Nonlinear effects in vibrating smectic films

We observe nonlinear phenomena in vibrating smectic films. In particular, the shapes and positions of steps present in smectic films are affected by film vibrations. Above a certain threshold, we observe an instability in the meniscus consisting of the formation of a peninsula-shaped step. We point out that these effects are driven by a nonlinear inertial force which is tangent to the film surface and is proportional to the local density of the film and to the gradient of the film velocity squared.