Chemo-Sensitive Running Droplet
  Chemical control of the spontaneous motion of a reactive oil droplet moving on a glass substrate under an aqueous phase is reported. Experimental results show that the self-motion of an oil droplet is confined on an acid-treated glass surface. The transient behavior of oil-droplet motion is also observed with a high-speed video camera. A mathematical model that incorporates the effect of the glass surface charge is built based on the experimental observation of oil-droplet motion. A numerical simulation of this mathematical model reproduced the essential features concerning confinement within a certain chemical territory of oil-droplet motion, and also its transient behavior. Our results may shed light on physical aspects of reactive spreading and a chemotaxis in living things. 
Yutaka Sumino, Masaharu Nagayama, Hiroyuki Kitahata, Shin-ichiro M.   Nomura, Nobuyuki Magome, Yoshihito Mori and Kenichi Yo...