An electrokinetically driven Janus micromotor: stability and rotation
G Yossifon (Technion), A Boymelgreen (Technion), T Miloh (Tel Aviv University)
Electrohydrodynamics and electrokinetics of fluid systems
Mon 4:20 - 5:40
Barus-Holley 161
The theoretical concept of a spinning micro-motor comprising three attached metallodielectric Janus spheres (in which one hemisphere is conducting, and the other dielectric), driven using induced-charge electrophoresis (ICEP) under the application of a uniform electric field was first suggested by Squires and Bazant in 2006. The operating mechanism is based on the tendency of Janus particles undergoing ICEP to align the interface between their metallic and dielectric hemispheres to the electric field and travel perpendicular thereto with the dielectric end forward. We present here an experimental proof-of-concept for a simple Janus micromotor, consisting of only two Janus particles which are rigidly attached with an arbitrary alignment between the metallicdielectric interfaces. The Janus particles are produced by half coating polystyrene spheres with gold which ensures a large dielectric contrast between hemispheres. Upon activation of the field, the upper and lower spheres develop a velocity in the direction of their respective dielectric ends. Since the two spheres face opposite directions, the net translational velocity is zero. However, a net moment is generated around the centre point between the two spheres which causes the particles to rotate. Any misalignment between the interfaces results in a non-zero net velocity which causes the particle to orbit while it rotates. We demonstrate that a simple rigid body model can be used to provide a first order approximation for the relationship between the rotational velocity, orbits and the angle of the interfaces. Additionally, we examine the relationship between the applied field and the orbital and rotational speeds.