A channeled metal clad fiber comprises one or more surface channels that extend along directions substantially parallel to the longitudinal axis of such fiber. Metal clad fibers may include multiple protective layers, and one or more protective layers may contain multiple conductors therein. A microfibrous fuel cell structure includes a hollow microfibrous membrane separator having an electrolyte medium therein and defining a bore side and a shell side. An inner current collector formed of a channeled metal clad or unclad metal fiber, and an inner electrocatalyst layer are positioned at the bore side of such fuel cell, and an outer current collector and an outer electrocatalyst layer are positioned at the shell side thereof. Surface channels on the inner current collector provide inner fluid passages for passing a fuel-containing or an oxidant-containing fluid through the microfibrous fuel cell.