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.