Anisotropic surface tension of buckled fluid membranes

Thin solid sheets and fluid membranes exhibit buckling under lateral compression. Here it is revealed that buckled fluid membranes have anisotropic mechanical surface tension contrary to solid sheets. Surprisingly, the surface tension perpendicular to the buckling direction shows stronger dependence on the projected area than that parallel to it. Our theoretical predictions are supported by numerical simulations of a meshless membrane model. This anisotropic tension can be used to measure the membrane bending rigidity. It is also found that phase synchronization occurs between multilayered buckled membranes.