title: Bidirectional microfluidic pumping using an array of magnetic Janus microspheres rotating around magnetic disks.
abstract: We demonstrate a novel, flexible and programmable method to pump liquid through microchannels in lab-on-a-chip systems without the use of an external pump. The pumping principle is based on the rotation of ferromagnetic Janus microspheres around permalloy disks, driven by an external rotating magnetic field. By placing the disks close to the edge of the microchannel, a pumping rate of at least 0.3 nL min(-1) was measured using tracking microspheres. Geometric programming of the pumping direction is possible by positioning the magnetic disk close to the side wall. A second degree of freedom in the pumping direction is offered by the rotational direction of the external magnetic field. This method is especially suited for flow-controlled recirculation of chemical and biological species in microchannels - for example, medium recirculation in culture chambers - opening the way towards novel, portable, on-chip applications without the need for external fluidic or electrical connections.
authors.affiliation: BIOS Lab-on-a-Chip Group, MESA+ Institute for Nanotechnology and MIRA Institute for Biomedical Engineering and Technical Medicine, University of Twente, The Netherlands. w.t.e.vandenbeld@utwente.nl.
authors.forename: Wesley T E
authors.initials: WT
authors.lastname: van den Beld
authors.forename: Natalia L
authors.initials: NL
authors.lastname: Cadena
authors.forename: Johan
authors.initials: J
authors.lastname: Bomer
authors.forename: Eddy L
authors.initials: EL
authors.lastname: de Weerd
authors.forename: Leon
authors.initials: L
authors.lastname: Abelmann
authors.forename: Albert
authors.initials: A
authors.lastname: van den Berg
authors.forename: Jan C T
authors.initials: JC
authors.lastname: Eijkel
mesh_terms: D008280:Magnetics; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D008863:Microspheres; D008962:Models, Theoretical; D012399:Rotation