May 11, 2012
Jonathan D. Posner
Mechanical Engineering, Chemical Engineering
University of Washington, Seattle, WA, USA.
Locomotion of microorganisms is commonly observed in nature. Although microorganism locomotion is commonly attributed to mechanical deformation of solid appendages, Nobel Laureate Peter Mitchell (1956) proposed that an asymmetric ion flux on a bacterium's surface could generate electric fields that drive locomotion via self-electrophoresis. Recent advances in nanofabrication have enabled the engineering of synthetic analogues that swim due to asymmetric ion flux originally proposed by Mitchell. The development of these synthetic motors may represent a step towards the development of practical nanomachines, directed drug delivery, and autonomous microsystems.
We are investigating the fabrication, locomotion physics, and engineered functionality of bimetallic synthetic nanomotors that harvest chemical energy from their local environment and convert it to useful work, analogous to their biological counterparts. Bimetallic nanorods can autonomously propel themselves at a hundred body lengths per second through aqueous solutions through electrochemical decomposition of hydrogen peroxide. These swimming motors (i) can be controlled using magnetic and chemical fields; (ii) can load, transport, and release colloidal cargo; and (iii) exhibit chemokinesis, a collective dynamic behavior similar to biological chemotaxis. Scaling analyses and computational simulations show that locomotion results from electrical body forces, which are generated by a coupling of an asymmetric dipolar charge density distribution and the electric field it generates.