  The cosmological constant is estimated by considering the surface tension of
supervoids in a void-dominated cosmic fluid by which we can get a possible
source of dark energy. Looking at voids as bubbles, we define the concept of
surface tension which is shown to have an almost constant value for supervoids
that are enclosed by superclusters. The surface tensions of voids are computed
by dimensional method for galaxies and superclusters with different values for
each group. At large scale which vast voids are dominant the positive
cosmological constants obtained of order $ (\simeq+10^{-52} {\rm m^{-2}} )$,
which are very close to those given by $Planck$.
