Fluid processing cassettes incorporating micro- and macrofluidic channels

A fluid processing cassette includes first and second covers, with an interior wall positioned between the covers. The interior wall includes a first surface facing the first cover and defining a portion of a plurality of macrofluidic channels. A second surface of the interior wall faces the second cover and defines a portion of a plurality of microfluidic channels. At least one opening defined in the interior wall provides fluid communication between at least one of the macrofluidic channels and at least one of the microfluidic channels. An additional interior wall may also be positioned between the covers, with each interior wall secured to a different one of the covers and to the other interior wall. The additional interior wall may be positioned between the first cover and the interior wall, with macrofluidic channels defined on each side of the additional interior wall.