In our previous work [R. Zhao, J. Zhou, Th. Koschny, E. N. Economou, and C. M. Soukoulis, Phys. Rev. Lett. 103,
103602 (2009)], we demonstrated theoretically that one can obtain repulsive Casimir forces and stable nanolevitations
by using chiral metamaterials if the chirality is strong enough. In our recent work [R. Zhao, Th. Koschny, E.N.
Economou, and C.M. Soukoulis, Phys. Rev. B 81, 235126 (2010)], we checked some chiral metamaterial designs and
found that the artificial chiral metamaterials constructed by passive materials is very difficult to reach the critical
chirality to realize repulsive Casimir force. Therefore, in this paper, we give a four-folded rotated Ω-particle chiral
metamaterial as an example, use the effective medium approximation to retrieval the constitutive parameters, and take
the same procedure as we did before to see how much the chiral metamaterial can reduce the attractive force. It shows
that this un-optimized chiral metamaterial can reduce the Casimir attraction by 70%.