Geometrical optimization of microstripe arrays for microbead magnetophoresis

Abstract

Manipulation of magnetic beads plays an increasingly important role in molecular diagnostics. Magnetophoresis is a promising technique for selective transportation of magnetic beads in lab-on-a-chip systems. We investigate periodic arrays of exchange-biased permalloy microstripes fabricated using a single lithography step. Magnetic beads can be continuously moved across such arrays by combining the spatially periodic magnetic field from microstripes with a rotating external magnetic field. By measuring and modeling the magnetophoresis properties of thirteen different stripe designs, we study the effect of the stripe geometry on the magnetophoretic transport properties of the magnetic microbeads between the stripes. We show that a symmetric geometry with equal width of and spacing between the microstripes facilitates faster transportation and that the optimal period of the periodic stripe array is approximately three times the height of the bead center over the microstripes. V C 2015 AIP Publishing LLC.

Magnetophoretic lensing by concentric topographic cylinders of perpendicular magnetic anisotropy multilayers

“…Such a behavior is also observed for magnetophoresis experiments above engineered parallel-stripe domains. 13,19 The SPBs that are positioned on the left hand side of the structure are directed towards the center, while those to the right are continuously spread over the cylinder's perimeter (see the movie for 1 lm sized SPBs in the supplementary material). Note that some of the SPBs (the uppermost trajectory and the two trajectories below it) move along the edges of the cylinders, mainly in the region, where the edge of the structure is almost parallel to the plane of the external driving field, i.e., along the x-direction.…”

“…The periodically changing external magnetic field modulates the EðrÞ dependence by a stepwise lateral shift of the energy minima. 8,[12][13][14] In FIG. 4.…”

“…In the experiment, the external magnetic field modulates the energy landscape of the bead in a stepwise manner which affects the direction and strength of the magnetic forces acting on the SPB. 12,13,19,35 Magnetic field switching occurs with typical switching times of less than 0.5 ms (Ref. 12) and periods of 0.25 s with a constant magnetic field landscape.…”

“…[3][4][5][6][7][8] Experiments most often use micron-sized biocompatible superparamagnetic beads (SPBs) functionalized 9,10 with capture molecules to bind analytes. Besides simply using external magnetic gradient fields, like in magnetic targeting of anticancer agents to malignant tissue, 11 a more advanced way to move SPBs makes use of a superposition of substrate based local but static magnetic field sources [12][13][14] (magnetic stray field landscapes, MFLs) and temporally varying homogeneous external magnetic fields. 15 The static MFLs provided by various geometries of either topographically shaped micromagnets or artificial magnetic domain patterns possess comparably large field gradients due to small length scales, leading to significantly higher bead velocities when compared to external field gradients.…”

Investigation of injection molding parameters on the uniformity of porous array of polymer microfluidic chip

“…Lee et al [10] fabricated a disposable polymer-based microneedle array by mimicking the vibrating motion of a mosquito's proboscis. Henriksen et al [11] investigated periodic arrays of exchange-biased permalloy microstrips fabricated using a single lithography step. Until now, investigations of uniform array were mainly focused on micro array, especially for microlens array, microneedle array or nanopillar array [12][13][14].…”