  The propagation of sound waves on lipid monolayers supported on water has
been studied during the melting transition. Since changes in volume, area, and
compressibility in lipid membranes have biological relevance, the observed
sound propagation is of paramount importance. However, it is unknown what would
occur on a lipid bilayer, which is a more approximate model of a cell membrane.
With the aim to answer this relevant question, we built an experimental setup
to assemble long artificial lipid membranes. We found that if these membranes
are heated in order to force local melting, a thermo-mechanical perturbation
propagates a long distance. Our findings may support the existence of solitary
waves, postulated to explain the propagation of isentropic signals together
with the action potential in neurons.
