A microfluidic system for separating malaria-infected red blood cells using a magnet array

Abstract

This thesis aims to develop a lab-on-a-chip technology which could reduce diagnostic time and eases of use for malarial-infected erythrocytes separation. The principle relies on their magnetic properties which distinguish from common erythrocytes. The mathematical model of infected erythrocytes is developed to predict the trajectory influenced by the magnetic field. The methodology of the study is to use Finite Element software, COMSOL Multiphysics, for clarifying the magnetic field distribution from a magnet array. With the array, the high gradient of magnetic field as well as the magnitude of the force exerting on the erythrocytes could be enhanced. After that, the trajectory of the erythrocytes due to the exerting force is computed using Finite Difference with Matlab programming. To validate the model, experiments with magnetic beads have been performed. The device used in the study consists of 500 micrometer in width, 100 micrometer in height, three inlets and two outlets, and magnet array placing beside the channel. In experiments for 5 and 10 micrometers of magnetic beads, the model to predict the trajectory has an error about 18.61% and 17.61% respectively. The error stems from the non-uniform distance between the magnet array and bead-focusing stream due to the poor precision of the fabrication and a difficulty to identify a plane of motion of particles due to relatively long focal-depth of examined images in the experiments. In the case of blood experiment, this study has used P.Berghei-infected mouse blood. The model suggests that infected cells should move laterally about 36.44 micrometers under flow rate of 0.2 microliter per minute within the downstream of 3 cm when the cells are far from the magnet of 600 micrometers at the beginning. In the experiment, due to cell diffusion at low flow rate, it is hard to observe the motion within this short distance clearly under the microscope.