A device or system includes a mixer comprising a three-dimensional lattice defining a plurality of tortuous, interconnecting passages therethrough. The mixer is in communication with sources or streams of at least two separate components which, when mixed, form a combined fluid stream. The sources or streams may be, at least initially, on opposite sides of the mixer, or the sources or streams may be on the upstream side of the mixer with an outlet disposed downstream of the mixer. A related method may include providing a mixer comprising a three-dimensional lattice defining a plurality of tortuous, interconnecting passages therethrough, and selecting a material for the mixer based on physical characteristics of said material, said characteristics including a selected one or more of mean flow pore size, thickness and porosity volume.
