Tangential-flow filtration system

A tangential-flow filtration apparatus separating a fluid mixture into species of interest in a cascade mode, the apparatus comprising:

• first filtration system and a subsequent filtration system, each of the filtration systems comprising:
• a cassette formed with a layered sequence of side-by-side channels including a convergent first channel, a last channel, and, between the first channel and the last channel, series of intermediate channels, the convergent first channel and at least one intermediate channel being configured as recirculating channels having an inlet and outlet, the last channel being configured as a non-recirculating channel having an outlet;
• a series of filtration membranes, one filtration membrane positioned between each successive pair of channels in the layered sequence with each successive pair of channels in the layered sequence being separated by a filtration membrane having a successively smaller pore size;
• means for creating a flow of the fluid mixture between the inlet and the outlet of each recirculating channel of each first and subsequent filtration system in the direction of tangential flow;
• and
• means for creating a pressure differential between each successive pair of channels in the layered sequence;
• the apparatus further comprising a means for directing fluid media from the last channel of the filtration system to the first channel of the subsequent filtration system.