Uu Matter Flow is the dynamic, spreading form of IndustrialCraft 2's UU-Matter liquid, generated automatically whenever a UU-Matter source block emits fluid outward instead of sitting still. Each Uu Matter Flow tile slides across adjacent empty blocks and cascades down ledges exactly like vanilla water, producing the moving wave a player sees while a Mass Fabricator fills a tank. Uu Matter Flow exists only in Java Edition with the IndustrialCraft 2 mod installed, and the flowing tile never appears without a UU-Matter source feeding it.

Uu Matter Flow has no use of its own beyond being the visual and mechanical shape the liquid takes in transit; the Replicator still consumes UU-Matter measured in milli-buckets, so collecting or piping the flow is equivalent to handling the source. Players lay out a Mass Fabricator above a tank so the produced UU-Matter forms a source, lets Uu Matter Flow spread into every tank cell, and then a Replicator draws the liquid back through Fluid Pipes. Because the source block regenerates from EU, the spreading Uu Matter Flow is a renewable sight in any late-stage IndustrialCraft 2 factory.