The current technology relates to substrate treatments, treated substrates, and filters. Treated substrates can have a treated surface that defines a pattern and/or gradient among untreated surface areas. A treated surface area can have a higher roll off angle for a 50 μL water droplet when the surface is immersed in toluene that the untreated surface areas. Substrates can be treated by, for example, exposing a substrate surface and/or fibers to ultraviolet (UV) radiation. UV radiation can be applied to surfaces via a mask, lens, waveguide, reflector, as examples. UV radiation can be applied to surfaces at varying intensities, which can create a treatment gradient.