Molecular-scale dissipative chemistry drives the formation of nanoscale assemblies and their macroscale transport.

Fuelled chemical systems have considerable functional potential that remains largely unexplored. Here we report an approach to transient amide bond formation and use it to harness chemical energy and convert it to mechanical motion by integrating dissipative self-assembly and the Marangoni effect in a source-sink system. Droplets are formed through dissipative self-assembly following the reaction of octylamine with 2,3-dimethylmaleic anhydride. The resulting amides are hydrolytically labile, making the droplets transient, which enables them to act as a source of octylamine. A sink for octylamine was created by placing a drop of oleic acid at the air-water interface. This source-sink system sets up a gradient in surface tension, which gives rise to a macroscopic Marangoni flow that can transport the droplets in solution with tunable speed. Carbodiimides can fuel this motion by converting diacid waste back to anhydride. This study shows how fuelling at the molecular level can, via assembly at the supramolecular level, lead to liquid flow at the macroscopic level.