Design and experimental proof of selected functions in implantable artificial kidney

Renal failure results in poisoning because metabolic by-products are not promptly removed from the body. The main remedy for this condition is hemo-dialysis, where blood bypasses the kidneys and is filtered in a “dialyzer”, stationary machine. This research proposes and verifies novel techniques that allow an implantable device to replace a dialysis machine. This device would perform two important kidney functions: filtering solids and retaining desired electrolytes and small proteins. Three independent approaches are proposed and experimentally verified. The first approach is design optimization of the glomerular membrane as an implantable filter to separate blood cells from whole blood. We studied the parameters that minimized pressure drop per unit area in micro-channels (straight and diverging) with circular cross-sections. The second approach, aimed at extending the filtration capability of a porous membrane, used the concept of “back-wash”. It used a natural energy source in the body, the pulsatile character of blood flow, with pressure varying between 80 and 120 mm Hg. Under similar experimental conditions, experimental results demonstrated that the permeate volumetric flow rate was higher in the backwash system compared to the no-backwash system, and this flow rate could be maintained for many more filtration cycles. The third approach, which retained body electrolytes and small proteins, used a static electric field to divert blood ions and charged proteins back to circulation. Two geometries for this electrophoretic filtration were proposed and tested: “Y” method and “cross-flow” method. The “cross-flow” method seems more promising after a preliminary comparison. A benefit of using the electrostatic deviation of charged solids before mechanical filtration is a lower density of blood solids reaching the filtration membrane, causing a lower probability of filter clogging. Due to the importance of maintaining proper pressure drops at all renal filtration stages an implantable valveless pump was designed and fabricated for pressure drop adjustments. This pump’s novelty is that it relies entirely on blood pressure pulsations and does not require an external power supply. None of the proposed filtration techniques requires external power supplies; all rely on energy delivered by the heart.