Oil droplets mimic early life: Scientific American: Hanczyc's first round of experiments used nitrobenzene oil. To give the droplets a "metabolism," he put them into a highly alkaline solution (pH 12) and fuelled them with a chemical called oleic anhydride, which converts to oleic acid on contact with water. This reaction lowered the pH at the boundary of droplets, creating an uneven surface tension that caused them to move autonomously through the liquid (see video). Meanwhile, convection inside the droplets brought fresh supplies of oleic anhydride to the surface.
The droplets can "sense" their environment--moving through a pH gradient to seek out the highest possible pH (In this video, the blue dye indicates a higher pH). And by putting the fuel in the water, with a chemical catalyst in the oil, the droplets can absorb fuel from their surroundings. "You get immortal droplets," says Hanczyc. "As long as you feed them, they keep moving."