Biomedical Engineering Reference
In-Depth Information
Figure 9.20
Assembly of parallel ferromagnetic wires in a uniform external magnetic field;
the carrier fluid circulates between the wires.
limit angle
a
of the droplet is given by the diagram (c). If the electrowetting force is
larger than the equilibrium force of diagram (c), the contact angle decreases under
the value
a
, and the droplet separates from the magnetic aggregate (d).
9.8 Example of a Separation Column
It is important to be able to remove magnetic micro- and nanoparticles from a car-
rier liquid. This process may be performed in high-gradient magnetic separators
(HGMSs). In this section, we investigate the behavior of magnetic beads submitted
to a nonuniform magnetic field in the vicinity of an assembly of ferromagnetic rods
or wires (Figure 9.20) and convected by a carrier fluid. Theoretically, this situation
is just a generalization of the example of the ferromagnetic rod. The basic equations
are the same [16].
The first step consists in calculating the magnetic field by using (9.20), then the
magnetic force field is deduced from (9.21). Figures 9.21 and 9.22 show the mag-
netic vector field and magnetic forces in the assembly of wires. Magnitudes of these
Figure 9.21
Magnetic field in an assembly of ferromagnetic wires.
