Biomedical Engineering Reference
In-Depth Information
Figure 3.55
Plot of the domains of self-motion in a corner, according to the Concus-Finn relations.
135°, the drop detaches from the corner and does not wet the corner anymore
(Figure 3.57).
A generalization of the Concus-Finn relation has been derived by Brakke and
Berthier in [8]. When the two planes do not have the same wettability (contact
angles
q
1
and
q
2
), the relation (3.79) becomes
θ θ π
α
+
1
2
<
-
(3.81)
2
2
Remember that
a
is the wedge half-angle. An important consequence of rela-
tion (3.81) applies to trapezoidal microchannels, a form easily obtained by micro-
fabrication (Figure 3.58).
Figure 3.56
A droplet spreads in a corner when the contact angles verify the Concus-Finn condition
(Surface Evolver calculation).
