title: Spinning Janus doublets driven in uniform ac electric fields.
abstract: We provide an experimental proof of concept for a robust, continuously rotating microstructure-consisting of two metallodielectric (gold-polystyrene) Janus particles rigidly attached to each other-which is driven in uniform ac fields by asymmetric induced-charge electro-osmosis. The pairs (doublets) are stabilized on the substrate surface which is parallel to the plane of view and normal to the direction of the applied electric field. We find that the radius of orbit and angular velocity of the pair are predominantly dependent on the relative orientations of the interfaces between the metallic and dielectric hemispheres and that the electrohydrodynamic particle-particle interactions are small. Additionally, we verify that both the angular and linear velocities of the pair are proportional to the square of the applied field which is consistent with the theory for nonlinear electrokinetics. A simple kinematic rigid body model is used to predict the paths and doublet velocities (angular and linear) based on their relative orientations with good agreement.
authors.affiliation: Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion, Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Alicia
authors.initials: A
authors.lastname: Boymelgreen
authors.affiliation: Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion, Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Gilad
authors.initials: G
authors.lastname: Yossifon
authors.affiliation: Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion, Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Sinwook
authors.initials: S
authors.lastname: Park
authors.affiliation: School of Mechanical Engineering, University of Tel-Aviv, Tel-Aviv 69978, Israel.
authors.forename: Touvia
authors.initials: T
authors.lastname: Miloh
mesh_terms: D003102:Colloids / Q000737:chemistry* / Q000528:radiation effects; D003198:Computer Simulation; D004574:Electromagnetic Fields; D004586:Electrophoresis / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D008956:Models, Chemical; D009038:Motion; D011137:Polystyrenes / Q000737:chemistry*; D012399:Rotation
chemical_list: D003102:Colloids; D011137:Polystyrenes; D006046:Gold