Fig. 1.

Device layout and system setup. (a) Microscope image (top) showing the channel layout on an array of permalloy (Ni_0.8Fe_0.2) disks and a schematic side view of the device (bottom). Fluid flow rates Q₁, Q₂, Q₃ and Q₄ are indicated at corresponding channels while the three T-junctions are labeled with T₁, T₂ and T₃. (b) Schematic of full layout of the microfluidic channel. (c) Photograph of the device. (d) Photograph of the system consisting of four electromagnets and a solenoid that apply external magnetic field on the device. Tubings connected to computer-controlled syringes transfer fluid to or from the microfluidic channels of the device situated within the setup.