Wheel Made of ‘Odd Matter’ Spontaneously Rolls Uphill

> When the motors are powered on, it starts writhing, executing complicated squashing and stretching motions and occasionally flinging itself into the air, all the while slowly making its way up a bumpy foam ramp

Motors. Plus the wheel is in an horizontal plane, on its side. Hence the flinging ‘into the air’. Clickbait title I think.

I would argue that this wheel isn't made out of odd matter, it's made out of motors and springs (rubber bands) the same way all actuators are. It behaves in a way that is analogous with odd matter, which the article defines as:

> The odd wheel grew out of Coulais and Vitelli’s past work on the physics of “active matter” — an umbrella term for systems whose constituent parts consume energy from the environment, such as swarms of bacteria, flocks of birds and certain artificial materials. The energy supply engenders rich behavior, but it also leads to instabilities that make active matter difficult to control.

I'm a little confused by the idea of this being spontaneous as well, especially since it's repeatable. Emergent, maybe? On the whole it just seems like a type of open loop locomotion control that doesn't rely on limit cycles. Which is interesting but not "spontaneous".

Maybe I am misreading or misunderstanding the article, but it appears that this "odd matter" is a powered, designed robot wheel with motors that cause it to roll uphill (or rather, over a hill) when powered. That doesn't strike me as either odd matter or spontaneous, or at least not in the sense that I expect from the headline.

The paper may be more interesting: https://arxiv.org/abs/2108.08837

Limit cycles turn active matter into robots

Abstract: Active matter composed of energy-generating microscopic constituents is a promising platform to create autonomous functional materials. However, the very presence of these microscopic energy sources is what makes active matter prone to dynamical instabilities and hence hard to control. Here, we show that these instabilities can be coaxed into work-generating limit cycles that turn active matter into robots. We illustrate this general principle in odd active media, model systems whose interaction forces are as simple as textbook molecular bonds yet not constrained to be the gradient of a potential. These emergent robotic functionalities are demonstrated by revisiting what is arguably the oldest of inventions: the wheel. Unlike common wheels that are driven by external torques, an odd wheel undergoes work-generating limit cycles that allow it to roll autonomously uphill by virtue of its own deformation, as demonstrated by our prototypes. Similarly, familiar scattering phenomena, like a ball bouncing off a wall, turn into basic robotic manipulations when either the ball or the wall is odd. Using continuum mechanics, we reveal collective robotic mechanisms that steer the outcome of collisions or influence the absorption of impacts in experiments. Beyond robotics, work-generating limit cycles can also control the non-linear dynamics of active soft materials, biological systems and driven nanomechanical devices.

I'm not sure why you wouldn't expect this; you're transferring energy into a motor, so it will either need to gyrate in place, or accelerate downwards or upwards up a hill.

Is it a surprising a snake can move without legs? It can't if it is dead. It needs to expend energy. This ball shaped thing isn't moving without use of energy, and isn't that surprising.

Another wheel of "an odd matter" rolling uphill: https://youtu.be/0arSdl6TjGw

Reminds me of an old site I used to love... Sodaplay or sodaconstructor... Can't remember which. You constructed little amoeba type robots, and the most simple, starting object was a very similar wheel.

Where Odd Matter is just wiggling robots.

clickbait title