Fibers having an electrically conductive outer surface and having an
average diameter of less than about 5 millimeters; and a dielectric
polymeric layer comprising a polymer having a main polymer chain on the
outer surface, the dielectric polymeric layer having a thickness of less
than about 50 microns, the main polymer chain comprising carbon. Fiber
transistors having an on/off ratio of at least about 10. Techniques for
making fibers and fiber transistors.