Gas diffusion media for use in fuel cells are provided that contain a
pattern of deposited hydrophobic polymer such that less than 100% of the
surface of the diffusion media is covered with hydrophobic polymer. The
media are made by first wetting a sheet of carbon fiber paper in an
aqueous emulsion of the hydrophobic polymer. The wetted sheet is
contacted with a pattern member containing one or more openings oriented
to correspond to a predetermined or desired pattern of hydrophobic
polymer deposition. While still in contact with the pattern member, the
sheet is heated or otherwise treated to cause evaporation of the water
from the sheet. Evaporation while in contact with the pattern member
takes place in such a way that hydrophobic polymer is concentrated in the
sheet at the openings of the pattern member by the process of
evaporation.