Touching the quantum boundary: Scientists develop nanomotors with only 16 atoms

Empa and EPFL researchers have built the smallest nanomotors ever. It contains only 16 atoms and has even touched the boundaries of classical physics and quantum. The blue ones in the picture are six niobium atoms, red is six niobium atoms, and gray are acetylene molecules (four atoms). Like the macro-world controls, the miniature motor consists of a movable rotor and a fixed stator component.

Touching the quantum boundary: Scientists develop nanomotors with only 16 atoms

(Photo: Empa)

The stator of a miniature motor is a cluster of six niobium atoms and six niobium atoms arranged in roughly triangular shapes.

The rotor, on the other hand, is made up of acetylene molecules of four atoms, which can rotate on the surface of the stator and are less than 1 nm in size.

Molecular motors can be driven by heat or electricity, and the latter is more practical in experiments. At room temperature, the researchers found that the rotors rotate randomly back and forth.

However, when current is applied using an electron scanning microscope, the rotor can rotate in one direction at 99% stability, making it more practical than previous molecular motors.

The new mini-motor can be used not only to move small machines, but also to collect energy at the nanoscale level, the researchers said.

Touching the quantum boundary: Scientists develop nanomotors with only 16 atoms

Scanning electron microscope image of nano motors at different locations (via Empa)

The new motor also has some strange features, such as rotating in one direction in a ratchet-like manner. Usually this requires a practical gear with tilted teeth and claws, which slide along the flat side but cannot crawl back to the other side in reverse.

However, the molecules of this nanomotor seem to ignore the relatively smooth route, preferring the difficulty of the reverse challenge. Although contrary to the counterintuitive feelings of the macro world, the effect is essentially the same (rotors rotate in one direction).

此外分子马达似乎打破了经典物理学定律,因为宏观世界需要设法用最少的能量来克服阻力,比如不踩踏板就指望着自行车自己去爬坡。

The researchers found that the rotor can move even with a very small amount of heat or electrical energy — even if it is much less than the “quantity” required to rotate the rotor (meaning less than -256 degrees C / -248.8 degrees F, or applying a voltage below 30 mV).

Smallest Motor in the World (via)

Apparently, this phenomenon, which occurs in the microcosmic world, has touched the boundaries of quantum physics, and even quantum tunneling has occurred.

In fact, scientists can often observe particles ‘crossing’ obstacles without enough energy. In the case of bicycles, this is not like rushing to the top of the mountain without pedaling, but is directly transmitted to the other side of the hill.

But this explanation also raises new questions, as quantum tunneling is considered frictionless. If this is the case, the rotor will rotate randomly in any direction. But in terms of its preference for 99% probability selection, there is still energy being lost in this process.

‘This study may help us find the causes of energy dissipation during quantum tunneling,’ said lead researcher Oliver G?ning.

Details were published in the Proceedings of the National Academy of Sciences (PNAS) under the headline “Molecular motor crossing the frontier the scrotle to quantum tunneling motion”.