A system includes a cylinder having a bore with a piston disposed therein, the piston moveable along the bore of the cylinder and having a passage therethrough. The system also includes a mixer disposed in the passage in the piston and including at least one porous mixing device, the at least one porous mixing device comprising a three-dimensional lattice defining a plurality of tortuous, interconnecting passages therethrough, and having physical characteristics to sufficiently mix the first and second components, which characteristics include a selected one or more of mean flow pore size, thickness and porosity.