(531g) Synthesis and Propulsion of Magnetic Colloidal Dimers Under Orthogonally Applied Electric and Magnetic Fields

Research employing particles with anisotropic shapes has shown great potential for applications such as colloidal assembly, medical therapy, microrobot design, and drug delivery. For example, polystyrene dumbbells with two different sized lobes have proven to be good candidates for active motors in response to external electric fields. However, it remains a challenge to precisely control the moving direction of dumbbell shaped particles using an electric field alone. This in turn limits further applications in which the transport and delivery of nano/micro-cargos is pertinent. On the other hand, magnetic fields have been used to induce magnetic dipole moments in magnetic materials and can align them towards a desired direction. Furthermore, compared to optical fields and other chemical-fuel driven motions, electric and magnetic fields are more biologically friendly and can be easily tuned in terms of amplitude, frequency, and field direction. As such, we use a combination of magnetic and electric fields to achieve precisely controlled motion for dumbbell shaped particles. The dumbbells are specially designed, so they have desirable magnetic and dielectric properties. The electric field generates unbalanced electrohydrodynamic flow around the two asymmetric lobes to drive propulsion, while the magnetic field will align the dumbbells along a desired direction. By tuning the strength and frequency of both fields, we demonstrate explicit control over the speed and propulsion direction of the asymmetric particle motors.