Multilayered microfilter using a nanoporous PES membrane and applicable as the dialyzer of a wearable artificial kidney

We present a multilayered microfilter for use as a dialyzer of a wearable artificial kidney separating metabolic wastes such as urea, uric acid and creatinine from blood. The microfilter device is assembled by alternately bonding chamber layers made of Ti by wet etching and semipermeable polymeric membranes made of polyethersulfone (PES) by the wet phase inversion method. The PES membranes sandwiched between each two chamber layers act as barriers to molecules larger than 1.7 nm. The multilayered microfilter was geometrically optimized with respect to our theoretical equations and experimental results in order to obtain kidney-competitive performance. Each diffusing unit of our device, which is only 24 x 24 x 0.4 mm(3) in size, was proved experimentally to be capable of allowing a flow rate of up to 1 ml min(-1) under an input pressure of only 10 kPa, which is the hydrostatic pressure in human renal arteries, while having a urea removal rate of 18 mu g min(-1).