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Sketch of the microdevice. (a) Suspended microplate in resonance . Plate oscillation is due to Lorentz induced force from ac current flowing through the structure above an external magnetic field. (b) Edge-on view showing the sharp edges of the microplate. The sketch shows the structure, and the cavity underneath. On the upper-right, the sketch shows the sharp edge and the nonsharp edge conditions of the microplate. The length of the metal layer overhang substrate is with thickness of .
(a) Micrograph revealing counter-rotating microvortices (arrows shown) via tracer particles in water. Diameter of each vortex is of order of plate dimension . (b) Measured rotational velocity of a vortex vs excitation voltage (peak-to-peak). Frequency, or rev/s, is also shown on the right ordinate. Data suggest the microvortices are very controllable and robust.
Computational results of the microvortices. Time-mean pressure distributions are just above the plate at heights of 10, 25, and .
(a) Micrograph showing the flow with a microvortex on the right generated by a sharp edge. Movie images show 3D recirculating flow by a nonsharp edge on the left. (The 3D circulating flow is not as clear because tracer particles are drawn towards the 2D vortex on the right.) (b) Flow structure with nonsharp plate edges. Micrograph shows the tracer particles approach the plate center, then ejected outward and into the cavity prior to recirculating back towards the plate again. The inset sketches the 3D flow field. Interaction with local geometry (cavity) results in the much large (order of cavity) flow structure.
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