Fatty Acid Chemistry at the Oil−Water Interface: Self-Propelled Oil Droplets

Fatty acids have been investigated as boundary structures to construct artificial cells due to
their dynamic properties and phase transitions. Here we have explored the possibility that fatty acid systems
also demonstrate movement. An oil phase was loaded with a fatty acid anhydride precursor and introduced
to an aqueous fatty acid micelle solution. The oil droplets showed autonomous, sustained movement through
the aqueous media. Internal convection created a positive feedback loop, and the movement of the oil
droplet was sustained as convection drove fresh precursor to the surface to become hydrolyzed. As the
system progressed, more surfactant was produced and some of the oil droplets transformed into
supramolecular aggregates resembling multilamellar vesicles. The oil droplets also moved directionally
within chemical gradients and exhibited a type of chemotaxis.