Electric field-induced chemical locomotion of conducting objects

Abstract

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.

Preparation of surface coatings on a conductive substrate by controlled motion of graphene nanoflakes in a liquid medium

“…the defects near the anode) can also be a good corrosion-inhibiting coating with a superfine abrasion performance, as reported in the previous studies [1][2][3][4]20]. 8 In general, it requires at least 10 kV high voltage to drive the large-sized particles (>200 μm) to move on an insulator substrate [12,13]. In this study, the voltage is only 24 V, but it can drive the particles (<3 μm) on the conductor surface.…”

“…The particles are more affected by Brownian motion and therefore more force has to be applied. As a direct consequence, very high external electric fields in the MV range are necessary if one wants to trigger on a water-splitting reaction on objects with a size in the nano-sized range [12]. Therefore, bubble propulsion is not playing a significant role in this study.…”

“…Therefore, bubble propulsion is not playing a significant role in this study. Additionally, the force induced by surface tension is negligible because surface tension change does not occur [12].…”

“…Moreover, if the objects are very small (typically in the micron or nanoscale), viscosity effects will become very important and therefore momentum-based propulsion (e.g. bubble propulsion produced by water-splitting or other redox reactions) is increasing difficult [12]. The friction that the particle has to overcome in order to move is amplified, due to the disadvantageous evolution of the surface to volume ratio.…”

“…In this study, the coatings of graphene will be deposited on the steel surface by means of electrophoresis. The proposed method does not require an insulated substrate to confine the high electric field (at least 10 kV) [12,13] to the fluidic layer. This method can be applied to an arbitrary conductive substrate.…”