A Study of the Portable and Fully Automated Artificial Kidney

Abstract

Extracorporeal blood purification systems are essential for the treatment of renal and hepatic dysfunction, but their effectiveness depends on both biochemical toxin removal and reliable engineering performance. Conventional dialysis is effective for small water-soluble solutes, but it is limited in the removal of strongly protein-bound toxins because only the unbound toxin fraction can readily cross the dialysis membrane. In addition, compact and portable dialysis systems require stable fluid delivery, accurate flow regulation, simplified circuit setup, and integrated safety mechanisms. This thesis investigates these challenges through the development and evaluation of a portable and fully automated artificial kidney platform. The first part of this work evaluates albumin dialysis as a strategy for removing representative protein-bound toxins. An in vitro albumin dialysis circuit was used to compare polysulfone and cellulose dialyzers over a 3-hour treatment period. Indoxyl sulfate and bilirubin were selected as representative toxins, and bovine serum albumin was monitored to assess albumin retention and solution stability. Both membrane groups showed rapid initial indoxyl sulfate reduction, especially within the first 0.5 hour, followed by a slower approach toward a quasi-steady state. Bilirubin removal also occurred over the course of treatment, with the polysulfone membrane generally showing stronger bilirubin transfer at later time points. In all membrane trials, bovine serum albumin concentrations remained within a relatively narrow range, indicating stable albumin retention during the experiment. The second part of this work focuses on flow regulation in the artificial kidney system. Pump calibration experiments established a linear relationship between rotational speed and flow rate for the selected tubing and pump configurations. A closed-loop proportional-integral control strategy was then implemented to improve the stability and volumetric accuracy of the replacement and ultrafiltration channels. Open-loop operation produced persistent flow offsets and large cumulative-error drift, while pure integral control reduced drift but introduced oscillatory behavior. Optimized channel-specific PI gains provided the best overall performance, maintaining both channels close to the 40~mL/min target and limiting cumulative error without sustained drift or large oscillation. The final part of this thesis presents the design and integration of a portable dialysis prototype. The system combines a compact acrylic and 3D-printed structure, cassette-based fluidic organization, integrated scales, pump controllers, RS-485 communication, and a bubble-detection-based safety shutdown mechanism. Together, the albumin dialysis experiments, flow-control evaluation, and prototype design demonstrate the feasibility of a compact automated platform for membrane-based extracorporeal support. This work provides an engineering foundation for future development of portable artificial kidney systems with improved toxin-removal capability, fluid-control accuracy, and operational reliability.