How do you get a blob of oil to do tricks? Douse it with the right chemicals and it will climb steps, run back and forth along a track and even loop the loop like a roller coaster.
Kenichi Yoshikawa and his colleagues from Kyoto University coaxed a tiny oil droplet to perform these feats on narrow strips made of glass (Physical Review Letters, vol 94, p 068301). First they immersed the glass strips in water that had some surfactant in it. Next, they placed a drop of oil saturated with iodine ions onto the strip, and the blob…
