All living organisms – human, animal, or otherwise – continuously move molecules around their cells. It's a crucial mechanism of life, vital for feeding cells the proteins they need to function. And now scientists at Northwestern University have created a machine that mimics this pumping mechanism. Their molecular pump is the world's first such machine developed entirely through chemical engineering in the laboratory, and it could one day power artificial muscles and other molecular machines.

"Our molecular pump is radical chemistry – an ingenious way of transferring energy from molecule to molecule, the way nature does," said study senior author Sir Fraser Stoddart.

The pump uses small molecules made in the laboratory to replicate the actions of carrier proteins. It draws its power from chemical reactions, which it uses to drive molecules out of equilibrium – from a low to a high-energy state.

That extra energy is necessary to make it work because the ring-shaped molecules normally repel each other, like magnets with the same polarization. "The artificial pump is able to syphon off some of the energy that changes hands during a chemical reaction and uses it to push the rings together," explained the study's first author Chuyang Cheng.

The machine then threads the rings around a nanoscopic chain (an axle) and squeezes them together. Right now the artificial molecular pump can only force two rings together, but the researchers believe they may soon be able to make the process work with tens of rings and more energy storage.

The technology is primitive compared to the natural mechanisms of living organisms, and it will take some time for the pump to be scaled up to the point where it could power artificial muscles and other molecular machines, but it's a great step forward for what study co-author Paul R. McGonigal calls "one of the major challenges for science in the 21st century."

Stoddart also noted that the process of designing molecular machines is nothing like that of the mechanical ones we are used to seeing. "In a way, one must learn to see things from the molecules’ point of view, considering forces such as random thermal motion that one would never consider when building an agricultural water pump or any other mechanical device," he said.

A paper describing the research was published in the journal Nature Nanotechnology. You can see a video that visualizes the molecular pump process below.

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