Active Control of Dynamic Supraparticle Structures in Microchannels

Abstract

Paramagnetic particles in microchannels form dynamic and reversible self-assembled regularly spaced structures when exposed to an external magnetic field. The magnetically induced micron-scale patterns can be formed and reformed spontaneously, thus providing an alternative to traditional microfabrication techniques for pattern creation. Under the influence of a varying magnetic field, these structures could be rotated through all axes without loss of structural form allowing dynamic micron-scale movement without direct mechanical, electrical, or photonic interactions. The structures are not attached to the wall of the enclosure and are free to move without loss of form from both pressure-induced flow and electrokinetic effects. The dynamic supraparticle patterning can be used in an extensive variety of on-chip applications and for unique microfabrication techniques.

Magnetic bead handling on-chip: new opportunities for analytical applications

“…Despite its potential for magnetic-bead-based applications, only a few works are reported on the active manipulation of SPS composed from superparamagnetic particles inside microfluidic capillaries. Under the influence of a varying magnetic field generated by a mechanically moving permanent magnet, magnetic SPS composed of 1-2-lm diameter superparamagnetic beads could be rotated through all axes in a microfluidic channel, without loss of structural form, allowing dynamic micron-scale movement without direct mechanical, electrical, or photonic interactions (Hayes et al 2001a). A number of potential applications of this phenomenon were mentioned in this paper, like binding biomolecules on the magnetic particles for immuno-assays, studying subcellular biomechanics, and microfluidic mixing in picoliter and femtoliter volumes.…”

“…2 a Schematic diagram of a spherical magnetic microparticle with a single internal magnetic core or consisting of multiple nanometer-sized cores of diameter s. b Schematic magnetization loop of an ensemble of ferromagnetic particles, showing magnetic hysteresis. c Schematic diagram of a microparticle superstructure in the presence of a magnetic field H. When the field is removed, the particles keep a remnant moment and the superstructure does not decompose generation of equally spaced arrays of columns of chains in a microchannel (Wang et al 1994;Sandre et al 1999;Hayes et al 2001a).…”

Directed self-assembly of field-responsive fluids in confined geometries

“…[8][9][10][11][12][13] Furthermore, the study of confined self-assembly has revealed many interesting phenomena which depend on the nature of the confinement. [14][15][16][17][18][19][20][21] In the current study we will investigate the self-assembly of magnetorheological (MR) fluids in microfluidic confinement and the important role of channel topology.…”

Magnetic track array for efficient bead capture in microchannels

“…However, the complex microfabrication processes and the limited field strength (0-100 mT) are the weak points of these devices. In contrast, passive magnetic microsystems use external macro-sized permanent magnets or electromagnets [25,27,38]. The process is simplified and larger magnetic fields (>0.5 T) and forces can be reached.…”