Front Cover: On‐chip control of magnetic particles (Phys. Status Solidi A 5/2012)

Abstract

During the last years magnetic micro- and nanoparticles have emerged as powerful tools in the fields of cancer treatment, bioassays, contrast enhancement or labeling on the micron- and submicron-scale. Advances in controlling the dimensions, magnetic properties, and surface chemistry of particles have opened up various new approaches, particularly for lab-on-a-chip applications. These applications emphasize the need for tools to collect and handle magnetic particles in an efficient and reliable way. Optical and magnetic tweezers fulfill these requirements but are only applicable in a limited way to on-chip experiments. Recently, microstructured conducting wires have been used to collect and move magnetic micro- and nanoparticles in lab-on-a-chip approaches. A particularly versatile architecture is given by orthogonal layers of parallel microwires on a chip surface to induce highly localized magnetic fields. Rinklin et al. (pp. 871–874) investigate different current patterns for magnetic actuation and present simple yet efficient protocols for the collection and separation of micro- and nanoparticles without the necessity of external magnets. The cover image illustrates an exemplary collection and actuation experiment. To the left, the particles are collected from a homogeneous suspension. The particle cloud generated in this way can then be moved at the chip's surface as shown in the schematic and the corresponding image series.