Biomedical Engineering Reference
In-Depth Information
Figure 3.6
Schematic view of surfactants in a liquid drop.
pure water has a surface tension of 72 mN/m and water with surfactant (Tween 10
for example) at a concentration above the CMC has a surface tension of only 30
mN/m.
In the limit of small surfactant concentration (
c
<< CMC), the surface tension
can be expressed as a linear function of the concentration
(
)
(
)
(3.6)
γ γ
=
1
+
β
c
-
c
0
0
where
b
is a constant. Equation (3.6) is similar to (3.5). We have seen how a tem-
perature gradient results in a gradient of surface tension leading to a Marangoni
Figure 3.7
Evolution of the value of the surface tension as a function of the surfactant concentration.
