7 research outputs found
Flat Flow Profiles Achieved with Microfluidics Generated by Redox-Magnetohydrodynamics
Horizontal
flow profiles having uniform velocities (3–13%
RSD) at fixed heights across 0.5, 2.0, and 5.6 mm widths, with magnitudes
of ≤124 μm/s, can be sustained along a ∼25.0 mm
path using redox-magnetohydrodynamics (MHD) microfluidic pumping in
a small volume (14.3 mm wide × 27.0 mm long × 620 μm
high) on a chip. Uniform velocity profiles are important in moving
volume elements without shape distortion for assays and separations
for lab-on-a-chip applications. Fluid movement resulting from the
MHD force (<b>F</b><sub><b>B</b></sub> = <b>j</b> × <b>B</b>) was monitored with video microscopy by tracking
10 μm, polystyrene latex beads mixed into the solution. The
ionic current density, <b>j</b>, was generated in 0.095 M K<sub>3</sub>Fe(CN)<sub>6</sub>, 0.095 M K<sub>4</sub>Fe(CN)<sub>6</sub>, and 0.095 M KCl by applying a constant current across a 0.5, 2.0,
or 5.6 mm gap between an anode–cathode pair of electrodes,
consisting of one to four shorted parallel, coplanar gold microbands
[each 25.0 mm × 98 μm × ∼100 nm (thickness),
and separated by 102 μm] fabricated on an insulated silicon
substrate. By shorting the increasing numbers of microbands together,
increasing currents (118, 180, 246, and 307 μA) could be applied
without electrode damage, and the impact of ionic current density
gradients on velocity profiles over the anodes and cathodes could
also be investigated. The magnetic field, <b>B</b>, was produced
with a 0.36 T NdFeB permanent magnet beneath the chip. Data analysis
was performed using particle image velocimetry software. A vertical
flow profile was also obtained in the middle of the 5.6 mm gap