Effective-area elasticity and tension of micromanipulated membranes.

We evaluate the effective Hamiltonian governing, at the optically resolved scale, the elastic properties of micromanipulated membranes. We identify floppy, entropic-tense and stretched-tense regimes, representing different behaviors of the effective-area elasticity of the membrane. The corresponding effective tension depends on the microscopic parameters (total area, bending rigidity) and on the optically visible area, which is controlled by the imposed external constraints. We successfully compare our predictions with recent data on micropipette experiments.