Biomedical Engineering Reference
In-Depth Information
Figure 9.18
Principle of extraction/concentration using a combination of electrowetting and mag-
netic beads: at the end of the process (f ), the concentrated aggregate of magnetic beads attached
to target molecules can be removed with a pipette.
Figure 9.19 shows the balance of forces applied on the receding contact line. In
absence of magnetic and electrowetting forces, the balance of forces is given by the
Young law (a). The aggregate is blocked near the tip of the magnet; the shift in the
horizontal direction of the magnetic aggregate produces a horizontal magnetic force
f
x,mag
; the equilibrium position is found to give the maximum force
f
x,mag
(b). The
Figure 9.19
Balance of forces on the receding contact line. (a) Young's law in absence of magnetic
and electrowetting forces; (b) deformation of the droplet under the two actions of the magnetic and
electrowetting forces; (c) balance of the forces at the rupture limit; (d) if the electrowetting forces
are sufficient for pulling the interface and decreasing the contact angle below its limit value, rupture
inevitably occurs.
