Micromixers based on chaotic advection - Micromixers Fundamentals Design and Fabrication - page 225

FIGURE 6.32

Velocity field inside a liquid plug separated by gas bubbles.

(Reprinted with permission from [39] .)

FIGURE 6.33
Direct electrowetting: (a) formation of an electric double layer at the interface and (b) an applied voltage changes
the contact angle.

where 3 0 and 3 r are the dielectric constant of vacuum and the relative dielectric constant of the
electrolyte, respectively. The higher the amount of energy stored in the capacitance, the lower is the
surface energy. The relation between surface tension and the applied voltage across the interface is
described by the Lippmann equation [43] :

2

c EDL DF

s sl ¼ s sl0 (6.25)

2

where DF is the voltage across the interface and s s10 is the initial surface tension at DF¼ 0.
Combining the Lippmann equation (6.25) with the Young equation, we obtain

s sg s sl ¼ s lg cos q (6.26)