Well this is something you certainly don't see every day. It's a tiny droplet of alcohol that's autonomously navigating a maze in an effort to reach a target. The researchers who set up the experiment say it could lead to some interesting new technologies.
We don't typically think of droplets — simple spheres of fluid — as the most dynamic things in nature. Typically, the ability to self-move is an attribute reserved for living organisms. But as new research from the University of Southern Denmark and the Institute of Chemical Technology in Prague, Czech Republic, demonstrates, non-living entities can move to.
Now it might not seem like a big deal, but the ability to coax the movement and directionality of droplets — in this case a tiny ball of decanol — may be used as a technology to physically move chemistry to a place where it's needed. For example, it could act as a lubricant, targeting an area in a machine. Or, the droplet could be used as a carrier for critical chemical agents; once the parameters are set it, droplets could be used to find a destination and release its content, such as medicine or even flavoring.
The key ingredient to the process is salt, which attracts alcohol. It's the stimulus that makes the droplets move. And they move because the salt gradient provides a different energy landscape. Lead investigator Martin Hanczyc put it this way in a University of Southern Denmark release:
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.
The system is also sustainable; the same droplet can migrate towards salts at different positions when added sequentially. Also, it can distinguish between salt sources of different concentrations and be controlled by external temperature stimulus. What's more, the droplet can physically fuse with the destination object on arrival and react with it.
Read the entire study at Langmuir: "Dynamics of Chemotactic Droplets in Salt Concentration Gradients".
Image: Čejková et al/Langmuir