spaceSpace and Physics

Researchers Make Self-Moving Alcohol Droplets


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

2281 Researchers Make Self-Moving Alcohol Droplets
jytule. The pink alcohol drop can find its way through this maze to the salt solution

If you've ever wished that alcohol would just find its way to you, the following research will make you very happy. The implications could run a lot deeper than a very handy way to get drunk. 

Self-movement is usually thought of as a feature of living things or maybe robots. Dr. Martin Hanczyc however, while at the University of Southern Denmark, has made alcohol droplets not just move, but navigate their way through a maze.




"The system itself is very simple but it displays sophisticated behavior,"  says Hanczyc, now at the University of Trento. 

Hanczyc announced the experiment in Langmuir. He covered slides in an aqueous solution of sodium decanoate (CH3(CH2)8COO-Na+) and used droplets of decanol (C10H21OH) to search out the salt concentrations.


“Salt is the stimulus that makes them move,” says Hanczyc. “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.”

Given a “choice” between salt sources of different concentrations, the droplets will move towards the greater concentrations. Temperature gradients can also have an effect.

It might be more exciting if the alcohol used was ethanol, rather than decanol, a fatty alcohol that causes pain to skin and eyes. However, Hanczyc has demonstrated that the droplets are capable of carrying a payload. “The droplet can act as a carrier for chemistry that can find a target destination and release its content, such as flavoring and medicine, Hanczyc says. He also suggests that since sodium decanoate is a lubricant, salt gradients could draw it to where it is needed. 

The challenge remains as to how to create salty conditions where the droplets need to go, but Hanczyc has previously achieved similar feats with oil droplets and wonders whether this sort of self-moving behavior might once have been a predecessor to life.




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