NOVELTY - A sprayable ink, comprises a) catalyst particles (40); b) polymer electrolyte ionomer (38); and c) a vehicle (42) for dispersing the catalyst particles and the polymer electrolyte ionomer, where the catalyst particles have a d50 (median particle size) that does not increase by more than 10%, measured 24 hours after high shear mixing.    USE - As sprayable ink for forming catalyst coated membranes (claimed) useful in fuel cells e.g. direct methanol fuel cells.    ADVANTAGE - The ink has a viscosity of not greater than 25 cP; and has a total solids loading of 5-20 wt.%. The inks is effective for forming CCMs (catalyst coated membrane) and MEAs (membrane electrode assembly) having desirable physical properties, e.g., porosity, for maximizing contact between the fuel cell reactant, e.g., methanol, the catalyst particles, and the PEM (polymer electrolyte membrane) at the so-called 3-phase interface. The method maximizes the concentration of the three-phase interfaces within a MEA (membrane electrode assembly) and thus improves fuel cell efficiency. The method prepares a catalyst coated membrane having desired catalyst layer porosity. The sprayable ink have a high concentration of catalyst particles, and which have a long shelf life with little or no settling of catalyst particles. The average settling velocity of the particles is low such that the suspensions have a useful shelf life without the necessity of frequent mixing. The vehicle imparts physical characteristics such as surface tension, viscosity and solids loading, to the ink composition. The methods using spray devices allows not only the flexibility to produce the patterns required to achieve the structures indicated but enables the spraying of multiple layers in which the drying characteristics can be carefully controlled. The digital spraying enables the deposition of materials on a substrate without direct human interaction. This increases safety in the manufacturing facility by minimizing human interaction with machinery and harmful chemicals. Minimizing human interaction with the manufacturing process also eliminates the probability of human error during spraying. The digital spraying makes the manufacturing process easier and more cost-effective.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) forming a catalyst coated membrane involving: c) depositing an ink comprising catalyst particles and a vehicle onto a membrane (8); and d) vaporizing the vehicle (40-90 wt.%) from the sprayed ink under conditions to form a catalyst layer (6, 10) on the membrane, where steps (c) and (d) are alternated to form multiple stacked catalyst layers on the membrane;    (2) forming a catalyst coated membrane having a desired catalyst layer porosity involving: f) providing a correlation between catalyst layer porosity and membrane temperature; g) employing the correlation to determine a target membrane temperature based on the desired catalyst layer porosity; h) heating a membrane to the target membrane temperature; and j) depositing an ink comprising catalyst particles and a vehicle onto the heated membrane, where the heated membrane vaporizes the vehicle and forms a catalyst layer having the desired catalyst layer porosity; and    (3) a catalyst coated membrane comprising a polymer electrolyte membrane having a first surface and a first catalyst layer disposed on there, where the first catalyst layer has a porosity gradient in which porosity increases in a direction extending away from the first surface.    DESCRIPTION OF DRAWING(S) - The figures show a schematic views of spraying sprayable catalyst ink e.g. anode or cathode ink, on a membrane using a spraying nozzle.    catalyst layer (6,10)    membrane (8)    polymer electrolyte ionomer (38)    catalyst particles (40)    vehicle. (42)