretching, and occasionally flinging itself into the air, as it slowly makes its way up a foam ramp.

The biophysicist who was not involved in making the wheel said it was very playful. It was a lot of fun.

Physicists are trying to get useful collective behavior to spontaneously emerge in robots assembled from simple parts that obey simple rules. Goldman is a physicist at the Georgia Institute of Technology.

One of the most important behaviors of living things is locomotion. We instinctively take these challenges in stride, but how we do this is not easy. Engineers can't program a robot to anticipate all the challenges it might encounter because they can't build one that won't collapse or lurch forward.

The odd wheel was developed by physicists Corentin Coulais of the University of Amsterdam and Vincenzo Vitelli of the University of Chicago. The wheel's uphill movement can be seen from the components. These parts don't know much about the environment but the wheel adjusts its motion to compensate.

The physicists created a ball that bounces to one side and a wall that controls where it absorbs energy from an impact. Two years ago, the researchers identified an asymmetric relationship between stretching and squashing motions as the source of the objects.

Auke Ijspeert is a biorobotist at the Swiss Federal Institute of Technology Lausanne. While their paper is being reviewed, Coulais and Vitelli didn't comment.

The new research could lead to insights into the physics of living systems and inspire the development of novel materials.

There is something odd about it.

An umbrella term for systems whose parts consume energy from the environment is what inspired the odd wheel. The energy supply leads to instabilities that make it difficult to control.

If there is a way for a system to gain energy by moving from A to B, any process that takes the system from B to A must cost equal amounts of energy. With a constant influx of energy, this constraint is no longer applicable.

In a paper published in Nature Physics in 2020, Vitelli and others began to investigate nonreciprocal mechanical properties. Nonreciprocity can be seen in the relationship between stretching and squashing motions. Fakhri is a biophysicist at the Massachusetts Institute of Technology.