A single layer structure of micron or nano fibers, and a multi-layer structure of micron and nano fibers. The single layer structure of micron fibers includes a web of micron fibers and an impregnating resin, and has a pore size of 1 nm-500 nm. The web of micron fibers is formed by plural interweaved micron fibers (D≧1 μm). The single layer structure of nano fibers includes a web of nano fibers formed by plural interweaved nano fibers (D