Makmal-Atas-Cip dengan medan magnet berkecerunan tinggi bagi aplikasi pengasingan sel biologi

Abstract

High gradient magnetic separation (HGMS) capable of producing high magnetic flux density magnitude and gradient in magnetic capturing force. Since its introductory, HGMS concept has been widely employed in the field of biotechnology, chemistry and medical. However, huge magnetic system, complicated fabrication process, inadjustable magnetic field and its gradient and Joule heating effect are some of the past research problems. In this research, a novel design of high magnetic gradient LOC magnetic separator has been simulated, fabricated and tested. This simple and easy fabricated LOC magnetic separator comprising of spiral-shaped magnet wire coil, V-shaped nickel ferrite (Ni80Fe20) magnetic core and a microfluidics channel. The V-shaped magnetic core is fabricated by KOH anisotropic wet etching of bulk micromachining and Ni80Fe20 electroplating processes. The current density of 10 - 15 mA/cm2 used in the electroplating process have successfully co-deposited Ni and Fe alloy in its stoichiometric composition of nickel 72.6 – 81.9 % and ferrite 28.4 – 18.1 %. Microfluidics channel has been successfully fabricated using replica molding technique using PDMS and PUMA polymer materials. A trapping chamber at the microchannel centre is designed to minimize the fluid velocity and thus lowering down the drag force on the magnetic microbeads. The integration of spiral-shaped magnet wire coil and Ni80Fe20 magnetic core is able to generate high magnetic fluxs magnitude of Br = 225 - 20 mT, Bz = 390 - 25 mT, and high gradient of dBr/dr = 300 x 103 - 150 x 103 T/m and dBz/dz = 160 x 103 - 80 T/m from the core hujung of size 1 – 14 516 ?m2. Moreover, tuning of the magnetic field and its gradient is enable with the electric current supplied to the magnetic system. Functional test demonstrated the 20 nm and 2.5 ?m diameter magnetic nano particles and microbeads capturing on the V-shaped magnetic core hujung. In addition, proportional relationship between the direct currect injection and the magnetic nano particles and microbeads capturing area is also observed. Joule heating effect is substantial in magnet wire coil system, however, the combination of spiral-shaped magnet wire coil of N = 20 and on-silicon chip V-shaped magnetic core has reduced the Joule heating effects of ~ 26 % at maximum direct current, IDC of 2.5 A. The reduced Joule heating effect is expected due to silicon of high thermal conductivity material enable fast heat dissipation. Magnetic beads trapping effectiveness of 100 % and 95 % has been determined using 4.5 ?m and 2.5 ?m diameter respectively at volume flow rate of 1 ?L/min using magnetic core hujung of ~ 14 516 ?m2, N = 20 and IDC = 1.0 A. The trapping efficiency is inversely proportional with the volume flow rate used in the microfluidics. In conclusion, an efficient LOC HGMS device for functional biological cells labelled with magnetic micro beads is accomplished in this study.