Abstract
Directed transport of biological species across the surface of a substrate is essential for realizing lab-on-chip technologies. Approaches that utilize localized magnetic fields to manipulate magnetic particles carrying biological entities are attractive owing to their sensitivity, selectivity, and minimally disruptive impact on biomaterials. Magnetic domain walls in magnetic tracks produce strong localized fields and can be used to capture, transport, and detect individual superparamagnetic microbeads. The dynamics of magnetic microbead transport by domain walls has been well studied. However, demonstration of more complex functions such as selective motion and sorting using continuously driven domain walls in contiguous magnetic tracks is lacking. Here, a junction architecture is introduced that allows for branching networks in which superparamagnetic microbeads can be routed along dynamically-selected paths by a combination of rotating in-plane field for translation, and a pulsed out-of-plane field for path selection. Moreover, experiments and modeling show that the select-field amplitude is bead-size dependent, which allows for digital sorting of multiple bead populations using automated field sequences. This work provides a simple means to implement complex routing networks and selective transport functionalities in chip-based devices using magnetic domain wall conduits.
Highlights
There has been considerable interest to develop faster, cheaper, and more sensitive devices for medical diagnostics and biomedical research
Designs in which a domain walls (DWs) is continuously translated while continuously binding a magnetic particle have some advantages compared to systems in which beads jump stepwise from one localized stray field source to another: higher transport speeds can be obtained by eliminating the diffusive transport step between binding sites, and particles can be more robust in, e.g., fluid flows since the particles are always magnetically bound during transport
A curved track architecture was introduced in which a rotating magnetic field can continuously drive magnetic domain walls along a track at a speed set by the field rotation rate, and that very high particle transport speeds in excess of 1000 μm/s can be obtained[22, 23]
Summary
There has been considerable interest to develop faster, cheaper, and more sensitive devices for medical diagnostics and biomedical research. Extended magnetic track structures have been introduced, which allow for one-dimensional transport and the construction of multiplexed networks[11, 15, 17,18,19,20,21,22,23, 33,34,35,36,37]. These transport systems are based on periodic, nonuniform magnetic textures or propagating magnetic domain walls (DWs) that lead to either stepped or continuously translating potential energy wells www.nature.com/scientificreports/. A curved track architecture was introduced in which a rotating magnetic field can continuously drive magnetic domain walls along a track at a speed set by the field rotation rate, and that very high particle transport speeds in excess of 1000 μm/s can be obtained[22, 23]
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