A pool of red dye is suspended in a coaster-sized maze filled with milk. Then liquid soap is dropped in, causing the dye to move, not just along the passages, but to actually “solve” the maze. It takes the appropriate directions, even making right-angle turns, until it exits the labyrinth.
How? It’s the Marangoni effect, or, what happens when you put fluids of varying surface tensions next to one another, creating a gradient of surface tensions.
And it’s all been caught on film, courtesy of UC Santa Barbara researchers, who have won an award for their efforts. Doctoral student Fernando Temprano-Coleto and colleagues demonstrate fundamental fluid mechanics in a three-minute video recognizd by the American Physical Society’s Gallery of Fluid Motion for its “combination of striking visual qualities and scientific interest.”
To view the complete story, go to http://www.news.ucsb.edu/2018/018634/soap-opera
Or look at the video directly: https://www.youtube.com/watch?v=Jtd7mMW7-0Y&t=17s