Dumbbell fluidic tweezers: Enhanced trapping and manipulation of microscale objects using mobile microvortices

Mobile microvortices generated by ferromagnetic nanowires (NW) were previously reported to induce fluidic trapping for micromanipulation that can be precisely focused and translated. Based on the prototype of nickel nanowire (Ni NW) fluidic tweezers (FT), we introduce in this paper a dumbbell (DB)-like magnetic actuator assembled by a Ni NW and two polystyrene (PS) microbeads. Actuated by a weak strength rotating magnetic field (B_m<;10 mT), selective trapping and controlled manipulation of individual microobject is realized by the magnetic DB. We demonstrate that the strength and efficiency of the trapping forces generated by the magnetic DB are considerably enhanced in comparison with that using the nickel NW.