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(a) Schematic of the microelectromagnet matrix before attaching the microfluidic channel. Two layers of conducting wires are aligned perpendicular to each other, separated and topped by insulating layers. (b) Micrograph of a matrix with wires in each layer of conductors (a matrix). The width and the pitch of the wires are 4 and , respectively. (c) Cross section of the matrix along a diagonal direction. The top and bottom wires are indicated along with the substrate, two insulating layers, and the top surface. The total thickness of insulating layers was to allow the creation of a peak in the magnetic field magnitude between two adjacent wires.
(Color) Magnetic field pattern and force profile computed for a matrix and a magnetic bead. (a) A single peak in the magnetic field magnitude is shown with the currents value of each wire. Currents were optimized to generate a Gaussian shaped peak . The solid lines show wire positions and the color bar scale corresponds to the magnetic field magnitude. (b) The force on a trapped magnetic bead is shown along the dotted line in (a). A large force on the bead allows the matrix to move cells attached to the bead on the surface of the device.
(Color) (a) Scanning electron microscope image of a yeast cell (Saccharomyces cerevisiae) bound to a magnetic bead. The bead was coated with Concanavalin-A, which makes a specific binding to sugar molecules expressed on the wall of yeast cell. (b) Fluorescent microscope image of yeast cells stained with a two-color dye. Viable cells are exhibiting red intravacuolar structures whereas nonviable cells are diffusively green (Inset).
(Color) Manipulation of yeast cells by the matrix. White ticks show wire positions. Y and M indicate yeast and magnetic bead, respectively. (a) A single peak in the magnetic field magnitude was created and moved in steps less than the wire pitch, continuously transporting a single cell. (b) Cell sorting operations with the matrix. A viable cell was separated and moved away from nonviable cells by independently controlling two magnetic peaks. (c) Two cells attached to magnetic beads were trapped and rotated by applying time-varying currents to two wires crossing each other.
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