DIFFUSION ON A FLEXIBLE SURFACE

The self-diffusion of a particle on a flexible surface, such as a flui d bilayer membrane or a macroscopic interface, is analyzed theoretical ly in order to relate the macroscopic diffusion coefficient D-M, descr ibing displacements in a laboratory-fixed plane, to the intrinsic surf ace diffusion coefficient D-s and to the configurational statistics of the surface. An exact result for D-M, is obtained for a rapidly fluct uating surface. For a static surface, rigorous bounds on DM are establ ished and an effective medium approximation is derived that should rem ain accurate for strongly disordered surfaces. With the aid of these r esults, classical self-diffusion measurements can be used to study the configuration, bending rigidity, and interactions of flexible membran es and interfaces. (C) 1997 American Institute of Physics.