Controlled transport of magnetic particles using soft magnetic patterns

Abstract

Inspired by magnetic bubble memory technology, we demonstrate the temporal and spatial manipulation of superparamagnetic beads guided by soft magnetic patterns in a rotating magnetic field. Soft magnetic structures allow complex and repetitive tasks to be performed. As a demonstration, we show cyclic capture and release of antibodies from different microfluidic streams.

The effect of trapping superparamagnetic beads on domain wall motion

“…9 The force due to an externally applied magnetic field on a superparamagnetic bead below saturation conditions is proportional to both the magnetic field strength and the field gradient. This has recently been exploited by devices that manipulate beads using stray fields from localized field sources such as closure domains of patterned elements 4,10,11 or domain walls in nanowires. 5,6,12,13 If the beads are attached to cells, the use of nanostructures enables the alignment or pattering of cells, 6 providing a fundamental control over cellular organization, which could generate future tissue engineering applications.…”

Switchable Cell Trapping Using Superparamagnetic Beads

“…Therefore, superparamagnetic beads are attracted towards points where both the field and the field gradient are large. The large field gradients that occur at the edges of lithographed magnetic structures can be utilized to trap, rotate or even translate the beads across a surface under various field conditions [Mirowski 2007, Conroy 2008. As the beads may be attached to DNA strands or incorporated into cells [Tanase 2005, Mirowski 2007, Vieira 2009], this provides a mechanism of manipulating biological material.…”

“…The beads can be incorporated into biological cells without affecting cellular viability [Desai 2007] and are attracted towards magnetic poles [Mirowski 2004, Tanase 2005, Mirowski 2007, Conroy 2008, Vieira 2009. Lithographed micrometer-scale magnetic structures enable the position of magnetic poles to be controlled, providing a method of influencing the absolute position of the beads on a surface.…”

Actuation and tracking of a single magnetic particle on a chip

“…8,9 However, these techniques make use of external magnets that are difficult to integrate in lab-on-a-chip approaches. Alternatively, current carrying microwires [10][11][12][13][14][15][16][17] or on-chip magnetic patterns in combination with switching external fields [18][19][20] have been employed for localized particle actuation. A very flexible approach to control the position of magnetic particles on a chip without external magnets is given by microwire crossbar arrays as introduced by the group of Westervelt.…”