"Salt is the stimulus that makes them move. They move because the salt gradient provides a different energy landscape. It is like taking a ball that is laying still on a flat surface and then suddenly make the surface hilly. The ball will roll to the lowest accessible point. That is what the droplet is doing. Without a salt gradient every direction in which a droplet might move looks the same (flat). But with a salt gradient coming from one direction the droplet can move energetically downhill into the salt gradient. And stronger salt concentrations will attract the droplet more”, says MartinHanczyc. The system is sustainable in that the same droplet can migrate towards salts at different positions added sequentially. In addition the droplet can distinguish between salt sources of different concentration. The process can also be controlled by external temperature stimulus, and when the droplet arrives at the source it can physically fuse with it and react with it.via TechCrunch.
In what could be a useful trick for moving chemicals from one point to another, scientists at the University of Southern Denmark and Institute of Chemical Technology in Prague, Czech Republic have created a method to “move” liquids through an alcohol base. While that alone isn’t very cool, just look at the video above: in it you see a small droplet of colored water move towards two droplets of salt, navigating a paper maze on the way. This system could have been the progenitor of biological life, said the researchers. From the release: