  The motion of an artificial micro-scale swimmer that uses a chemical reaction
catalyzed on its own surface to achieve autonomous propulsion is fully
characterized experimentally. It is shown that at short times, it has a
substantial component of directed motion, with a velocity that depends on the
concentration of fuel molecules. At longer times, the motion reverts to a
random walk with a substantially enhanced diffusion coefficient. Our results
suggest strategies for designing artificial chemotactic systems.
