From bead to rod: Comparison of theories by measuring translational drag coefficients of micron-sized magnetic bead-chains in Stokes flow
Fig 2
Magnetic tweezers setup for parallel translation of bead chains.
(a): Schematic representation of the magnetic tweezers with a single cone magnet, which is magnetized north at tip and south at base. (b): Finite element simulation of the cone magnet using Finite Element Method Magnetics (FEMM 4.2). Cross section of the x, y-plane through the geometric center along z-axis is shown. Field density |B| decreases from pink to blue. N and S denote north and south poles respectively. Black lines represent computed magnetic field lines. Blue dot is a schematic field of view of the 50X objective, and blue dotted lines show zoom direction. Scale bar, 5 mm. (c): A 21-bead chain in the magnetic field of a single cone magnet, aligning with the field B (white arrow) along the x-axis, and translating towards the magnetic field gradient ∇B (black arrow). The force applied to the particle is in the direction of the magnetic field gradient ∇B. Scale bar, 10 μm.