Ki-Ho Han

Paramagnetic capture mode magnetophoretic microseparator for high efficiency blood cell separations

This paper presents the characterization of continuous single-stage and three-stage cascade paramagnetic capture (PMC) mode magnetophoretic microseparators for high efficiency separation of red and white blood cells from diluted whole blood based on their native magnetic properties. The separation mechanism for both PMC microseparators is based on a high gradient magnetic separation (HGMS) method. This approach enables separation of blood cells without the use of additives such as magnetic beads. Experimental results for the single-stage PMC microseparator show that 91.1% of red blood cells were continuously separated from the sample at a volumetric flow rate of 5 microl h-1. In addition, the three-stage cascade PMC microseparator continuously separated 93.5% of red blood cells and 97.4% of white blood cells from whole blood at a volumetric flow rate of 5 microl h-1.

Continuous magnetophoretic separation of blood cells in microdevice format

This paper presents a method for continuous magnetophoretic separation of red and white blood cells from whole blood based on their native magnetic properties. The microsystem separates the blood cells using a high gradient magnetic separation method without the use of additives such as magnetic tagging or inducing agents. A theoretical model of the magnetophoretic microseparator is derived and verified by comparison with finite element simulation. The microseparator is fabricated using microfabrication technology, enabling the integration of microscale magnetic flux concentrators in an aqueous microenvironment, providing strong magnetic forces, and fast separations. Experimental tests are performed using a permanent magnet to create an external magnetic flux of 0.2T, and measuring the movement of red blood cells within the microchannel of the microseparator. The experimental results correlate well with the theoretical results.

Diamagnetic capture mode magnetophoretic microseparator for blood cells

This paper presents the characterization of a continuous diamagnetic capture (DMC) mode magnetophoretic microseparator for separating red and white blood cells from diluted whole blood based on their native magnetic properties. The DMC microseparator separated the blood cells using a high-gradient magnetic separation (HGMS) method without the use of additives such as magnetic beads. The microseparator was fabricated using microfabrication technology, enabling the integration of microscale magnetic flux concentrators in an aqueous microenvironment. Experimental results show that the DMC microseparator can continuously separate out 89.7% of red blood cells (RBCs) from diluted whole blood within 5 min using an external magnetic flux of 0.2 T from a permanent magnet. Monitoring white blood cells (WBCs) probed with a fluorescence dye show that 72.7% of WBCs were separated out within 10 min in the DMC microseparator using a 0.2 T external applied magnetic flux. Consequently, the DMC microseparator may facilitate the separation of WBCs from whole blood in applications such as a genetic sample preparation and blood borne disease detection. [1574].

Reliability aspects of packaging and integration technology for microfluidic systems

This paper presents the reliability aspects of an integrated microfluidic-system-interface (MSI) technology for complex microfluidic systems. MSI technology provided three primary functional interface components: microfluidic interconnects, integrated microvalves, and optical windows. The microfluidic interconnects were designed to facilitate complex micro-to-macro fluid interfacing between the microsystem and the macro world in a single package. The functionality and reliability of the fluid interconnects were tested using standard capillary tubing. The pneumatic microvalves were integrated directly into the microfluidic interface. The valve leak-rate characteristics and the bonding stability between the integrated microfluidic interface and the microfluidic system were tested against the pneumatic-valve pressure. Use of the optical windows in the interface was demonstrated by enabling an on-chip infrared polymerase-chain-reaction (PCR) process. This paper demonstrates the use of MSI technology as a facile and reliable interface/packaging method for a complex microfluidic system.

A multi-layer plastic/glass technology for microfluidic systems with integrated functionality

A multi-layer plastic/glass technology has been developed for microfluidic systems with integrated functionality. Hot embossing and heat staking of plastics, microstenciling of electrodes, and stereolithography (SLA) was combined with conventional MEMS fabrication techniques to realize the system. The approach enables the use of multiple plastic/glass materials in a single system, provides a solution for the integration of electrical functionality throughout the system, provides a mechanism for the inclusion of microvalves, and provides an interconnect technology for interfacing fluids and electrical components between the macro and the micro worlds.

Continuous paramagnetophoretic microseparator for blood cells

This paper presents a continuous paramagnetophoretic (PMP) microseparator for directly separating blood cells from whole blood by using a high gradient magnetic separation (HGMS) method. For high magnetic separation force, the present PMP separator is fabricated by microfabrication technology, and directly separates red and white blood cells from whole blood based on their magnetic properties. The theoretical model of the PMP microseparator is derived, and simulated values are compared with calculated values. A quantitative analysis using a hemocytometer shows that 92% of red blood cells are separated from whole blood by the present PMP microseparator.

A cascade mode magnetophoretic microseparator for high efficiency blood cell separations

This paper presents the design, fabrication, and characterization of a high efficiency blood cell separator based on a cascade design of the continuous paramagnetic capture mode magnetophoretic microseparator. The PMC cascade microseparator directly separates blood cells from whole blood based on their native magnetic properties using a high gradient magnetic field without the use of additives such as magnetic tagging or fluorescent dyes. Experimental results show that 93.5 % of red blood cells and 97.4 % of white blood cells, from whole blood, was separated within 5 minutes by using a conventional permanent magnet to create an external magnetic flux of 0.2 T.

A Magnetic Microsensor based on the Hall Effect in an AC Microplasma

This paper presents a new class of magnetic microsensors based on the Hall effect in AC microplasma. In the theoretical study, we develop a simple model of the plasma Hall sensor and express the plasma Hall voltage as a function of magnetic field, plasma discharge field, pressure, and electrode geometry. On this basis, we have designed and fabricated magnetic microsensors using AC neon plasma. In the experiment, we have measured the Hall voltage output of the plasma microsensors for varying five different conditions, including the frequency and the magnitude of magnetic field, the frequency and the magnitude of plasma discharge voltage, and the neon pressure. The fabricated magnetic microsensors show a magnetic field sensitivity of 8.870.18㎷/G with 4.48% nonlinearity.