The hydrodynamic relaxation rate for water inhomogeneities in aligned lipid-water smectics is measured for the first time using an improved version of the "forced Rayleigh" technique. Variation of the relaxation rate with water concentration yields a distinction between "bound" and "free" water.

• Received 13 September 1977

DOI:https://doi.org/10.1103/PhysRevLett.39.1368