Electric field-induced chemical locomotion of conducting objects

Externally triggered motion of small objects has potential in applications ranging from micromachines, to drug delivery, and self-assembly of superstructures. Here we present a new concept for the controlled propulsion of conducting objects with sizes ranging from centimetres to hundreds of micrometres. It is based on their polarization, induced by an electric field, which triggers spatially separated oxidation and reduction reactions involving asymmetric gas bubble formation. This in turn leads to a directional motion of the objects. Depending on the implied redox chemistry and the device design, the speed can be controlled and the motion can be switched from linear to rotational. This type of chemical locomotion is an alternative to existing approaches based on other principles. External electric fields have been used to control the motion of small objects through electrostatic repulsion. Here, electric fields are used to polarize conducting objects, triggering their movement by spatially separated electrochemical reactions leading to directionally controlled bubble evolution.