Micromotors could give "the runs" a different meaning. Researchers just designed tiny micromotors that propel themselves through acidic environments using hydrogen bubbles. That means they can work in stomach acid.
The research group, led by University of California San Diego nanoengineering professor Joseph Wang, constructed each micromotor from extremely tiny plastic tubes containing a thin layer of zinc. The structure measures nearly 10 micrometers in length. When the engineers put the little rocket in an acidic solution, the zinc lost electrons, creating hydrogen bubbles. Then, zoom.
As the pH in the solution decreases, the rocket's speed increases. Wang and his colleagues say their micromotor can travel up to 1,050 micrometers per second, which is about 100 body lengths per second. That seems fast to me.