Miniature motors powered by spinning drops of liquid

If you've ever observed "wine legs," the rivulets that form when you swirl wine in a glass, you've seen the Marangoni effect. Watch how scientists are using this effect to create tiny motors that emit no pollutants.

Here's a fun explainer for young people that includes how to make a boat propelled by the Marangoni effect:

Wine “legs” and minibot motors (YouTube / American Chemical Society)

Wine image: torbakhopper