Vacuum assisted slot die coating techniques

A method for applying a wet film to a substrate, comprising:

• applying a coating material at a discharge rate about 2 ml/min to about 20 ml/min from a discharge end of a slot die onto a moving web of said substrate at a moving rate of about 10.0 m/min to about 45.0 m/min to form said wet film on said substrate, said wet film including a width and a thickness relative to said substrate, wherein said discharge end of said slot die comprises an upstream bar and a downstream bar, each bar having an essentially planar land surface facing said moving web, and wherein a constant coating gap of about 40 μm to about 450 μm is maintained between said discharge end of said slot die and said moving web;
• applying a vacuum force adjacent said discharge end of said slot die, wherein said vacuum force creates a pressure differential between an upstream side of said discharge end and a downstream side of said discharge end, and wherein said pressure differential is between about 1 inch of H20 and about 10 inches of H20;
• adjusting said vacuum force in real-time while applying said coating material to control said width and thickness of said wet film;
• and
• sensing said width of said wet film, and wherein adjusting said vacuum force is performed in response to determining said width corresponds to a value other than a predetermined value.