Electropolishing of Microchannels and its Application to Dialysis System

We present a microfilter used for selective separation of nano molecular solution and separating waste, such as urea. The microfilter system consists of two layers of micro chambers made of stainless steel 316L (SS 316L) and one piece of porous membrane made of polyethersulfone (PES). The PES membrane in between two micro chambers acts as a selective separation membrane. Electropolishing technique was employed to machine the SS 316L for the structural layer in the microfilter. A method of bonding the PES membrane to SS 316L structural layers surface was developed in the microfilter fabrication, whereby diffusion test was applied in the filtering evaluation. The separation capacity of this microfilter for nano molecules size was evaluated using solution of sodium chloride and urea. The diffusion experiments indicated that the smooth surface of structural layer machined by electropolishing provides blood phase and dialysate phase flows without any difficulty at different flow rates (25, 50 and 100μL/min). The electropolishing technique used on SS 316L was regarded to be capable as the alternative options for machining, shaping and polishing other alloys material. This microfilter system with PES membrane is believed to succeed as selective separation for nanomolecular size and to have the potential use in the dialysis systems.