Simultaneous separation of different magnetic particles by sputtering magnetic wires at the bottom of a microchip: Novel geometry in magnetophoresis

Abstract

In this paper, sputtered magnetic electrodes at the bottom of the microchannel is used to separate different magnetic particles in a microfluidic device, simultaneously. The proposed design consists of a microchannel with a length of 30 mm with three different outlets. The Nickel electrodes with different angles and thicknesses are used to separate different particles. A permanent magnet is used to produce a uniform magnetic field and the presence of the magnetic wires disturbs the uniformity of the magnetic field which leads to magnetic force applied to the magnetic particles in the channel’s environment. In order to validate the results, numerical solution was compared with analytical relations. Important parameters such as microparticle size and characteristic (M−450, Myone, Oligo (dT)25), wire dimensions, wire spacing, wire angle and the flow rate were analyzed. The results show that M−450 particles are affected by greater force in comparison to Myone and Oligo (dT)25 microparticles due to their higher magnetism property and size. It was shown that by increasing the angle of the sputtered wires (at the bottom of the channel), the particle deviation was reduced. Also, the effect of wire thickness of the electrodes is investigated for thicknesses of 10, 15 and 20 μm. The maximum deviation was related to the thickness of 20 μm, thus, the particles were not able to pass off over the electrodes and moves along the wire path. By increasing the distance between the wires from 400 μm to 700 μm, the microparticle deviation was increased. As the flow rate of the inlet fluid increases (from 25 to 75 mm/s), the hydrodynamic force on the microparticles increases and therefore, the particle deviation decreases when crossing off over the electrodes. It is observed that for speed of 50 mm/s, the best separation efficiency (94%) was obtained for the proposed microchip design.